Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
Get a Cloudy Nights T-Shirt Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green GuÖ uh, User

Equipment Discussions >> Cats & Casses

Pages: 1 | 2 | 3 | 4 | 5 | (show all)
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Same battery for mount and dew system?
      #5514437 - 11/11/12 12:54 PM

I bought the ScopeStuff dual outlet cigarette lighter adapter with digital voltage gauge to use to power my CG5 or CGEM mount with my DewBuster controller. I have since been told NOT to do this because it could damage my mount. Is this true? Is anyone else doing it this way? Thanks

Post Extras: Print Post   Remind Me!   Notify Moderator  
wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5514650 - 11/11/12 03:25 PM

how could it damage your mount if you are using the proper fuses inside the cig adapter? Won't pull enough current?

Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: wolfman_4_ever]
      #5515117 - 11/11/12 09:31 PM

Quote:

how could it damage your mount if you are using the proper fuses inside the cig adapter? Won't pull enough current?




I dont know, that is my question. I believe he said voltage spikes could damage the electronics in the mount.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Arizona-Ken
Pooh-Bah


Reged: 08/31/08

Loc: Scottsdale, Arizona
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5515335 - 11/12/12 12:10 AM

Absolute wackery.

I have used dew control on my CG5 and CPC mount for years with no problem.

Arizona Ken


Post Extras: Print Post   Remind Me!   Notify Moderator  
wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Same battery for mount and dew system? new [Re: Arizona-Ken]
      #5515353 - 11/12/12 12:22 AM

The current will fluctuate when it's pulsing but it's in the tenths range.. nothing you will notice..

Post Extras: Print Post   Remind Me!   Notify Moderator  
DwainM
member


Reged: 07/30/12

Loc: NW AR
Re: Same battery for mount and dew system? new [Re: wolfman_4_ever]
      #5515611 - 11/12/12 08:33 AM

+1 to Dave's comment.
I've been using two small lawnmower style batteries with volt and amp meters connected and all you see is a pulsing current when the controller is duty-cycling the heaters.
I bought into the same line of thought but I've seen no evidence of anything that would cause a problem with the mount.
Dwain


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: DwainM]
      #5515648 - 11/12/12 09:16 AM

Anyone else heard of this? OK, I will name drop, I was told this by Dr Clay Sherrod. I'm sure he knows what he is talking about. He told me "Do NOT use the same battery for your mount and dew control...." It sure would be more convienent for me to use just 1 battery. That is why I bought the dual outlet cig plug.

Post Extras: Print Post   Remind Me!   Notify Moderator  
DwainM
member


Reged: 07/30/12

Loc: NW AR
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5515668 - 11/12/12 09:39 AM

Wow. My first post and I kicked the shin of a legend....
I'll be popular.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: Same battery for mount and dew system? new [Re: DwainM]
      #5515865 - 11/12/12 11:54 AM

The only problem I see is the dew heaters could drain the battery so that the voltage becomes too low for reliable mount operation.

I would be surprised to see voltage spikes measured across the battery terminals .

If powering a goto mount,dew heaters,and active cooled cameras a large capacity battery pack is a very good idea.Some of the booster packs have only a 7AH battery inside ,better is one with a 15AH or 17AH .It will cost more and weigh more but will be more reliable.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: BigC]
      #5516205 - 11/12/12 03:25 PM

Quote:

The only problem I see is the dew heaters could drain the battery so that the voltage becomes too low for reliable mount operation.

I would be surprised to see voltage spikes measured across the battery terminals .

If powering a goto mount,dew heaters,and active cooled cameras a large capacity battery pack is a very good idea.Some of the booster packs have only a 7AH battery inside ,better is one with a 15AH or 17AH .It will cost more and weigh more but will be more reliable.




I use a full size car battery


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: DwainM]
      #5516215 - 11/12/12 03:29 PM

Quote:

Wow. My first post and I kicked the shin of a legend....
I'll be popular.





HAHA! Its ok, I kinda set you up for that...Sorry. I'm still not convinced of this though which is why I asked the question here. Since I use a full size car battery maybe it will be ok? I just dont want to take any chances with my CGEM DX and CG5 mounts. I should try to get back in touch with him again and get some clarification on this though it seems many havent had a problem.

By the way...Welcome to Cloudynights!! I see you are right up the road from me


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516241 - 11/12/12 03:48 PM

Ok, I just sent him another email so hopefully I'll get some explaination on it soon. Actually I was hoping to hear what I have so far (that it is fine to use 1 battery). It sure would make things easier on me. I'm also hoping Uncle Rod will chime in with his thoughts.

Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516267 - 11/12/12 04:03 PM

I always use a single battery to run my mount (CG5, Atlas, CGE, Nexstar SE) and dew controller. Never an issue in decades. I use a splitter as you describe. I also use quality batteries (Optima deep cycle blue tops).

- Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: jrbarnett]
      #5516297 - 11/12/12 04:32 PM

Quote:

I always use a single battery to run my mount (CG5, Atlas, CGE, Nexstar SE) and dew controller. Never an issue in decades. I use a splitter as you describe. I also use quality batteries (Optima deep cycle blue tops).

- Jim




Good to hear Jim! I'm hoping I've been worrying about it for nothing and can get back to using 1 battery.


Post Extras: Print Post   Remind Me!   Notify Moderator  
DwainM
member


Reged: 07/30/12

Loc: NW AR
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516337 - 11/12/12 05:10 PM Attachment (26 downloads)

Thanks! Itís good to be here.
Actually my battery box is rather convenient with the two lawnmower battery set up.
Iím not doing AP (yet) so my power needs are pretty low.
Here is a picture of how both batteries fit neatly inside of one Group27 battery box.

Dwain


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: DwainM]
      #5516502 - 11/12/12 06:46 PM

Just heard back from Dr Clay...I believe I'd rather be safe than sorry. He said I WILL eventually end up with a voltage spike of 40 volts or more if running more than one thing off a single battery. Some of you may be lucky but lucky has NEVER been associated with me so I think I will take his advice.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516676 - 11/12/12 08:28 PM

The funny thing here is that the most likely thing to cause a voltage spike like that are the motors in the drive itself. The heaters draw a good amount of current, but shouldn't be highly inductive. However, every time a motor cuts off there's a nice big reverse EMF spike. Diodes on the drive circuits are usually used to damp that down, and similar tricks could be used on the heater coils. There's no doubt that the more things that are connected, the higher the chance that something could go wrong, but I doubt those chances are all that high. Likewise a lot of people have the same fear about AC supplies and although I've never had a problem with any of mine, that doesn't mean it's not possible. Still, I suspect that most electrical damage to control circuitry in mounts has been due to ESD from the user in the nice dry cold air. And of course the ESD can damage a power supply and then cause havoc on what it's powering too!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516681 - 11/12/12 08:30 PM

I have no knowledge of battery operation so I am curious how you get 40 volts out of a 12 volt battery?

Post Extras: Print Post   Remind Me!   Notify Moderator  
rmollise
Postmaster
*****

Reged: 07/06/07

Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516704 - 11/12/12 08:40 PM

Quote:

Ok, I just sent him another email so hopefully I'll get some explaination on it soon. Actually I was hoping to hear what I have so far (that it is fine to use 1 battery). It sure would make things easier on me. I'm also hoping Uncle Rod will chime in with his thoughts.




It IS possible to introduce some noise from the dew heater, which COULD bother a computer, I reckon. But the only problem of this sort I have ever had with a dew controller is creating interference on the Stellacam or Mallincam video cameras when I've run them and the heater off the same battery.

Still, I run the scope off a different battery to avoid _potential_ problems and to keep the battery up enough to run the go-to scope reliably. Many go-to mount problems caused by low voltage there are...


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: rmollise]
      #5516716 - 11/12/12 08:48 PM

Quote:

Still, I run the scope off a different battery to avoid _potential_ problems and to keep the battery up enough to run the go-to scope reliably. Many go-to mount problems caused by low voltage there are...




Yeah, following up on my last post, both switching power supplies and motors have the general behavior that the lower the voltage of the power supply, the more current they draw. The higher the current, the higher the back EMF when things switch. So actually a low battery can cause more problems than a fully charged one, and not just due to the dipping supply.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Eddgie
Postmaster
*****

Reged: 02/01/06

Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5516750 - 11/12/12 09:04 PM

Well, I don't know what Dr. Clay is a doctor of, but my guess is that it is not Electronic Engineering.

