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Equipment Discussions >> Cats & Casses

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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.


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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


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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!

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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


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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.


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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!


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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


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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


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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.

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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


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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.


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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


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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


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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.


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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


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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


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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


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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.

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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)


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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


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