electric shock from mount

[alacant]

Hi everyone

Well, not exactly a shock, more a surprise 'tingle' when touching the metal part of the mount/telescope/focuser/camera. Happens with most mounts.
I have tried two cheap 12v 5A switch power supplies, one with a three pin and the other with a two pin mains lead.with the same result. 

I'm told I need either a car battery or a linear power supply to lose the leak. I don't want the former so, having a look around, I found this:

https://es.aliexpress.com/item/1005004349595403.html?spm=a2g0o.productlist.main.113.6844356e6DaLnO&algo_pvid=ce93851a-1906-4092-85b6-be4e2e6d8410&algo_exp_id=ce93851a-1906-4092-85b6-be4e2e6d8410-56&pdp_ext_f={"sku_id"%3A"12000028856749257"}&pdp_npi=3%40dis!EUR!102.1!66.37!!!!!%402100bc5c16787906922808092d0737!12000028856749257!sea!ES!168948195&curPageLogUid=YICs6qqBuMUx

Would that be any good? Alternatives you have tested personally?

I've no idea about electrics so any help or guidance anyone could give would be most gratefully received.

TIA

[Mr Spock]

Not sure about the electrics. My former EQ-6 had tingly legs though with a Halfords mains power supply. A bit disconcerting but harmless (probably).

[Carbon Brush]

I think the answer lies in the second line of your post - two cheap 12V 5A power supplies.

If you buy a well known brand of power supply, the tingling will stop.
Consider TDK, Meanwell, Cosel, Nevada to name a few.
Look for safety approvals on the product (CE, UL, etc) then go to the manufacturers web site and download copies of the certificates and test reports.

Using a cheap power supply power on expensive equipment can harm your health and your wallet by wrecking the electronics.

Avoid the strangely branded stuff from China. It is usually landfill quality.

[Bruce Leeroy]

I get the same from a Celestron SE mount.

[Carbon Brush]

The tingles are caused by leakage within the power supply.
It is from the mains (kill you easily) side to the (supposedly isolated and safe) low voltage side.

There are multiple explanations for the leakage - which apply depends on the individual power supply.
The explanation is more than a couple of lines.
But the bottom line is you have either a power supply you should replace, or a problem in your mains wiring/cable.

It is NOT the fault of the mount.

HTH, David.

[Cosmic Geoff]

As stated above, the problem is in the power supply. 

As a safety measure, you could earth the mount, either by wiring it to a stake in damp ground or to the earth of the mains supply.  I earthed my multi-satellite dish (powered via mains-powered boxes) to a water pipe, just to be safe when I was messing about with it on the flat roof. 

If earthing the mount causes a fuse to blow, congratulate yourself on a lucky escape.

[Anthonyexmouth]

1 hour ago, alacant said:

Hi everyone

Well, not exactly a shock, more a surprise 'tingle' when touching the metal part of the mount/telescope/focuser/camera. Happens with most mounts.
I have tried two cheap 12v 5A switch power supplies, one with a three pin and the other with a two pin mains lead.with the same result. 

I'm told I need either a car battery or a linear power supply to lose the leak. I don't want the former so, having a look around, I found this:

https://es.aliexpress.com/item/1005004349595403.html?spm=a2g0o.productlist.main.113.6844356e6DaLnO&algo_pvid=ce93851a-1906-4092-85b6-be4e2e6d8410&algo_exp_id=ce93851a-1906-4092-85b6-be4e2e6d8410-56&pdp_ext_f={"sku_id"%3A"12000028856749257"}&pdp_npi=3%40dis!EUR!102.1!66.37!!!!!%402100bc5c16787906922808092d0737!12000028856749257!sea!ES!168948195&curPageLogUid=YICs6qqBuMUx

Would that be any good? Alternatives you have tested personally?

I've no idea about electrics so any help or guidance anyone could give would be most gratefully received.

TIA

Seems too close in price to a well respected and well built PSU. 

I've always used Nevada units and never had a single issue. 

https://www.nevadaradio.co.uk/product/nevada-psw-30h/

 

As someone else said, the clue is in the word "cheap"

[michael8554]

Earthing arrangements may well be correct in the PSU, if it has a 3-pin mains connection.

After that the output is DC +/- with no earth.

So +12V could be "floating" on a much higher voltage.

Michael

[bosun21]

Is the tingling repeatable? It could just be static you have built up wearing anything acrylic.