I have a double E.

There is no way to get a 40 volt spike out of a 12 volt battery.

I am not a Dr., but have 20 years of experience with electronic (Aviation Electronics - Fire Control Radar and Navigation/Communication electrons, and 10 years as a field engineer with IBM).

You are not ever ever ever going to get a 40 volt spike out of a 12 volt battery.

Now if it were an unregulated power supply, I would say "Maybe" (though it would be a very rare occurance even in an unregulated power supply) but a battery is not an unregulated power supply.

A battery can only produce its rated voltage. Never more, but often less.

There is this though. A big dew strip (like for a C14) draws about 4 amps.

The most common dew controllers use a timer that cycles the power strip on and off. Some people beleive that the knob regulates the heat by regulating the current to the strip directly, but it does not.

The knob controls a timer circuit that cycles the strip on and off. If you turn the knob to a higher position, the on/off cycle becomes longer.

This means that it is either drawing full current or no current.

Let's say that your strip draws thee amps, but you have your controller set to 1/3rd level. At this setting, your controller might cycle the strip on for 3 seconds, then off for 6 seconds. For the three seconds it is on, it is drawing the full 3 amps. For the 6 seconds that it is off, it is not drawing any current.

This means that at this setting, it will draw 3 amps for 20 minutes out of the hour, or one amp per hour.

A Go-To telescope will usually draw 2 amps when slewing and about .8 amps when tracking.

But you always have to plan your power for your peak draw and for your amperage load.

This means that your wiring needs to be capable of handling the full amperage draw of the dew strip and of the telescope when slewing.

If you run your scope from a battery, you will need to ensure that the wiring that goes to the socket can handle the current (and my guess is that for a medium size Go-To scope and dew strip this will be about 4 amps) and that you have a fuse in the line that is rated for the peak current. Do not wire direclty to the battery. You really want to fuse the circuit on the hot side with a fuse that is about 1.3x the expected load. So, if you expect a peak draw of 4 amps, you would want to use a 5 amp fuse.

Next, you need to calculate the amount of time you think the dew strip will be on and calculate the amp hours of the battery. Again, a Go-to scope will draw about .8 amps while tracking, but 2 to 2.5 amps while slewing (depending on the scope), but over an hour, figure you will draw about 1.5 amps out of the battery to run the scope.

For the dew strip, again, the strip will never draw over it's rated current (which again depends on how long the strip is) but if you have to turn it up high, this means that you will draw that 3 amps for a bigger and bigger percentage of the hour.

If your conditions are bad, this means that you may be running the strip with fairly high amount of on-time.

If the on cycle of a 3 amp strip is 66%, then you will draw 2 amps from your battery for an hour, plus perhaps another 1.5 amps for the scope.

This means that you will need to plan on a battery that will provide about 3.5 amps per hour of operation.

And here is the bad part. While it is very unlikley that you will damage the scope, here is what will happen to a Celestron controller if the voltage of the battery falls off (which causes the current to fall).

When slewing, the scope will start to audibly bog down. As the dew strip kicks on and off, you will hear the motor speed up and slow down.

This is the exact opposite of what Dr Clay is saying. You don't get volatage spikes, but rather you get voltage dips.

I get them all the time, and it has never damaged a controller.

My bet (and it is only a bet) is that the LEDs for the emitters are not getting sufficient voltage and the emmitters loose position. The sensor does not see any pulses so the motor keeps turning.

Agian, this does not appear to hurt anything (I have had it happen many times) but it does mean that you loose your alignment and have to re-align (assuming that you have another power source).

Bottom line.. If you think your current draw is about 4 amps per hour and you want to run your scope for 3 hours, I would recommend that you provide at least 50% reserve capacity. This means that if you anticipate a draw of 12 amps for 3 hours, you should bring a 24 amp battery to the party (Lead-acid). This is because as the charge on lead-acid batteries gets lower, the volate goes down.

Once the voltage drops below about 10 volts, when the dew strip controller shoots the current to the strip, you will get a brief volatage drop. If the scope is slewing, you will know when you are there, because the slew will start to slow down and then speed up as the strip cycles off again.

When this happens, it is time to quit.

Again, I have had this happen many many times, but it has never hurt anything.

My advice though is to run on the mains whenever you can. Even if you have to set uncoil a 75 foot extension cord, it is actually almost easier than messing with a battery.

Of course if you are going remoted, you have little choice, but I usually just run off of the car battery, making sure that the accessorys are off (in particular the blower fan for the A/C or heater) and being sure to start the car every half hour or so to keep the battery from going dead (and yes, it happend once.. Left the fan running for 2 hours... click click click.. Bummer).

So dude, if Dr Clay scared you, I am sorry to hear that, but my experiecne and my electronic background both say that this myth is busted.

You can run both your scope and your dew strip from a bettery and you are not going to get a 40 volt spike.


Post Extras: Print Post   Remind Me!   Notify Moderator  
wiruna
member


Reged: 08/11/06

Loc: Sydney, Australia
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5517228 - 11/13/12 03:09 AM

FWIW Astro-Physics are pretty emphatic in their manuals that the mount should have its own dedicated power source.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Paul G
Post Laureate
*****

Reged: 05/08/03

Loc: Freedonia
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5517314 - 11/13/12 06:10 AM

I run my mount and dew heater off the same battery, no problem.

Post Extras: Print Post   Remind Me!   Notify Moderator  
wiruna
member


Reged: 08/11/06

Loc: Sydney, Australia
Re: Same battery for mount and dew system? new [Re: Paul G]
      #5517377 - 11/13/12 07:46 AM

Actually, I raised this question on the ccd new-astro yahoo group and there was quite an informative discussion. See this thread http://tech.groups.yahoo.com/group/ccd-newastro/message/71590
Geoff


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: Eddgie]
      #5518672 - 11/13/12 08:47 PM

Quote:

There is no way to get a 40 volt spike out of a 12 volt battery.




Not directly, no, but remember, the OP wasn't going to hook the two different loads directly to a battery. He was going to use a dual lighter adapter connected to the battery (or whatever power source) and plug his devices into that. This is where the potential trouble starts. While the voltage across the poles of the battery may not deviate (much), there's resistance and inductance in the leads to the splitter. That WILL allow the voltages at the feeds of the two devices to deviate from the battery voltage. How much depends on the loss (no big deal, just a reduction in power) and the combination of the inductance and the current being switched on and off. It's that switching off of a high current that's the killer. Once you get a current flowing, it wants to continue flowing. This is what causes arcing when you flip off a switch and why we have fancy things like zero crossing breakers and other tricks to blow out the arc on a breaker when it trips due to too much current. The higher the inductance and the more current flowing, the higher the voltage spike when you suddenly try to turn it off. That can get high enough to break down the dielectric of air and cause arcing. That generally doesn't happen when you turn something on, but only when you turn it off. Arcing you notice when plugging something in is actually due to temporarily making then breaking the connection. It takes about 3 kV/mm to break down the air dielectric, so your 12V supply or even 120V AC won't do that except over microscopic distances. However, yank a plug out of the wall while you're running a high current load and you'll see plenty of sparks, assuming you catch the A/C wave near full current.

At any rate, if you want to be safe(safest), make completely separate connections at the battery.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
bluedandelion
Carpal Tunnel
*****

Reged: 08/17/07

Loc: Hazy Hollow, Western WA
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5518731 - 11/13/12 09:25 PM

Manufacturers do have a warranty to service, so they will point you to the safest (not necessarily the most convenient) ways to operate their devices to avoid lawsuits.

CCD makers asking for a separate battery is probably for a different reason. There were some reports that radio interference from dew heaters caused noise in cameras. How widespread this was I have no idea. I have not seen this in my own work.

It is well documented that some CCD cameras (Atik 383, see Atik forums) do not work to specs at low voltages. Most 12V devices work just fine with voltages as low as 11.5V but the Atik 383 becomes very noisy if the voltage dips below 12V. Most owners have purchased a regulated supply to solve this issue.

The mount issue can only be a fear of inductive back voltages from the drive motors. No need to speculate, it's an easy thing to see if you have an oscilloscope. Hook up your mount and look for voltage spikes across the battery terminal as you slew. Any volunteers? I don't have an o'scope.

Ajay


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: bluedandelion]
      #5518769 - 11/13/12 09:52 PM

On the CCDs, low voltages will reduce the effectiveness of the Peltier coolers and may just increase thermal noise rather than (or in addition to) any electrical noise.

