I need a lesson in ground connections

Thanks Frank.

To try to help… If mains voltage is entering inside your enclosure (ie. not a wallwart), your ‘conductive’ chassis should ALWAYS be connected to ‘mains ground’. As for the secondary circuit ground, if ‘mains voltage’ is inside the enclosure, it is a very good idea to connect it to ground as well. Or… just run everything off wallwarts.

Whats the difference of a Wallwart and a PSU whichs secondary Side ( you know, the Plug from the wall wart…) is not connected to Protective Ground? Would you get a wire that connects the Wallwarts GND to your Mains Protective Ground? See?

Can we please all try to not kill ourselves?

All you need to know is the good old engineering rule to never connect secondary (in your case the DC +12/+5/GND/-12) Side of a PSU to the Primary (230V AC) Mains side and you are good to go.

If this results in hum, noise or other problems its more likely a problem of you in-house mains installation and all other tricks you may read about are just workarounds that might be dangerous. Id rather call an Electrician to check the Installation than use a Ground Lift Switch.

Frank, you’re right in one point, that is if you do not connect ground to protection earth, you don’t need a ground lift switch. Because you - so to say - hard wired that switch to OPEN. but you’re wrong in that this is an engineering rule. It is just dangerous not to connect those grounds.

Ask an electrician. If you don’t believe an electrician.


Whats the difference of a Wallwart and a PSU whichs secondary Side ( you know, the Plug from the wall wart…) is not connected to Protective Ground? Would you get a wire that connects the Wallwarts GND to your Mains Protective Ground? See?

Answer: The mains stay inside the wall wart, i.e. they will NEVER be able to touch anything inside your chassis. That’s the big difference. Read the VDE

Don’t want to come across like a smartass. Bad advice can be lethal here.

@fcd73 :slight_smile: The ground wire should be viewed as a safety net. If the ‘mains live wire’ breaks and directly connects to the secondary, it has nowhere next to go. The path with least resistance could easily be you. The wallwart ‘might’ do the same thing… but it should have gone through rigorous testing and certifications etc. and… at least your relatives have someone to sue if you do get zapped!

Now comes the tricky part…. then why isn’t then “COM” Terminal on the Meanwell - the GND for the secondary side - connected to the Ground Terminal by default?

Just asking as this would make sense seen from your point of argumentation to hardwire this so no dumb person like me can forget about it?

well you’re not dumb, second i would say it’s because you might want to do the star grounding at some other point than inside tha case of your meanwell psu. Usually you would do that at a screw in the chassis near the power inlet where the PE comes from.

I’ve researched the issue a few years back, and found a good pdf from musikding i believe, where it explained schutzklasse 1 (for example you also don’t solder stranded wire in psu circuits, always crimped connections), i see if i have it bookmarked, or on my disk.

Just took apart some Devices and found both approaches - connecting PE to GND Plane and not - but always the PE was connected to the Metal Chassis.

German Schutzklasse 1 just states that you should not connect PE and NC when your wires are less than 10mm, it doesn’t define wether to connect secondary PSU GND to PE or not.

I guess we both are as dumb as smart. Now ill go to the attic and get my DUBBEL to have a look :wink:

Ok here the pdf and another one from PAiA, check the symbols at the G point secondary ground.

According to your Merkblatt connecting the PE and Secondary Side GND is “zulässig” which means allowed, not mandatory as long as the secondary voltage is lower than 50V in respect to PE.

EDIT: One beauty in german engineering is that you always will find lots references to Standards (here its VDE 701-702) but the Standard itself can only be bought for lots of money….

This connection one time saved myself and my beloved old old Shruti-1 (no H) from electrocution. We were sitting in a caravan and had power from i don’t know where, Shruti connected to an old tube radio. The cables were hanging all around the caravan (my buddy’s preferred method of living) so while i was giving a demo of the sound someone moved, touched a cable and the radio took a dive from the desk to the floor, making all kinds of shorts, and died. I could feel with my fingers that there was a current flowing and all, but neither I nor the synth with AVR and all had any problems afterwards.

@fcd72 ok you win!
but i still do it that way, even for myself

Ok i read it again. The chassis itself must never be disconnected from PE. So in the case of Euro Modular where signal GND is always in contact with the chassis (1/8 jacks) there is really no other way. If you earth the chassis you automatically connect both circuits anyway. If you do it deliberately with a thick wire you at least make sure this is the connection with the lowest resistance.

So i just called someone who is more clever than rosch and me - not only added but multiplied - and sadly he was sitting in the car but he promised to get back to me tomorrow as this would be a bit longer explanation. So stay tuned.

For the meantime he comforted me with the fact this will be a rather pointless discussion because in next to all setups there will be some piece of equipment that ties secondary GND and PE together - it strikes again, the normative force of the factual!

now now more clever than you and I not only added but multiplied - that rules out Marcel Reich-Ranicki and Harald Lesch… can only be Frau Merkel then, didn’t know you have her private number…

edit: just found out, M.R.R. died last year. Quite a loss, compared with other TV figures

In fact its more Olli Schulz than Angie….

edit: under what stone where you hiding rosch???