[Carbon Brush]

Significant energy coupled to a supposedly floating output suggests (among other things) absence of an interwinding screen on the switching transformer.
Back to my earlier comment on certification. Insulation withstand and construction methods are specified by BS, EN and other standards.

Are we really trusting a cheap PSU, with demonstrated leakage, while standing on wet grass?
If in doubt, buy a PSU approved for medical use. Look for MOPP in the certification.

Assume you are assembling a complex astro setup. That is mount, camera, laptop, guiding, etc.
Something in there will probably have an earth that you cannot avoid, and is not notified on the box.
For example, typically a laptop has the USB 0V connected to mains earth.
Adding another earth to compensate for a dodgy power supply is inviting other problems.
If an earth is used 'in anger' due to an insulation failure, the fault current flows down the USB lead to the laptop motherboard.

Recently while carry out safety approvals testing on equipment that had a laptop connected, I fried the laptop.
The earth bond test current (25amps) is intended to duplicate what happens when a power supply insulation breaks down.
Though actual mains fault currents can be much higher.
In this case multiple connections between equipment under test and various test instruments meant I forgot the USB in the laptop.
Fortunately I was deliberately using a very old laptop because of the risk. No hit to the wallet.

I don't understand how we spend £££ on mounts, £££ on cameras then skimp on the power supply.
A dodgy power supply can so easily fry mounts and cameras.
There was recent thread where a user fried an expensive camera (and more) due to a simple mix up on 5V and 12V interchangeable plugs.
Because we don't put overvoltage protection anywhere else, we are unprotected. Sorry drifting off topic.

Electrostatic shock is something very different and momentary.
It can though be very damaging to modern electronics. Another big (off topic) subject.
More relevant to indoor kit assembly and observatory use. Standing on wet grass prevents static build up!

[alacant]

Thanks everyone.
As the tingle is always there, I think I can rule out static. So, coming back to the car-battery-or-linear-psu advice, can anyone recommend a substitute for a cheap 12v 5A model?
@Anthonyexmouth thanks for the specific psu (exactly what I need) but I think the link points to a switching model of 13.8v.

So, anyone any recommendations for a 12v 5A linear psu?

TIA

[Anthonyexmouth]

46 minutes ago, alacant said:

Thanks everyone.
As the tingle is always there, I think I can rule out static. So, coming back to the car-battery-or-linear-psu advice, can anyone recommend a substitute for a cheap 12v 5A model?
@Anthonyexmouth thanks for the specific psu (exactly what I need) but I think the link points to a switching model of 13.8v.

So, anyone any recommendations for a 12v 5A linear psu?

TIA

Switch mode is fine. 99% of setups out there are using one. 

 

Edit: Also worth considering more than 5A rating. Start adding dew bands or other accessories and you'll soon need more. Cheaper to invest now in something that'll grow with you. 

Edited March 14, 2023 by Anthonyexmouth

[CraigT82]

This Lynx Astro one is actually a Meanwell unit, I tried to find it cheaper elsewhere but no results so bought from FLO. worked perfectly fine for me with my EQ6. 
 

https://www.firstlightoptics.com/power-accessories/lynx-astro-12v-dc-5amp-low-noise-mains-power-supply.html

[Elp]

Never experienced the above, via mains power or through my Celestron Lithium LTs, the weather is also usually cold or damp.

[powerlord]

Hmm. If u don't mind me saying so, a bit of misinformation here (speaking as an electronics engineering grad). Just ensure the metal is grounded through a link to ground (I. E. The ground) rather than through you.

Of course it may be you do indeed have some killer psu.. So just my 2c..but imho the excuse of 'cheap Chinese psus' is a lazy one. It doesn't justify the silly pricing of astro ones. A decent 12v psu costs peanuts these days. And there are few application these days that need inefficient linear regulars, and our kit is not one of them. Just add an earth path from the negative. If it still does it.. Summit is up.