Beo

Edited by Lord Beowulf (11/13/12 11:09 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: bluedandelion]
      #5518772 - 11/13/12 09:56 PM

After reading this whole thing, I've decided never to plug any of my gear in again. I guess I better get a big ol' dob on a non-go-to mount.

Sigh...and I was just getting into AP....

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
bluedandelion
Carpal Tunnel
*****

Reged: 08/17/07

Loc: Hazy Hollow, Western WA
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5518950 - 11/14/12 12:23 AM



It has not been a problem for me. I am not going to carry five batteries into the field for five devices. Reasonable precautions like having fuses and modern electronic design should take care of most likely scenarios.

Could we have even hearsay evidence (not theoretical possibilities) of mounts or other devices kicking the bucket because they were plugged into the same battery?

Ajay

Edited by bluedandelion (11/14/12 12:24 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
rigel123
Postmaster
*****

Reged: 06/29/09

Loc: SW Ohio
Re: Same battery for mount and dew system? new [Re: bluedandelion]
      #5518990 - 11/14/12 01:42 AM

I use two 35 amp hour batteries in the field. One for my mount and CCD and one for my dew strips and to plug in my computer when I'm switching batteries and I have not seen any issues.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Eddgie
Postmaster
*****

Reged: 02/01/06

Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5519219 - 11/14/12 09:03 AM

I have used a three way splitter for years.

There is no "Inductance" in a splitter. Inductance takes a coil, and these devices do not use coils. They simply have buss bars to distrubute the voltage to the different sockets.

And inductance by itself will not cause a spike that is bigger than the voltage put into it.

In other words, if you pass current though a coil, and then remove the current, when the field collapses, it can induce a current into a nearyby coil.

If the nearby coil has more widings than the first coil, you can get more voltage out of the second coil than you put into the first coil. This is a "Step-Up" transformer.

If the second coil has fewer windings, you get a step-down transformer.

But even here, the amount of induction is tiny. So, to get enough efficiency, you need a bunch of steel plates that carries the magnetic force efficiently betwen the coils.

This is why transformers are so big and heavy.

So, there really isn't any mechanism in a splitter that would allow the voltage to triple.


The last method would be a pulse forming network where you use inuctance and capacitance together to build up a large charge so you can discharge it at once. Radars used to use these pulse forming networks, but they are generally large and expensive, and not typically found in 12 volt splitters.

This is what my electronic engineering education and background would have to say on the topic.

You can't get a 40 volt spike out of a baattery, a splitter, or a battery/splitter combination.

To get more voltage than you have from a battery, special circuitry would be required, and this circuitry is not inside of a splitter. They are simple devices with little or no electonic circuitry.

Sorry, but I strongly believe that the OP is being given bad advice on the "Don't run booth of a battery because of 40 volt spikes" point.

If he wants to run it this way, he will not damage his mount because of spikes. There is not a mechanism in the battery or splitter that would allow for the voltage to go over the rated voltage of the battery.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: Eddgie]
      #5519372 - 11/14/12 11:13 AM

"Using the same battery for dew heat as well as powering your scope will eventually provide you with spikes up to nearly 40 volts or more. Enough to take out all of your electronics immediately.
But, what do I know? I have already given you my advice: batteries are cheap, power sources are cheap and if you use unregulated and dual-operational power along with your electronic mount you WILL ultimately end up with dead components. Maybe not now, maybe not until 2014, but you will end up with a spike."

"If using DC battery power, the current is regulated naturally and will not spike unless you have other devices connected to the same battery.
Regulated would be if you are using an AC-to-DC converter."

I do not use an AC to DC converter. I only use a full size car battery. Going by what he says would I be ok to ditch the splitter and wire in a seperate cigarette lighter plug? No disrespect to anyone here because you have been at this much longer than me but I'm sure Dr Clay has his reasons for telling me this and knows what he is talking about. I just DO NOT want to take any chances with my equipment because I cant just run out and replace it the next day if it tears up

This is the splitter I'm using and here is the battery.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5519377 - 11/14/12 11:15 AM Attachment (16 downloads)

Hmmm...for some reason the pic didnt come up. I'll try again. I can easily wire in another plug next to the one I already have if the splitter is what he's saying could cause the problem. From what I understand he's saying a 12v battery IS regulated unless something else is plugged into the same socket?

Edited by rflinn68 (11/14/12 11:17 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Eddgie
Postmaster
*****

Reged: 02/01/06

Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5519398 - 11/14/12 11:29 AM

Batteries are batteries. They never produce more then their rated voltage.

The only way to get more voltage than the battery can provide would be to use some kind of electrical circuit to build up a charge (a pulse forming network using capacitors and inductors working together) or a transformer, which is only used with AC power.

I do not know what DR. Clay is a doctor of, but as an electronics engineer, I would say that however he came by this position, it is in error.

Anyone that has a formal education in electronics engineering would tell you that you can't get a 40 volt peak from a 12 volt battery/splitter combination. There is no mechanism to amplify the volatge over the 12 volts that the battery can provide.

To get a higher voltage, you need some circuitry to create it and none exists in this configuration.

But I don't care what the OP does really. If Dr Clay scared him bad enough with this information that he will base his telesecope buying decision on this information, that is his problem.

For the rest of the people that are using this and not experiencing problems, you can rest assured that there are not going to be any 40 volt spikes due to running a dew heater off of the same battery as the telescope even if using a splitter.

If that were the case, my guess is that we would have many many reports of burned out hand controllers from people doing it, and as best as I know, I have not seen this reported by anyone on the forum in 10 years.

I guess we have beat the topic to death now, but I feel bad that the OP has based his decision on what I know to be faulty data.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: Eddgie]
      #5519401 - 11/14/12 11:31 AM

Quote:


There is no "Inductance" in a splitter. Inductance takes a coil, and these devices do not use coils. They simply have buss bars to distrubute the voltage to the different sockets.





Actually, any conductor (i.e. any wire) has inductance. While a coil has MORE inductance than a straight wire, the wire between the source (battery) and load (mount or heater) can certainly have enough to cause a voltage spike. And if you look a the formula for induced voltage (V=L di/dt), you'll see that it has NOTHING to do with the supply voltage. It's only related to the inductance and the rate of change of the current. Thus, when you have a large current that you're trying to instantaneously make zero (turning it off) it doesn't take much inductance to get a really hefty voltage.

And lest someone wishes to question my credentials as at the start of this thread, I actually have a Ph.D. in Physics, and am Director of Technology Development for the world leader in test equipment for evaluating electromagnetic compatibility (EMC). Thus, this is pretty much the type of stuff I've dealt with on a daily basis for about 25 years! It's pretty easy to get both conducted and radiated interference from unexpected sources. At the same time, there are some simple rules of thumb that will make a lot of difference too. People generally don't realize that there's no such thing as a true "ground" or a perfect conductor, and that the weird rules that electrical codes impose, etc. really do come from somewhere and have reasons to exist.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5519414 - 11/14/12 11:44 AM

Quote:

Hmmm...for some reason the pic didnt come up. I'll try again. I can easily wire in another plug next to the one I already have if the splitter is what he's saying could cause the problem. From what I understand he's saying a 12v battery IS regulated unless something else is plugged into the same socket?





The voltage AT THE BATTERY TERMINALS is going to be pretty constant. But if any loop of wire has an inductance, can anyone see the loop in this picture? The larger the loop, the larger the inductance. One of those rules of thumb I mentioned is that you always try to minimize the size of a wire loop and you NEVER put something metallic/magnetic in between a large loop, especially for AC (that inductive coupling thing that was mentioned previously). To minimize the inductance, your supply wires should come together as quickly as possible and ideally be twisted together. There's more to the idea of a zip cord or a twisted pair than just the convenience of having a single cable vs. separate wires flopping about.

Again, we're generally talking about small contributions and a limited chance of a problem, but accidents do happen. Chances are that a lot of the surges people experience occur when connecting/disconnecting the different components.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5519548 - 11/14/12 01:33 PM

So you're telling me to shorten my hot (white) wire? If I wire in a seperate cig adapter can I use the same battery or does that make no difference?

Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5519571 - 11/14/12 01:50 PM

Just came across this on a web search...."The arcing is usually visible as a small blue arc even in 12 volt systems. It reaches levels that will damage integrated circuits and other components. This damage tends to be 'cumulative' by nature and does not cause immediate failures. Successive exposure eventually leads to component degradation and complete failure."

