Voltage feedback through my mount!!

[libraryman]

Perhaps an odd question but i am able to feel a small voltage tingle through my mount...i am clear about what it is, having initially thought it was vibration that i felt when moving a weight along my bar.

Clearly something is getting through ad i am earthing it when i stand on wet or damp ground.

EQ8///with all 12 volt supply regulated/

Ray

[ronin]

Others have reported the same, actually over a few years so it is not unique to you.

Cannot recall what the cause and so the cure is.

However the title is obvious and someone will come along with the cause and solution.

It will be an earth somewhere in the system but cannot explicitly state where.

[Steve Ward]

Induced current from the power supply via an earth loop , my HEQ5Pro is the same .

[libraryman]

Oh thanks guys, is it anything to worry about, i guess the answer is no

Ray

[Cath]

You must be using a switched mode power supply. It's all too common for a lot of them to leak a small amount of current through any external path made back to Earth, which is what you are feeling when you touch the mount. So long as it's not painful all should be fine.

In my view all switch mode PSU's should be designed with some kind of Earth connection to the 0V side of the output, but such SMSP's are few and far between these days

I have a cheap Pofung walkie talkie, when it's on it's charger it was down right painful if I touch it, so the first thing I did was to replace it's cheap switched mode PSU with a nice safe Earthed linear one (no more leakage current).

I much prefer the much safer linear PSU, but they are bigger and heavier for the same output power.

[Cath]

If you're feeling a little concerned about it you can always attach an Earth strap to the mount .. an Earth wire going from the mount to a copper pole pushed into the ground (or to a nearby copper water pipe).

It's a good thing to do anyway for a fixed mount like an observatory mount. It also drains away any static build-up. Any amount of static charge can easily blow delicate electronics if you're not careful.

[libraryman]

Thanks Cath, yes i am using one, my main supply is a maplin regulated supply, however, I also use a converted ATX supply for my heaters.

I assum, that's where the issue is! I have used the mount many times and it sits on a tripod in the garden on grass so its already grounded..to a degree, I've not felt this voltage before so I need to check it out.

Ray

[Cath]

mmm yes.

Have to ensure the PSU's never have any dampness (dew/condensation) inside of them as that would at some point become VERY dangerous.

If powering off the ATX PSU removes the tingling then you know where the possible problem may be.

I myself don't trust switch mode PSU's outside in the cold and damp. If they are NOT cheap chinese PSU's and their PCB's are dry and warm then it's probably OK, otherwise I'm not happy with it.

I just don't like PSU's that tingle, I don't like the un-earthed leakage currents that are common (and accepted as being normal) these days with switched mode PSU's, I see it as lazy/sloppy design work from the design engineer.

[libraryman]

o.k. Cath, ive done some research and it appears that perhaps switched mode supplies, though very good, are not ideal for my purposes.

although i use them in a sealed enclosure, they are prone to damp, clearly that's not ideal. it may be the case that with the damp weather i am seeing leakage that wasn't experienced previously.

in this case. the use of a linear regulated power supply may be preferable and could be a better option, 

will the use of said regulated linear supply cure the earth leakage issues completely?

Ta for you opinions

Ray

[Cath]

Only if that too doesn't get damp. Dampness in any PSU is dangerous. Just that switched mode PSU's has less of a physical mains<>user barrier than linear PSU's tend to have.

Presume your ATX power supply is definately the culprit of this newly occuring tingly sensation then ?

[libraryman]

Cheers Cath, i have tested it and found the problem...it's the USB from my camera QSI583. what happens is...i remove the power supply from the camera or its attendant USB cable from the hub or from the camera and the voltage leak stops.

So...i am guessing that the issue is with the camera power supply (switched mode supply) getting through to the USB ,  this is supplied separately from mains in my power box. 

i do not have anther supply to test it with yet so I'll sort that out...i wanted to change that supply anyway but i only have 13.8V from my Maplin unit and the QSI only likes 12Volt so it has its own supply

(i don't want to trust the ATX unit for the camera) 

Half way there 

Ray