Stu

 

[markse68]

It's very common with switching psu's with their high frequency switching and floating isolated outputs- a phantom coupling somewhere. We use meanwells a lot at work- decent brand but if you touch between 2 systems you can feel a high frequency "hum" and if you touch with your elbow, a tingle. With a meter it measures 60V ac. I don't think it's anything to worry about in terms of safety as there's no current and if you connect the DC GND to mains earth then it's not isolated anymore

Mark

[Alien 13]

22 minutes ago, markse68 said:

It's very common with switching psu's with their high frequency switching and floating isolated outputs- a phantom coupling somewhere. We use meanwells a lot at work- decent brand but if you touch between 2 systems you can feel a high frequency "hum" and if you touch with your elbow, a tingle. With a meter it measures 60V ac. I don't think it's anything to worry about in terms of safety as there's no current and if you connect the DC GND to mains earth then it's not isolated anymore

Mark

I treat this annoying tingle the same way I would noise in one of my Valve amp designs that have separate ground and signal earths tied together with a 1-10 K OHM resistor with a 10 nano farad cap in parallel with it. 

Alan

 

[alacant]

1 hour ago, powerlord said:

Just add an earth path from the negative

Thanks

Would this prevent the tingle? If so, how would I do that? The DC end has has a standard 5.5 X 2.1 plug.

TIA

[Vulisha]

I am having exactly the same issue, I swapped Chinese PSU for relativelly expensive local psu, ended up being basically the same on the inside. You can test it with electrician screwdriver/tester, it glows a bit. 

And I use shelly smart switch, that switch cuts of just one line, and in Europe you can rotate as you wish. So if you rotete it "incorrectly" and live wire iz not cut off, it zaps even more. 

[windjammer]

This might be relevant

https://eng-au.faq.panasonic.com/app/answers/detail/a_id/21694/~/troubleshooting---why-am-i-getting-a-tingle-when-connecting-a%2Fv-products%3F

I have also read it can also be caused by somewhere the ground and neutral are connected - which could be anywhere in the house wiring.

It is a very annoying problem to try and track down and fix - let us know how you fix it!

Simon

 

[Carbon Brush]

3 hours ago, powerlord said:

So just my 2c..but imho the excuse of 'cheap Chinese psus' is a lazy one.

Sorry but I completely disagree.
I have seen for myself too much cheapie chinese kit with under-rated mains cables, fake fuses, too high rated fuses, extracts from regulations posing as test certification.
Obviously not all in the same equipment! But far too much for anyone to claim it was a bit of bad luck.
When I have challenged chinese suppliers on this, they have lied - and no it was not problems with translation.
You could add to this similar horror stories from test houses and other professionals.
If you have a known brand purchased via a traceable path you are generally safe.
If it is from an ebay seller, amazon marketplace seller, alibaba, sunday market...Enough said.

2 hours ago, markse68 said:

With a meter it measures 60V ac. I don't think it's anything to worry about in terms of safety

Safe for you. What about if this is connected to a high input impedance, voltage senstitive circuits such as camera ports, or even handset ports.
Not everyone includes TVS devices or other protection.
You can easily do serious damage to modern electronics with low voltage.

Returning to the OP. He says he is not electrically knowledgeable.
We have no idea if his consumer unit (AKA fuse box) was installed by a failed apprentice to Faraday, or is modern fully compliant, with RCD protection to sockets and a recent test certificate.
We have no idea if his mains extension lead (which is presumably in use) has been trapped in doorways and lost the earth, or is carefully tended and installed.
We can therefore only recommend that he assures his safety from an approved power supply.

HTH, David.

[Moonshed]

All I can add to the conversation is to say that the only time I have received an electrical tingle when using my kit is when I have used a dummy battery in my Canon. Feeling sure there must be a wiring problem with the dummy battery I ordered a new one but have not had the opportunity to try it out yet. If the new one gives a tingle then I’m stumped and will have to stop using it because the tingle is such that I cannot work with it, too strong to keep my hands in contact with the mount. It will be back to the Canon battery and hope it doesn’t run flat mid-run or that I forgot to charge it.

[Vulisha]

So all in all if I get this meanwell I, and OP are good? 

[alacant]

5 hours ago, powerlord said:

Just add an earth path from the negative

Thanks

Would this prevent the tingle? If so, how would I do that? The DC end has has a standard 5.5 X 2.1 plug.

TIA

[alacant]

A few tests with the mounts we have tonight.

Cheepo PSU 12v 5a gives tingles with both SW eq8 and eq6 but not with Bresser exos2. Same mains plugs, leads and sockets. The eq8 motor plug alone is fine using a similar 12v 5a (yes, we swapped them around too) It's only when the hub is plugged in do we get the buzz.

Does that help us?

Cheers 

Edit: we're in Spain. We have two lives @ around 110v each. No neutral.

Edited March 14, 2023 by alacant