Post Extras: Print Post   Remind Me!   Notify Moderator  
BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5519575 - 11/14/12 01:56 PM

In the real and ordinary world of automobiles ONE battery powers multiple computerized processor units controlling the engine ,brakes,etc,,also there are power doors and windows, and seats,electrical defrosters,GPS units, stereo radios, and they seem to do pretty well.


One large battery ,good connections, reasonably sized wires, should suffice;and I wouldn't worry.We're NOT dealing with voltages induced by EMP ,lightning, only a couple amps at most.The battery itself is a giant capacitor that will absorb voltage spikes.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: BigC]
      #5519627 - 11/14/12 02:44 PM

Quote:

In the real and ordinary world of automobiles ONE battery powers multiple computerized processor units controlling the engine ,brakes,etc,,also there are power doors and windows, and seats,electrical defrosters,GPS units, stereo radios, and they seem to do pretty well.





Yeah, but do you have any idea just how much testing those systems go through to make that happen? Take a look at this lab's website to get an idea of the number of standards every component gets tested to. I'm sure I'm not the only one who remembers the days of ignition noise on my radio, and that was before there were any other electronics in your car.

Now, while I'm sure that companies like Celestron have to worry about some of the emissions directives (as evidenced by the ferrite core they're now sticking on the end of the hand controller cable as a last-minute fix), I would be very surprised if any of the dew heaters or other after-market components that we all love have ever seen the inside of a lab!

So while many of us (including myself) have never had a problem running mutliple items off the same power supply (AC or battery) that doesn't mean that others haven't or that it can't happen. I'm certainly not going to tell ANYONE that "It'll never happen to you." because it just might, and I don't want to be responsible for the decision that led to their problem. Like anything else, there are precautions that can be taken to minimize the chances of a problem, the most drastic being completely independent supplies. Even there you aren't guaranteed of no problems due to unexpected disconnects, electro-static discharge (ESD), etc.

Heck, one of the coolest catastrophic failures I've ever seen was caused by an ESD on a powered variable speed drive system. A switching power supply was used for the 12V low voltage supply that drove some control electronics for a DC brushless motor. The weird thing on the motor drive was that all of the control circuitry was mid-rail on a ~200V DC supply, meaning that everything had to remain isolated from "ground" to give a +/- 100V supply for the motor. With the unit powered up, a technician was putting the plastic safety cover back on that went behind the power supply board and across all the components, and all of the sudden, every drive transistor on the drive unit blew! It turns out that there was enough static on the plastic cover that it caused an ESD to the back of the 12V power supply. For an instant, there was an ionized path between the isolated supply and the chassis of the case, and the 200V supply shorted right across that, blowing up everything.

BTW, on a related note, I know that the RCA jack on my particular brand of dew heater is wired backwards from anything I would have ever expected. Thus, the outside shell is the +12V, meaning that if it ever comes in contact with my mount when running on the same supply, BOOM! Arcing and blown fuses, and who knows what else. So again, it's just a question of how much of your investment you want to risk.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Eddgie
Postmaster
*****

Reged: 02/01/06

Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5520203 - 11/14/12 09:39 PM

And how much wire would be required to produce an inductance required to triple the input DC voltage?

6000 ft?


Post Extras: Print Post   Remind Me!   Notify Moderator  
bluedandelion
Carpal Tunnel
*****

Reged: 08/17/07

Loc: Hazy Hollow, Western WA
Re: Same battery for mount and dew system? new [Re: Eddgie]
      #5520446 - 11/15/12 01:13 AM

At the risk of saying something unpopular, I should point out that in science credentials matter little. Even Einstein ate humble pie like a good scientist from time to time.

No one has volunteered even anecdotal or hearsay evidence to show that a mount was damaged from being plugged into the same power source as a camera or dew heater. All that was offered was a faint theoretical possibility.

So all this remains is a gaggle of opinions.

Ajay


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: Eddgie]
      #5520547 - 11/15/12 04:23 AM

Quote:

And how much wire would be required to produce an inductance required to triple the input DC voltage?

6000 ft?



How many feet of wire are in the motor of your mount? And what's the di/dt of an open circuit? Zero times infinity is still somewhere in between zero and infinity. The inductance is non-zero and the di/dt is darn high. I'm surprised an EE isn't intimately experienced with the ringing of circuits, which is what we're talking about.


Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Ashfall
member


Reged: 05/28/12

Loc: Pearland, Texas
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5520901 - 11/15/12 10:21 AM

Am I a bad person for powering my CPC directly from my Dewbuster with a custom RCA cable? My CPC doesn't seem to care, it still loves me.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: Ashfall]
      #5521489 - 11/15/12 04:10 PM

Ok, to save my reputation and show that I really DO know what I'm talking about, I did a little experiment. As we like to say in my business, "In God we trust; all others bring data!" So, while I feel like this is an episode of Mythbusters, or that perhaps I should change the title of this post to "Do you believe in MAGIC?!!", since others swear up and down that what I'm about to show is not at all possible, here goes!


Here's the test setup. A three-way cigarette lighter splitter is plugged into the truck accessory port with the engine off (12V battery power only). The oscilloscope is connected to the power cable that would normally run my Meade mount. The cigarette lighter is used to simulate the load of a dew heater, and the oscilloscope is configured to trigger on any voltage rising above about 16 volts.



Here's what happens when the lighter reaches temperature and pops out, breaking the circuit to the "dew heater". There are actually a number of spikes due to the lighter not switching off all at once, but the final disconnect results in a spike of about 37 volts! Note too how the voltage going to the mount is not at the battery voltage to start with due to the load of the heater and the losses in the cable that it's pulling the current through. After the current shuts off and things settle down, it's back to full power.



Here's a zoomed in view of that biggest pulse. Note that if it wasn't for a second harmonic riding on top of the first oscillation, this would have easily exceeded the 40V or more pulse that's been warned of here



It should be noted (in case someone bothers to check) that this splitter came with a "battery protection circuit" that didn't work and wouldn't have done much for the battery if it did. That was removed and the outputs cabled directly, so there's nothing in line with this other than the single zip cord you see. Note that I also ran this same test monitoring directly off the truck auxiliary port with the lighter in the normal lighter port and got pretty much the same result. So much for all the electronics in the vehicle, huh? Thing is, those are DESIGNED to handle the fluctuations caused by this sort of thing, not to mention the noise from an alternator, the ignition, the starter motor, electric windows, power locks, etc. Do you trust that your mount was built to the same standards?

So, feel free to re-run this experiment yourself. It's your choice whether you want to experiment with your expensive scope equipment or not. Myself, I think I'll be re-thinking my own lazy behavior about running multiple equipment off the same supply and see about putting some signal conditioning and suppression in front of my good stuff. I'm not sure I trust that Celestron and Meade did it for me.

And as a final note, remember that this can happen easily with ANY sudden discontinuity in a high current load. I'd suspect that accidentally unplugging your scope while it's slewing is probably as bad or worse than your dew heater flipping on and off.

At any rate, it's up to you who you want to believe. I know what the data shows me, and I always do my best to not mislead people because I THINK I'm an expert. It just so happens in this case I did know what I was talking about. And so did the much maligned Dr. Sharrod.

Happy Viewing!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
bluedandelion
Carpal Tunnel
*****

Reged: 08/17/07

Loc: Hazy Hollow, Western WA
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5521970 - 11/15/12 09:36 PM

Beo,

Now that's great info. Surely we see transients. By the way is the timescale in microseconds?

The question is what damage follows. As Eddgie and others, including me, have pointed out years of use has not resulted in damage.

As you point out the voltage spikes whenever there is a rapid rise in the current (L.di/dt and all that). Now wouldn't that also be the case if one were to simply switch ON a mount? The current goes from 0-2A in a very small time interval. So if transients were to damage mounts wouldn't turning on a mount itself pose a hazard? Most light bulbs blow from the transient when they are turned on.

Now I don't know about specific mount designs. It would seem from the fact that many users are using a setup with multiple inputs and not seeing problems that mount electronics must have some protection built in against these type of transients. That is just an inference. You are better qualified to comment on this than I am.

