electric shock from mount

[bosun21]

5 hours ago, alacant said:

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

This can’t be for a domestic supply. There must be a neutral to produce a potential difference to produce a voltage. The only supply without a neutral is a three phase supply used mainly in industrial supplies, in which case there would be four wires. The three phases (RBY) and an earth. It’s more likely that the two wires in your supply are not the conventional color code used in the UK ie brown and blue. The Spanish electricity supply is 230v 50Hz. Do you have access to a multimeter?

Edited March 15, 2023 by bosun21
Typo

[powerlord]

7 hours ago, alacant said:

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.

Sounds like your measuring wrong. Remember it's ac so meter should be ac.

The buzz is caused by the 12v plug negative contacting the metal of a mount. If it doesn't do that internally (like with bresser), no buzz.

To stop buzz, it's just about providing a path to ground from the metal that's more favourable than your fingers basically.

This does not (and should not) be a connection to a mains plug. If you knew more, a ground on mains wiring could maybe be used, but I'd worry you might connect to live so please don't do this.

Just get a bit of wire, and connect one end to bare metal somewhere close to where u get a tingle. Temporarily first if u like to test.%

What are you standing on?

Take the other end and connect it to the ground. If earth, stuff it down a bit. Experiment with sticking it to different objects (metal ones bolted into ground ideal).

The idea to provide a lower resistance path for that current that through you.

@Carbon Brushosorry

Sorry if I didn't make it clear. By lazy I mean, because some Chinese stuff it bad, always blame it. Yes, some Chinese stuff is abysmal. But some is fine. I agree it's a bit of a lottery, but the fact some IS fine and still cheap shows how much astro companies take The biscuit IMHO.

Stu

[alacant]

1 hour ago, powerlord said:

he buzz is caused by the 12v plug negative contacting the metal of a mount.

Ah, OK. Of course. I think you've nailed it. The Bresser 12v socket is surrounded by plastic. Even if the cable does pull on the plug, the negative touches plastic.

On the eq(x) mounts it seems that even though the socket is set in rubber, even a slight pull on the plug and the negative touches the surrounding metal.

5 hours ago, bosun21 said:

This can’t be

The guy was fitting a torno (lathe I think) and was attempting to explain why you can't just plug it into the wall. Translation to technical English is not my forte.

Anyway, FWIW, apparently this is what we have at this site:

[EarthLife]

Very few switch mode power supplies (SMPS) have the output DC connected to Earth (helps prevent earth loops for one) which is why you often get a tingle, it happens with certified SMPS as well as cheap chinese ones. As has been said it's due to leakage, you get it both outdoors and indoors and is caused by the transformers coil-to-coil capacitance and the Y-Capacitor (the little capacitor that goes from the mains side to the output side).

The Y-Capacitor is there to help reduce EMI (electrical interference emissions), which to be honest is a feature of class 2 SMPS's that I find a little scary because it's a possible failure path directly from the dangerous mains circuit straight to the low voltage output.

The trouble with using any SMPS (or even linear power supplies) outdoors is you can very easily have dampness and/or condensation on the supplies PCB etc, this can easily cross the mains to low voltage output circuit (say across the HF transformer pads), especially at night. If that happens then your in danger !

It's much better to keep all outdoor voltages to a low'ish level (say 48V AC or DC and lower), that just means using either a battery system or running a low voltage supply from indoors to outdoors which then you regulate/step down at the mount to suit your needs.

Edited March 15, 2023 by EarthLife

[M40]

Your mount is probably on rubber feet which means its isolated from earth. Any potential difference that exists between the mount and the ground you are standing on will therefore go through you when you touch it. Easiest solution thats been mentioned above, is get a piece if wire and go between mount leg and the ground its standing on. Do not connect it to mains earth or the DC supply. If you can, stick a long screwdriver in the ground and wrap the wire round that. You may need to chuck a cup of water over the ground connection if the ground is very dry. Job done, let us know how you get on. All the best.

[alacant]

15 minutes ago, M40 said:

stick a long screwdriver in the ground

Hi and thanks for the suggestion. Unfortunately, this site is on a roof terrace.
 

2 hours ago, EarthLife said:

it's due to leakage

Why do I only get it with SW mounts though?

Cheers and thanks again everyone.

[EarthLife]

36 minutes ago, alacant said:

Why do I only get it with SW mounts though?

Without knowing all the technical details of your mounts and different power supplies and how you have the systems wired up etc it's impossible to say.

Do your other mounts have any possible electrical pathway to ground ?

Do the internal PCB's have there negatives connected to the mounts metal work ?

Lots of other things to know before anyone can give you that answer.

