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Equipment Discussions >> Mounts

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Pauls72
professor emeritus
*****

Reged: 10/28/07

Loc: LaPorte, IN
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Cliff Hipsher]
      #6123158 - 10/07/13 05:28 PM

Most of Europe uses 230VAC 50HZ. They use power receptacle's that are 2 hots with a ground pin. The ground pin should be tied to a water pipe or copper rod driven into the ground no matter what country you live in or what type of power they have.

Many power supplies now days are auto ranging, so they don't care if you plug them into 120V or 240V or any place in between. The only thing that is different is the plug on the line cord that you plug into the wall receptacle. So this same problem exists in other countries too. The big difference is that with a 230VAC input you most likely would have a higher voltage on the chasis.

The concept of "double insulation" is good electrical design practice.

I can tell you for sure that with the chassis tied to 0V, this mount would not have received UL approval if submitted for testing. (Underwriters Laboratories an organization here in North America that Certifies products as to their safety. It is an optional Certification.)


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Jack Huerkamp
Vendor - Waning Moon


Reged: 10/13/05

Loc: Louisiana
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Mike X.]
      #6123258 - 10/07/13 06:01 PM

I didn't have a voltmeter with me at ECVAR. I will run tests when I get home

Jack Huerkamp


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Jack Huerkamp
Vendor - Waning Moon


Reged: 10/13/05

Loc: Louisiana
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Pauls72]
      #6123264 - 10/07/13 06:03 PM

So far I have only been using a 12 VDC marine deep cycle battery to power my AZ-EQ6. I will have to run the test with an AC power supply.

Jack Huerkamp


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qsipiMcKenna
member


Reged: 06/29/13

Loc: MK, UK.
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Mike X.]
      #6123298 - 10/07/13 06:16 PM

Hi Mike.
I have a MON2, (Russian I think), and I now have a CGEM. Both exhibit the same electrical tingling that you describe. The only solution I found was to make a clip that attaches to a tripod leg and run a wire from it to a metal stake driven into the ground below the tripod.
I will be very interested to hear what skywatcher say when your importer gets a reply.
Clear skies, Tony.


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HowardK
Pooh-Bah
*****

Reged: 10/20/10

Re: AZEQ6GT tripod gives me electricity tingle new [Re: qsipiMcKenna]
      #6123308 - 10/07/13 06:22 PM

There is no ac/dc power supply for the azeq6.
Only a cigar lighter type plug.

How comes the OP is powering up with ac/dc power?

Please explain?


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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: AZEQ6GT tripod gives me electricity tingle new [Re: HowardK]
      #6123322 - 10/07/13 06:29 PM

Hello guys, thank you all again for the comments.
Byrne, thank for the feedback on the Cgem!!
Howard , it is easy, I bought a female cigar lighter and a female power plug for the wallmart adapter, a small cable and I soldered it.
For the variable linear power supply on the other hand things are even simpler, all you need is a cable that attaches on the negative and positive output poles of the supply. I will upload a photo ASAP so you can see it, it is simpler that way.

Jack , can't wait to read your test too! thank you!

Edited by Mike X. (10/07/13 06:30 PM)


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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Mike X.]
      #6123381 - 10/07/13 07:08 PM

Here is a photo of the adapter i made.
It gives two alternatives for connecting the mount on a power source.

1)A standart female power plug that comes with most wall mart power supplies
1)2 cables for attaching them a) on a battery or b) on a laboratory power supply.

On the other side there is a female cigarette power plug that connects to the cable supplied by Skywatcher.


Edited by Mike X. (10/07/13 07:10 PM)


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T1R2
Pooh-Bah


Reged: 06/11/13

Loc: NeverWhere
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Mike X.]
      #6123615 - 10/07/13 09:08 PM

If the masking tape is a place where there is a splice, if it touches any part of the mount or legs when hanging down then the current could go through, if this is the case I'd use electrical tape,

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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: AZEQ6GT tripod gives me electricity tingle new [Re: T1R2]
      #6123636 - 10/07/13 09:21 PM

Hello T1R2, thank you for the comment! tYou are right,he masking tape is there for keeping the cable together only.
When it is not used it is isolated with electric tape.
At the moment i am using those two cables for attaching the adapter on a lab.power supply and i had to take it off for taking the photo


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ErikB
super member


Reged: 02/05/06

Loc: Central Arizona
Re: AZEQ6GT tripod gives me electricity tingle new [Re: Mike X.]
      #6123914 - 10/08/13 12:20 AM