My own setup has four outputs branching out from an 85 AH wet lead acid battery. These are not scopestuff splitters, but permanent branches made of large gauge cables. I turn on the dew-controller, then my mount, then laptop (plugged in) and finally my imaging gear one by one - not all at the same time. Haven't had any problems.

Meade mount owners who use the DS system have seen some problems. These were not from transients but from power interruptions from voltages running low (brown outs) or the power cable getting accidentally pulled in the middle of a slew. This didn't fry the mount but just garbled the firmware. That is a major headache. I have successfully reset the code in the autostar microcontroller after a cable pull snafu.

So in sum I've not heard of a mount being fried by transients. I am willing to take the risk. To each his own ...

Ajay


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: bluedandelion]
      #5522073 - 11/15/12 10:49 PM

Hi Ajay:

Yes, the highest spike only lasts for a few tenths of microseconds which means that even though there's a pretty good voltage, there's not a lot of energy there. That's still longer than a typical ESD event, although the voltages there can be in the kV range. The full event was about 50 uS, and you can see on some of the earlier peaks that only hit 25V or so, there's considerably more energy involved there (they stay at a higher voltage longer).

I too have used multiple items on one linear power supply (gasp! that's worse than a battery, right?!! ) for quite a while, and although the total number of hours probably aren't huge, I haven't had a failure either. Whether that's because the equipment I'm using is relatively immune, the way I have it set up is relatively safe, or I've just been lucky and the clock is ticking, who knows. The important point is that just because you or I haven't had a failure is not definitive proof that someone else won't, or that the next time you fire up your system something won't go wrong. So telling someone else not to worry about it and there's absolutely no chance of a problem is just irresponsible. It may be that there's a statistically small chance of a problem, but even that's not clear from a handful of users saying "I haven't had a problem."

And no, powering on doesn't cause the same type of spike as powering off does. It's a matter of where the currents and voltages are. When you power on, there is NO current and only the 12V at the battery. The 12V is applied across the resistive, inductive, and capacitive load of the equipment that you're turning on. The voltage has to force the current to start flowing by the inverse of that equation. That is, the rate of change of the current from zero to full current is the voltage applied by the battery divided by the inductance. If the inductance is high, it takes longer to get the current flowing than if it's low. This is also of course an exponential relationship (as were all of the curves I measured) since as more current flows, the voltage differential moves from the battery terminals out to the point where the load is.

That leads to your next point, which is that the closer the split is to the battery, the less likely you are to have a problem. Nice big cables also have lower inductance (as well as lower resistance) than small ones. The closer the split point is to the source, the less likely the stray reactance (combination of C, L, and R) will cause significant voltage differences on the various supply lines.

All of these topics touch on things that are part of good power supply design. All well designed DC electronics should have a nice range of capacitors at their inputs to help mitigate the effect of supply line inductance. When the electronics need a quick source or sink of current, it goes to the capacitors rather than building up voltage trying to force it down the line. Unfortunately I've repeatedly seen engineers (with EE degrees ) forget the most fundamental aspects of power supply decoupling. So who knows what's in the various equipment we're using? Some may be pretty robust, but I suspect most of it (especially the items that are likely to CAUSE the interference) aren't designed or tested to the level of most of your mainstream consumer electronics.

At any rate, as I said early on in this thread, there are some simple rules of thumb that will help minimize the potential of problems, and thus conversely it's possible to have BIG problems if you get things set up poorly or if you aren't careful when you fire up and shut things down. Chances are pretty good that some of the problems reported are due to ESD when people are connecting and disconnecting things in the dry cold air. So regardless of what you do there's always the potential to damage something electronic, especially when it has exposed connections like most mounts do. At the end of the day it's up to each user to decide what they're comfortable with. We just all need to be considerate of our fellow enthusiasts and avoid making unsupported blanket statements about things where they could encounter a very different experience than we've had.

Cheers!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5522540 - 11/16/12 09:55 AM

Well the first thing I would do is rewire the dew heater.

Any exposed socket or plug above or below ground is a disaster waiting to happen.Like the "connector cable " consisting of two male AC plugs for emergency power hookup-a BAD idea that is VERY dangerous.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: BigC]
      #5522577 - 11/16/12 10:15 AM

Very interesting stuff Beo. Thanks for taking the time to perform the test.

Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5524470 - 11/17/12 02:27 PM

That's it - I've taken myself completely off the grid. I don't even know how I'm typing this!

But, seriously, great stuff. I'm in sunny SoCal, so haven't been using dew heaters, but I am interested in an order/procedure for turning OFF the equipment (if that could cause spikes). Also, I'm running my mount, CCD, focuser and USB hub (when I bother to power it) off of one battery (an 80ah LiFePO4) and my laptop off of another battery (20ah LiFePO4). I don't use a cigarette lighter splitter, but Anderson PowerPole connectors/splitter and inline fuses.

So, any particular order to turning things off, and when I do, should I unplug them from the splitter before turning the next one off? Hey, if it's simple, better to be safe than sorry, and if it's difficult...screw it.

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5524637 - 11/17/12 04:23 PM

Interesting experiment, but, and I say this knowing nothing about this kind of thing, does the fact that the truck's battery is not isolated from the other systems, like ignition, alternator, ect (things that do put out high voltage to run the engine) cause a role in creating the voltage spike? Just wondering if this a valid experiment for the actual situation we are trying to replicate?

Post Extras: Print Post   Remind Me!   Notify Moderator  
BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5525122 - 11/17/12 09:16 PM

You seem to be doing things correct;Anderson Powerpole are much better than a mish-mash of "convenient" gigarette lighte plugs.Good solid connections prevent a lot of problems.

There are Transient Suppression Devices sold by a number of electronic suppliers including LittleFuse. Might be something to investigate.


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: BigC]
      #5525139 - 11/17/12 09:28 PM

BigC - never heard of them (no surprise there). Went to LittleFuse, but couldn't figure out what I would need. As much science in my background as I had, Electrical Engineering was never one of them. E&M, yes, practical stuff...not a clue. What would I use for a 12V DC unit with batteries, and where would I put them in line? Also, do they suck up juice, or are they passive? Like I said: if it's easy, I'll do it. I'll give LittleFuse a call on Monday and see what they say.

Thanks,

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
ericsolo
member


Reged: 12/27/05

Loc: Edmonton, AB, Canada
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5526593 - 11/18/12 06:37 PM

What about using a Kendrick powerpack?
http://www.kendrickastro.com/astro/battery.html
I have wondered if these would provide sufficient protection to prevent damage to equipment...

Eric


Post Extras: Print Post   Remind Me!   Notify Moderator  
salientbunny
member


Reged: 06/13/12

Loc: Southeast Georgia, US
Re: Same battery for mount and dew system? new [Re: ericsolo]
      #5526687 - 11/18/12 07:35 PM

http://www.translectricinc.com/catalog/partdetail.aspx?partno=SM480-8

Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: salientbunny]
      #5526779 - 11/18/12 08:24 PM

Dude! That's perfect...I think (since I don't know enough about this). One for the mount, one for the CCD camera, one for the Lodestar, and screw the focuser (or maybe I'll get one for the focuser).

It's low DC impedance, too, so it shouldn't suck up much of anything to put a hit on my battery.

Thanks!

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: mgwhittle]
      #5526837 - 11/18/12 08:57 PM

Quote:

Interesting experiment, but, and I say this knowing nothing about this kind of thing, does the fact that the truck's battery is not isolated from the other systems, like ignition, alternator, ect (things that do put out high voltage to run the engine) cause a role in creating the voltage spike? Just wondering if this a valid experiment for the actual situation we are trying to replicate?




I was counting how long it would take before someone suggested I did something wrong. Again, anyone else is welcome to do their own experiments and share the results, or feel free to contact Adam and Jamie and see if they'll do a show on the topic, but since I'm not MythBusters I don't have to do a re-visit show! The physics said this was what would happen, but people complained "that's just theory." The experiment SHOWS it happening, and still there must be something wrong. If someone doesn't want to believe that surges and spikes are a possibility, that's their choice and I'm not going to waste any more time trying to convince them. I've seen enough to make me at least pay a bit more attention to the way I configure things, and it will definitely impact the way I set up my power supplies in my observatory.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: salientbunny]
      #5526866 - 11/18/12 09:11 PM

Quote:

http://www.translectricinc.com/catalog/partdetail.aspx?partno=SM480-8




Interesting solution although a bit pricey. Still, an ounce of prevention... To convert some of techno-babble on the spec sheet: 3dB at 60 Hz only drops the voltage by 30%. 12 dB at 600 Hz drops it about 75%. Since the spike I generated (and anything you'd expect including ESD) was in the MHz region, I'd assume it has much better clamping than that shown. Wish they'd actually SHOW the full frequency response though!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5526892 - 11/18/12 09:25 PM

Quote:


So, any particular order to turning things off, and when I do, should I unplug them from the splitter before turning the next one off? Hey, if it's simple, better to be safe than sorry, and if it's difficult...screw it.