[malc-c]

Not advising you to try this, but I used to get a tingle in my fingers, mainly in the quicks of the nails, especially if I had bitten them (bad habit I know) anytime I had to do maintenance in my old salt water aquarium.  I was told to use a multi-meter, set to AC and place one probe in the tank and the other to an earthing point.  On doing so it registered around 60v AC !  - It was then a case of powering everything off, then back on one item at a time until the voltage was detected.  Turned out to be a cheap pump on the skimmer which was supposedly double insulated and thus no earth.

Getting back on topic, I can't speak for EQ8 / EQ6 mounts, but on my HEQ5 the two holes that are used to secure the board to the mount have a plastic insert with a lip that isolates the board from the mount, but then the actual power input is housed separately in a plastic housing, unlike the EQ6 which seems to have it all mounted to a metal plate.

With regards to the 13.8v mentioned above, my HEQ5 ran fine on a regulated bench PSU that provided 13.8v DC so I would presume that both the EQ6 and EQ8 will also be OK when run at this voltage.  I also agree with comments about Meanwell power units... if you buy genuine PSUs direct from Meanwell, or through authorised outlets such as RS / Digikey etc then they last and are of a high standard.  I used a constant voltage (48v 350w) supply to run my DIY aquarium LED lights.  These were on 10 hours a day, 365 days a year, for over a decade and the PSU is still as sound as it was the day I got it.

[Clarkey]

16 hours ago, Carbon Brush said:

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.

I have to agree with this. I made the mistake of buying some poor power supplies (even though they claimed to be EU spec). I got a nasty shock from one and the other literally blew up when I plugged it in.

I now use a 13.8V regulated supply, similar to the Nevada one sold by FLO. (I got it from a radio suppliers in the UK). The 13.8v is fine for all my kit and alleviates the risk of any slight voltage drops.

[powerlord]

2 hours ago, EarthLife said:

Without knowing all the technical details of your mounts and different power supplies and how you have the systems wired up etc it's impossible to say.

Do your other mounts have any possible electrical pathway to ground ?

Do the internal PCB's have there negatives connected to the mounts metal work ?

Lots of other things to know before anyone can give you that answer.

SW  mount circuit boards at least on the EQ6 screws directly to mental. whether it has a ground track that connects to that I dunno - but it sounds like they probably do.

[M40]

22 hours ago, alacant said:

Hi and thanks for the suggestion. Unfortunately, this site is on a roof terrace.

🤣 let's not try that then.

Plan B: is your roof terrace material concrete or a rubberised type coating? If it's concrete or similar, bridge between one of the mount legs and something metal fixed to the roof or try somewhere on the floor to see what happens. If its rubberised that becomes a whole new ball game as you may be getting a tickle when you touch two different parts of the mount or it could just simply be static. What's also interesting is that others have experienced it. I use both a battery and a nevada on an heq5 and have never felt a thing. 

[powerlord]

failing all else, I have some left over aluminium insulation from building my observatory

Certainly enough to make a head to toe metal suit for you. Simply place this on, while also fashioning yourself a tinfoil hat, gloves and shoes, and u should be good to go. 👍

 

[alacant]

3 hours ago, M40 said:

heq5

Thanks. Yeah. I believe Heq5s are ok because they have the power socket mounted in a rubber  block. The eq6 in question has its socket mounted in a block resembling anodised aluminium which has zero resistance. The eq8 gives directly to the metal of the mount.

[alacant]

Here is the -hopefully provisional- solution... Yes, I've touched the water supply elsewhere in the property, y nada.

No LOL please!

        

[Vulisha]

I went around home and picked all wall chargers I have and checked voltage with my water pipe :

 

OnePlus charger 0V

Realme Charger 0v

Dell Laptop 0V

Some 65W usbc 0V

Xiaomi Charger 45V

Samsung Charger 45V

Official Raspberry Pi charger 85V

+Class usb Charger 85V

12V Mount power supply 65V

24V mount power supply 65V

So all in all it is possible to isolate currents in small package, but makers are cheap! 

[Cosmic Geoff]

4 hours ago, alacant said:

Here is the -hopefully provisional- solution... Yes, I've touched the water supply elsewhere in the property, y nada.

If using a water pipe as an earth in a modern property, you should check that you have copper pipe all the way to earth, and not a section in blue plastic..

[malc-c]

Not sure about other countries, but following on form Geoff's post, in the UK the Earth bonding is (should) be connected to ground either via the outer metal shielding of the supply cable, or via a dedicated grounding rod hammered into the ground with an Earth wire run form it to the consumer unit.

Then all copper pipe work is then bonded to the Earthing point