Mike, there are two approaches to electrical safety in a case like this. As has already been pointed out, double insulation is one, and it is particularly good in cases where you are going to be outdoors or otherwise near moisture. The other approach is to have everything including the actual device grounded (as you have found). Both systems are designed to guard against a single failure such as isolation breakdown causing the user to be connected to a voltage and current that are high enough to be dangerous. In the case of double insulation, the extra safety is lost only if one of the insulation instances within the device is broken, an unlikely occurrence unless there is visible physical damage. In the case of the system that relies on grounding, the user can lose the extra protection easily, simply by employing an a/c adapter or cord that lacks a ground connection, either by design or by (possibly invisible) damage. All that is about moving the real danger closer, from two steps away to a single step away. It sounds like your equipment is of the kind that uses grounding.

However, it is a common occurrence to be able to feel a tingle in situations where there is no direct danger (but you have lost the extra level of protection afforded by grounding). A designer of a power supply will often want to reduce the possibility that radio signals picked up by the huge antenna that is the power grid will get into the powered equipment. Failure to to this may lead to a nearby transmitter causing the powered device to malfunction. Did you ever hear the neighbor's CB transmitter in your stereo? Transients caused by switching and lightning can also cause problems. In microprocessor-based equipment, just one transient may be enough to reset the firmware, or cause it to act erratically. So how does the power supply designer prevent transients and radio signals from getting in? Well, there are elaborate filters and simple ones. About the simplest is a small capacitor across the power line, and more advanced designs also commonly contain such capacitors. It is very common to use two small capacitors, one from the hot power wire to the protective ground, and another from the neutral power wire to protective ground (since both are different from the protective ground, and both can carry radio frequencies and transients). These are small capacitors that have high reactance, and they are not capable of carrying a dangerous current (but failure in one of them would be dangerous).

What do these capacitors have to do with the tingle? Since the system relies on grounding, it is likely to be designed to carry the protective ground all the way from the power outlet to the metal chassis of the powered device. If the DC power cord doesn't carry the protective ground in a separate wire, but uses just 2 wires, as is commonly the case with telescopes etc, then one of these wires will be connected to the protective ground. Usually this is the negative wire, and this is often connected to the chassis of the device (in this case the mount). But that wire is also connected to the midpoint of the two capacitors, so that it can carry to protective ground to your device. Assuming the two a/c power wires consist of one hot wire and one more or less "cold" wire, the point where the two capacitors come together acts as a high impedance (low current) source of about half the a/c voltage, and this is connected to your device (mount) chassis. Through this mechanism you can under certain circumstances measure a dangerous level of voltage on your device without having a risk of dangerous current, and without dangerous current you can't be hurt.

Now the protective ground from the power outlet is supposed to short out that small current to ground. If you do feel the tingle, it may be because that protective ground is broken somewhere. Assuming your a/c power cord has a separate protective ground wire, it might be broken. Or the power plug might be a 2-prong type that lacks the ground pin. Or you might be using some kind of adapter that lacks ground connection. Or your wall outlet may lack a ground connection, or the ground wire in the wall may not be connected properly to ground or to the outlet. One thing you can try is to check with a continuity tester (ohm meter on low range) whether you have a connection all the way from the mount chassis to the ground pin of the a/c power plug. You may be able to purchase a tester that plugs into the wall outlet to verify that the outlet is properly grounded.

The above represents some general information about common situations, and I don't know enough about your equipment to say if it is applicable. However, let me mention one very special situation that I have encountered. Once I was running telescope equipment in the field with a power supply made for a/c power, and my actual power source was a 12V battery (not the right DC voltage for my equipment though). So I used an inverter to get from 12V DC to a/c, and then from there to the DC voltage my equipment wanted. Then I found out that the inverter had some rather unusual requirements with regard to grounding vs non-grounding. But that is another story.


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HowardK
Pooh-Bah
*****

Reged: 10/20/10

Re: AZEQ6GT tripod gives me electricity tingle [Re: ErikB]
      #6124370 - 10/08/13 09:03 AM

So.....my whole set up ....cge pro mount, 2 mallincams, guider, video switcher, electric focuser....has been giving me electric shocks....tingles when i touch anything.

This thread got me worried...

Had an electrical engineer here today...he also operates an observatory....he tested my house circuit....and.... I have no earth..anywhere.

He said its very dangerous
Told me to always wear rubber shoes at the scope ....even when the earth situation is fixed.

Phew


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