Splitting the power at the source is still the best solution for minimizing the problem. Don't run a long cord and then split it. For those who've had the experience, this is much like the situation where turning on a big power tool on the same circuit or extension cord as a light will dim the light, and yet not dim a neighbor's light or usually even one on a separate circuit. Just like the resistance and inductance of that circuit causes the light on the same circuit to dim, so the inductance of that circuit will also cause a surge with the current draw stops. But if you're on a completely different branch, then the surge that occurs on one leg will have minimal impact on the other.

Beyond that, presumably it's better to turn off the lower current draw and more sensitive electronics first, then the heavy stuff. However, since your dew heater is probably flipping on and off constantly, you still have the potential for the problem just in operation. And frankly, accidentally pulling the power in the middle of a fast slew on your scope is probably one of the worst things that could happen (and does regularly since that's the most likely time for the cord to come unplugged!). Since the motor should be protected for back EMF at the drive transistors, it's probably ok for the drive itself, but other things that were plugged in with it may get a bit of a jolt.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5526927 - 11/18/12 09:53 PM

Beo - found those suckers for $16 a pop, so I'm gonna get three. I figure they're less than 1% of the cost of each piece of gear they're protecting, so that's worth it to me. Coupled with my splitter being right at the battery (after an inline fuse) and I don't run dew heaters...yet. And all of it still cheaper than the Kendrick stuff (which I like very much and almost got, but they're less flexible than this: PowerPoles are like Legos).

I was going to put my splitter up on the scope to minimize cords, but now I won't (though the USB hub's goin' up there).

Hopefully I'll never know if I need them.

Even though I'm a hitchhiker on this thread, I appreciate the input everyone's had.

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5526930 - 11/18/12 09:55 PM

Quote:

Quote:

Interesting experiment, but, and I say this knowing nothing about this kind of thing, does the fact that the truck's battery is not isolated from the other systems, like ignition, alternator, ect (things that do put out high voltage to run the engine) cause a role in creating the voltage spike? Just wondering if this a valid experiment for the actual situation we are trying to replicate?




I was counting how long it would take before someone suggested I did something wrong. Again, anyone else is welcome to do their own experiments and share the results, or feel free to contact Adam and Jamie and see if they'll do a show on the topic, but since I'm not MythBusters I don't have to do a re-visit show! The physics said this was what would happen, but people complained "that's just theory." The experiment SHOWS it happening, and still there must be something wrong. If someone doesn't want to believe that surges and spikes are a possibility, that's their choice and I'm not going to waste any more time trying to convince them. I've seen enough to make me at least pay a bit more attention to the way I configure things, and it will definitely impact the way I set up my power supplies in my observatory.

Beo




Whoa! Hey Beo, I never said you did something wrong. As I pointed out, I have no knowledge of these things electrical. I read with interest your experiment and appreciate the hard work. My question about the electronics/electrical components and what affects they might have was because I myself don't know the answer. I didn't mean to imply that you did anything wrong, I just was curious about that variable.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: mgwhittle]
      #5527148 - 11/19/12 12:28 AM

Hey Mark,

No problem. The only thing having a factor here is the amount of wire between the battery and the load, in this case the cigarette lighter. You can figure that the distance from the battery to the outlet on the dash is probably no more than six or eight feet. At least half of that path (the body of the truck) is a relatively low impedance path too.

Note too that this was also addressing the one comment about car electronics not having a problem, so it must be ok. The car electronics are designed to handle things like the surge caused by a cigarette lighter kicking off, but the surge is still there!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5527179 - 11/19/12 12:49 AM

Thanks Beo, that clears it up for me. I guess I should have realized that all the other wiring in the car really doesn't matter because you have power at the cigarette lighter without having the ignition on, so it not like its going through some complicated route to get there. Just like you pointed out, from the battery to the dash. Good job on demonstrating this!

Post Extras: Print Post   Remind Me!   Notify Moderator  
bluedandelion
Carpal Tunnel
*****

Reged: 08/17/07

Loc: Hazy Hollow, Western WA
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5527252 - 11/19/12 01:47 AM

Quote:

The physics said this was what would happen, but people complained "that's just theory."




What most people said was that mounts don't seem to be hurt despite years of usage even though there are transients.

Ajay


Post Extras: Print Post   Remind Me!   Notify Moderator  
Michael2
member


Reged: 06/01/11

Loc: Australia
Re: Same battery for mount and dew system? new [Re: bluedandelion]
      #5528543 - 11/19/12 06:35 PM

Beo, thanks for going to the trouble of setting up the experiment and the detailed explanation.
I have noticed for a while, that people just seem to accept Hand Controller failures as inevitable/old age or whatever. Maybe armed with this extra information and a little more care in setup procedures longevity might increase.
Thanks also to the Original poster for starting this thread.
Michael
Australia.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: Michael2]
      #5528605 - 11/19/12 07:13 PM

Quote:

Beo, thanks for going to the trouble of setting up the experiment and the detailed explanation.
I have noticed for a while, that people just seem to accept Hand Controller failures as inevitable/old age or whatever. Maybe armed with this extra information and a little more care in setup procedures longevity might increase.
Thanks also to the Original poster for starting this thread.
Michael
Australia.




You are very welcome and a big thanks goes out to Beo. If nothing else some people might get a few more years of service out of their equipment....even if they dont know it, but thats the best part!


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: rflinn68]
      #5528642 - 11/19/12 07:31 PM

Yup, thanks from me, too. Who knows if it'll help...but it couldn't hurt!

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5531278 - 11/20/12 11:11 PM

Thanks all. This was a fun exercise. And no offense or hard feelings to any of those who've expressed differing opinions. It's just that while you might argue with the physicist, you can't argue with the physics! It's like gravity; it's not just a good idea, it's the law!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
n1wvet
super member
*****

Reged: 04/22/11

Loc: Northern Virginia, USA, Earth
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5531442 - 11/21/12 01:44 AM

There is no arguing with the di/dt physics and the resultant transients. But your results show an open circuit (ignoring the load of the 'scope). The dew buster and mount present very different loads and may make the transients lower or higher. I have been running my laptop, mount and dewbuster off of the same bettery with no observable problems so far for several years now. The only way to detect a problem would be to measure the exact setup under varying conditions (temp, slewing, heating, etc.) The test data is excellent example of di/dt but not necessarily what's relly happening. There are many variables to take into account.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Arizona-Ken
Pooh-Bah


Reged: 08/31/08

Loc: Scottsdale, Arizona
Re: Same battery for mount and dew system? new [Re: n1wvet]
      #5531730 - 11/21/12 08:59 AM

Yes physics is physics, but the application of physics is the rub. That's where the engineers come in.

There was really no circuit analysis of the drive electronics, nor the dew controller electronics, just statements that they are probably not properly designed for voltage spikes. There was a basic total discount of the fact there is no reporting of drive electronics failures associated with dew controllers powered from the same battery.

Being "safe" without detailed analysis can lead to separate batteries for everything - hey - why not one for the telescope drive, another for the dew system, another for the computer, another for the camera, etc? You would definitely be safe, but you would be wasting your money.

I understand Beo's physics and oscilloscope screens, but disagree with his conclusions. Not arguing with physics, but arguing about incomplete analysis.

Oh yeah, by way of disclosure, I am one of those darn electrical engineers....

Arizona Ken


Post Extras: Print Post   Remind Me!   Notify Moderator  
RGWOOD
member


Reged: 05/17/10

Loc: Lake Jackson, Tx
Re: Same battery for mount and dew system? new [Re: Arizona-Ken]
      #5531804 - 11/21/12 09:43 AM

Being an engineer myself, I cannot help but wade in on the discussion. The experiment that Beo did showed that it is at a minimum possible to get these transient spikes on the line. Everyone's setup may be quite different and so it would be difficult to duplicate exactly.
My take always from the discussion are a) try to have a dedicated power source for the scope, and b) if you must use the same battery, avoid splitters and tie in each device directly to the battery posts to minimize the transients.

Thanks Beo for the refresher in electronics 101.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Same battery for mount and dew system? new [Re: RGWOOD]
      #5531830 - 11/21/12 09:58 AM

Nobody said it will instantly take out a brand new mount. The spikes are there and do happen and it is an accumulated failure that wears on the electronics over time and it will eventually take out a mount. Batteries and power sources are cheap so it is not "wasting your money". But now it is up to everyone to make their own decisions on how to care for their equipment. I simply raised the question and have decided now what I will do. I will not be taking any chances, cant afford to. Its a little inconvienent but whats one more battery, especially when I already have one.

Thanks to all who offered up their opinions and shared their experiences. And a big thanks the Beo for taking the time to varify these claims. Much appreciation to all


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: Arizona-Ken]
      #5531917 - 11/21/12 10:42 AM

Again, feel free to repeat these experiments on your own mount and other equipment. I'm not going to do so. And yes, what the voltage spike looks like to the mount or anything else depends on what the load itself looks like. I've already indicated that a properly designed power supply circuit, with appropriately rated capacitors, etc. will handle these sorts of transients. On the other hand, there's a reason that there is a huge market for surge suppression products. These aren't just about protecting from lightning strikes, but also about protecting products from each other. The fact that one might go the life of a product without it ever dying due to surges does not discount the fact that many people DO have product failures due to surges whether they know that's the cause or not. It also does not change the fact that these effects are cumulative, and that a failure may occur at a point where no significant cause is apparent. This same cumulative effect is seen on the surge suppression devices themselves. Eventually they fail and have to be replaced, whether you've ever seen a spike that exceeds their ratings or not.

So, to our own hobby, unless you're telling me that no one has ever had a product failure, then there is evidence that devices fail, whether or not we know the causes of the failure. There are certainly also people who warn against indiscriminately combining different loads due to the potential for a problem, and I don't believe they're all just paranoid. Just because they aren't here saying "I can prove my mount failed due to..." doesn't mean they don't exist.

Now, to my analysis:

Claim 1: "There is no way to get a 40 volt spike out of a 12 volt battery." - Disproven

Claim 2: "You are not ever ever ever going to get a 40 volt spike out of a 12 volt battery." - Ok, so I only produced 37V, but it's obvious that more or less is possible.

Claim 3: "There is no "Inductance" in a splitter. Inductance takes a coil, and these devices do not use coils." - Obvious nonsense. Any conductor has inductance. The spikes produced wouldn't have happened without it.

Claim 4: "And inductance by itself will not cause a spike that is bigger than the voltage put into it." - Disproved. Both the equations and experiment show that the voltage of the battery have nothing to do with the voltage of the spike.

Claim 5: "Anyone that has a formal education in electronics engineering would tell you that you can't get a 40 volt peak from a 12 volt battery/splitter combination." - Well, I have a formal education and I'm here to say you can and I did (well, 37V, but I didn't want to spend the time futzing with it to get that perfect trace!)

I'm sure there were more claims I was disproving, but you get the idea. Read through my posts and show me where I ever said that "if you do this you're guaranteed to blow up your mount." What I've said is that there is the POTENTIAL for a problem, although that potential may be less than that for damage from ESD due to the user touching the wrong thing without discharging, but that potential can also be mitigated by following a few simple rules or taking extra precautions. That's what branch circuits and surge suppressors are about in your house. They're all safety precautions to minimize the potential of a problem. What I've also said is that it's irresponsible of us as a community to tell anyone, especially a novice that "There's absolutely no way you'll ever have a problem." Present the REAL facts and let them make their own decisions.

And as a final note on electromagnetic compatibility (EMC) as a whole. Only Europe requires that devices be tested for whether or not they're susceptible for interference, and chances are that most of your telescope equipment manages to dodge the consumer electronics clauses, especially since the mount is on a 12V supply. Is there a CE mark on your dew heater or scope? The power supply (from a third party manufacturer) may have one, but I can tell you there's not one in the CGEM manual, nor any certification of conformance to that or FCC requirements. FCC does require testing to ensure that electronics don't cause interference (conducted or radiated) to radio, etc. so is there any sort of FCC Part 15 notice coming with your dew heater? Having dealt with manufacturers of all sizes, I can tell you that most view EMC only as a cost center and a regulatory evil. Few will add components to mitigate problems (or potential problems) unless testing proves they absolutely have to. (And lest someone says, "But they've tested and shown it wasn't a problem.", the manufacturer defines the typical scenario, so if the typical scenario is the device on its own battery, what does that prove in this case?) And the smaller the company (e.g. the less noticeable to FCC, etc.) the more likely they are to at most self certify (usually without any testing), or more likely just do nothing at all, and hope they never have a problem with the FCC. (And lest someone say I'm generalizing and they work for a small company that is diligent in their EMC certification, that's not what I'm saying! I've seen extremely LARGE companies (you'd be surprised) who didn't do any real EMC until they got their hands slapped big time!)

So, it's still up to each individual to make their own decision, but there is the POTENTIAL for interactions between devices that could cause failures, and they aren't all surges. Power dips can be deadly too. There are also ways to minimize those chances. The value of an ounce of prevention over a pound of cure is also up to the individual. Some people carry insurance on their equipment and many don't. Same choices. However, if you're relying on the assumption that the various component manufacturers "know what they're doing" or that they've tested your particular combination to guarantee there are no problems, then you're probably deluding yourself. And given that I saw at least one post here saying a manufacturer recommended running their mount on its own supply, to which at least one response indicated they were just trying to protect there warranty... Well, you do what you want, and I'll do what I want, and best of luck to all of us!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
wiruna
member


Reged: 08/11/06

Loc: Sydney, Australia
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5534261 - 11/22/12 05:48 PM

Quote:


So, to our own hobby, unless you're telling me that no one has ever had a product failure, then there is evidence that devices fail, whether or not we know the causes of the failure.

Beo



Well said. Ive had motors on my Losmandy G8 fail. Why? Who knows? But at the time I was running everything off the same battery.


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: wiruna]
      #5534646 - 11/22/12 11:49 PM

So, thanks again to salientbunny: got the noise/spike filters (3) for $16 each - am now putting PowerPoles on them. There is a particular direction: battery, to filter to electronic component. I'm going to put them after the splitter, if I read what everyone's said correctly, so if a spike did come down the line from another piece of equipment (like, my...say, nonexistent at the moment dew heaters, it would then come from the "battery" side through the splitter and be filtered by these suckers).

Will take a picture when I get it all done. An ounce of prevention is worth a stitch in time...or something like that.

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5536242 - 11/23/12 08:50 PM Attachment (15 downloads)

Here's a quick bad shot. The black boxes (not fixed to the battery box yet) are the spike filters. The PowerPole splitter is in front. There's a cigarette lighter plug for emergencies (someone's battery at a star party dies, etc.) and for testing out new gear before PowerPole-ing it.

So far, so good,

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5536436 - 11/23/12 11:19 PM

Looking good!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
n1wvet
super member
*****

Reged: 04/22/11

Loc: Northern Virginia, USA, Earth
Re: Same battery for mount and dew system? new [Re: Lord Beowulf]
      #5536590 - 11/24/12 02:15 AM

Hi psandelle, maybe I missed it - could you post info on the filters? I my add a set of these to my rig as well. Also, the Power Poles work well. (looks like we used the same size) The power poles provide good peace of mind that I can't plug thinks in backwards in the dark. They only go together one way, red to red, blk to blk.

Post Extras: Print Post   Remind Me!   Notify Moderator  
MikeML
professor emeritus
*****

Reged: 10/09/04

Loc: NJ
Re: Same battery for mount and dew system? new [Re: n1wvet]
      #5536747 - 11/24/12 07:57 AM

No discussion on ground loops? Only way to be sure is to isolate the DC supply. That said, never had a problem with the dew controller.

Edited by MikeML (11/24/12 07:58 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: MikeML]
      #5537104 - 11/24/12 11:41 AM

Courtesy of salientbunny above:
http://www.translectricinc.com/catalog/partdetail.aspx?partno=SM480-8

I got them for $16 at auction (some still there, probably). PowerPoles are like Legos, and I can change rigs and wiring with ease. Great contacts, too, so I never worry about sporadic power. Also, "almost" everything takes a 2.1mm, or 2.5mm plug, so I can build power connectors easily.

Mike: okay, tell me about ground loops and what I can do about them...sigh. Next, I'll get a lightning rod and then build a house around it, and then build an observatory, and then plug into the wall.....

By the way, I'm sure there are lots of places to get PowerPoles, but the PowerWerx company are very helpful - great people, and send it out quickly.

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
MikeML
professor emeritus
*****

Reged: 10/09/04

Loc: NJ
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5537264 - 11/24/12 01:43 PM

Paul:
http://s.eeweb.com/articles/2012/02/20/ground-loops-1329780807.pdf
The easiest way to avoid them is run everything through it's own power supply whether it's own battery or AC to DC converter.


Post Extras: Print Post   Remind Me!   Notify Moderator  
HunterofPhotons
Pooh-Bah


Reged: 04/26/08

Loc: Rhode Island, USA
Re: Same battery for mount and dew system? new [Re: MikeML]
      #5537361 - 11/24/12 03:04 PM

Quote:

...The easiest way to avoid them is run everything through it's own power supply whether it's own battery or AC to DC converter.




I'm not sure what you're trying to say, but the way to avoid ground loops is that everything, especially your sensitive equipment, should share a common ground. Differing grounds of differing potentials are the source of ground loops.
Dew systems with their constant heavy switching are usually put on a different power supply to avoid interference.

dan k.


Post Extras: Print Post   Remind Me!   Notify Moderator  
orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Same battery for mount and dew system? new [Re: MikeML]
      #5537369 - 11/24/12 03:12 PM

Everybody is safe, I use 1 battery for both, so if there is one failure per 1000 people, MINE will Fail, so you are all good to go.
Insurance companys lock their doors when they see me coming,
When I call, as soon as they hear my voice I hear,
" No Habla English"
People on Suicide watch hang around me.
You can tell it is me coming, by the Black Cloud hovering above my head, and the burn marks on my Hat and shoes from the lightning strikes.


Post Extras: Print Post   Remind Me!   Notify Moderator  
psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: Same battery for mount and dew system? new [Re: orion61]
      #5537406 - 11/24/12 03:39 PM

So, should these noise filters I have help with the ground loop problem? If not, what do I put where?

orion61 - thanks, man! I appreciate that. It's good to have a super power. Mine is: any line I get into will become the slowest line. I have data culled over decades. One line could have a hundred people, and mine will have one, my teller/cashier will have a fit and 911 will be called. Never fails.

Paul


Post Extras: Print Post   Remind Me!   Notify Moderator  
MikeML
professor emeritus
*****

Reged: 10/09/04

Loc: NJ
Re: Same battery for mount and dew system? new [Re: HunterofPhotons]
      #5537414 - 11/24/12 03:43 PM

Quote:


Differing grounds of differing potentials are the source of ground loops.

dan k.




Yes they are.
The common ground or neutral is the path for the ground loop.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pauls72
professor emeritus
*****

Reged: 10/28/07

Loc: LaPorte, IN
Re: Same battery for mount and dew system? new [Re: orion61]
      #5537543 - 11/24/12 05:05 PM

Cigarette lighter adapters and splitters are notoriously poor quality connections. You are better using either ring or spade connectors or other types of sockets/plugs. The second problem with the Cigarette lighter splitters is that the wire from the plug to the splitter is usually a fairly small gauge and not up to carrying a lot of current. Which means you will have voltage drop across the wire and maybe a potential fire hazard if the wire gets hot.

My background is in electronics and I use one battery to power my Atlas mount, dew heaters, and my SBIG camera all at the same time. A large auto/marine type battery is a great filter in itself. As long as you use heavy enough gauge wire and connectors back to the battery you should be OK. You just need to stop before the battery voltage gets too low to prevent damage to the battery.

Lord Beowulf's test while looking impressive really isn't. That 37V pulse looks to be only 100 nano seconds wide (0.0000001 seconds). That can easily be taken care of by a by a small filter capacitor. Yes, your mount, camera and most electronics and at least a minimal amount of power filtering. Sorry I don't have have a digital storage scope, only an old analog one, so I have no way of capturing screen shots of short events. But if Lord Beowulf puts his oscilloscope across the terminals right on the battery and re-performs the test the pulse will only be a small fraction of the amplitude that it is in his experimenter.

You are probably way more likely to blow something up with electronics in it (including your mount or hand controller) from static in your house during winter. A static discharged is in the thousands of volts. It takes about 25K Volts to jump 1 inch, so even the 1/4 inch spark around 6K Volts.

If you are paranoid you can buy or build a filter assembly for each device. But first I would chuck out all the cigarette lighter adapters.


Post Extras: Print Post   Remind Me!   Notify Moderator  
thesubwaypusher
scholastic sledgehammer
*****

Reged: 07/08/04

Loc: New York City
Re: Same battery for mount and dew system? new [Re: Eddgie]
      #5537987 - 11/24/12 10:40 PM

Well, I don't know what Dr. Clay is a doctor of, but my guess is that it is not Electronic Engineering.

So dude, if Dr Clay scared you, I am sorry to hear that, but my experiecne and my electronic background both say that this myth is busted.

I do not know what DR. Clay is a doctor of, but as an electronics engineer, I would say that however he came by this position, it is in error.

And how much wire would be required to produce an inductance required to triple the input DC voltage?

6000 ft?



You're just too funny.


Post Extras: Print Post   Remind Me!   Notify Moderator  
n1wvet
super member
*****

Reged: 04/22/11

Loc: Northern Virginia, USA, Earth
Re: Same battery for mount and dew system? new [Re: psandelle]
      #5538193 - 11/25/12 02:00 AM

Thanks Paul, agree on the interchangability. I use Power Poles on both batteries, both scopes, kybd lighting (red) and dew controller. Everything is compatible.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pauls72
professor emeritus
*****

Reged: 10/28/07

Loc: LaPorte, IN
Re: Same battery for mount and dew system? new [Re: thesubwaypusher]
      #5538198 - 11/25/12 02:02 AM

Dew Controller, I had it hooked up my 14amp hour battery with 2 dew straps output port 1 11"-9 ohm;, port 2 2"-48 ohm; and ports 3 and 4 using 1K ohm; load resisters. I changed my dew controller program to switch all 4 outputs on/off together at 80% duty cycle.




Basic Schematic of the dew controller.




Point #1, About an 11V swing as this is the on/off to the dew strap it is expected. Scope is set to 2 Volts/CM and zero volts is set to the bottom line. Yes, I know the trace on my scope is slightly crooked.




Point #2 This if the 12V buss/supply to the output ports (dew straps) right at the connectors. There is less the 1/2 volt ripple at this point.




Point #3, this is the 12V input to the dew controller. It is flat line DC.



Post Extras: Print Post   Remind Me!   Notify Moderator  
teskridg
Pooh-Bah


Reged: 01/15/08

Loc: PA
Re: Same battery for mount and dew system? new [Re: jrbarnett]
      #5582950 - 12/21/12 06:03 PM

"My observing philosophy: Find out what it is that your telescope doesn't do well, then don't do those things."

Jim: this may be the smartest single sentence I've read on these fora. Thank you! Tim


Post Extras: Print Post   Remind Me!   Notify Moderator  
Ronnie Miller
member
*****

Reged: 12/19/10

Re: Same battery for mount and dew system? new [Re: teskridg]
      #5591187 - 12/27/12 01:11 PM

Can someone tell me how these filters will stop the voltage spikes? The filter input range is from 4 to 60 volts and if the spikes are around 40 volts, would it not let them pass through to your equipment? Or does is suppress anything other than the nominal input voltage applied at the source?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pauls72
professor emeritus
*****

Reged: 10/28/07

Loc: LaPorte, IN
Re: Same battery for mount and dew system? new [Re: Ronnie Miller]
      #5591256 - 12/27/12 02:08 PM Attachment (5 downloads)

The simplest explication is to think of filters as surge suppressors.
Voltage spikes are of a very short duration, so this effectively makes them a very high frequency pulse and makes them very easy to get rid of. The energy from the voltage spike can either be dumped to ground or averaged out over a long period of time depending on the design of the filter.

You will end up with something like this:


Edited by Pauls72 (12/27/12 02:40 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | (show all)


Extra information
4 registered and 24 anonymous users are browsing this forum.

Moderator:  Cotts, Starman27, kkokkolis 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 4363

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics