grounding multilpe PSU

[duende]

Hi,

I'm building an equaliser, i've made the pcb and i have one PSU for audio and a PSU for relays. I would like to power the unit with external PSU with a power transformer per PSU.

On the PCB the OV from the audio PSU is serparate from the relays ground.

I have to connect :

+18v
0v
-18v

+12v
ground

Chassis ground

What's the best way to connect 0V, relay ground and chassis ground for you ?

I'm planning to connect chassis ground to earth in the PSU case and connect it to the eq case, and connect all the other in the eq case, but i really need to connect all audio and power "ground" ?

And the best way is in the PSU or in the case ?

If i connect the chassis ground with the relays ground and i don't connect them to the 0V and audio ground what happen ?

Sorry for my english...

Thanks

 

[JohnRoberts]

Start by connecting all grounds together and see how that works.

You don't want the relay current to corrupt clean audio signals, so treat them differentially when possible.

JR

 

[duende]

Thanks,

Yes but in the PSU or in the Equaliser ?

 

[Bo Deadly]

Unfortunately this subject has been covered so many times people might be a little burned out on it. Try Googling this:

  site:groupdiy.com grounding

but also try different words like earth, power, hum, etc. If you look at my posts through my profile you'll see I posted a graphic about grounding with a remote PSU about 2 weeks ago. I think it was more about SMPS but the discussion is still directly applicable.

 

[abbey road d enfer]

On the PCB the OV from the audio PSU is serparate from the relays ground.

What's the best way to connect 0V, relay ground and chassis ground for you ?

It's difficult to answer because we don't have all the elements of the puzzle.

I'm planning to connect chassis ground to earth in the PSU case and connect it to the eq case, and connect all the other in the eq case, but i really need to connect all audio and power "ground" ?

You may find that the way the power supply "ground" is connected to earth is more important than how grounds are connected furhter.

And the best way is in the PSU or in the case ?

For sefety, the PSU "ground" must be connected to earth at the mains inlet and to the chassis. So it's in the PSU.

If i connect the chassis ground with the relays ground and i don't connect them to the 0V and audio ground what happen ?

Nothing in particular, because the audio "ground" is also connected to the chassis, not necessarily at the same place as earth. Since you mentioned the relay circuitry is floating, it can't produce current spikes into the audio ground. If the 12V supply uses a separate transformer, you need to ground the 12V circuit in the PSU.

 

[duende]

Hi,

Thanks, after 2 month the project is always in standby. At the moment I haven't time to work on the psu and doing some test...

Thanks for the reply but it's not clear for me, principally cause i don't speak english. I plan to connect all the ground to the earth/chassis in the psu case and run separately 0V and relays psu ground to the eq case and connect only relays ground to the chassis eq.

Maybe i will insert switch to another grounding option.... 

 

[ruffrecords]

Check this out for basic guidance:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/SimpleMixer/grounding101v2.pdf

Cheers

Ian

 

[abbey road d enfer]

Safety requirements are often contradictory with performance optimization.
The PSU's reference points should be grounded in the chassis to the safety earth.
In the remote unit, connecting again the reference to the chassis can result in a ground loop. It is perfectly acceptable to connect the reference to the chassis via a suitable RC circuit, typically a 100nF cap in parallels with a 100r resistor. However it's not always adequate, particularly in the case the remote unit has mic inputs, for which the chassis constitutes the return path for phantom power.
For an EQ with line I/O's, that shouldn't be a problem.

 

[duende]

Thanks, it's way more clear!

On the pcb the OV and "relays OV " are separate and powered from separate transformer, so OV is the reference and relays OV can act like chassis to chassis + power relays 0V ?

I ordered 5 pin for the psu cable the last week to do :

pin1  0V
pin2  +15V
pin3. -15V
pin4  0V from second power supply
pin5 +12V / chassis


If i understand correctly the best way is to use a 6 pin connector and use pin 6 for chassis to chassis, but with a 5 pin it's acceptable you think ?

And if i connect with a RC , the best way is to connect it from OV or relays OV ?

Thanks!

 

[abbey road d enfer]

Thanks, it's way more clear!

On the pcb the OV and "relays OV " are separate and powered from separate transformer, so OV is the reference and relays OV can act like chassis to chassis + power relays 0V ?

I ordered 5 pin for the psu cable the last week to do :

pin1  0V
pin2  +15V
pin3. -15V
pin4  0V from second power supply
pin5 +12V / chassis


If i understand correctly the best way is to use a 6 pin connector and use pin 6 for chassis to chassis, but with a 5 pin it's acceptable you think ?

As long as there's a wire that connects earth, you're good. No need for it to be 100% separated from the rest.

And if i connect with a RC , the best way is to connect it from OV or relays OV ?

Since there are two xfmrs, both should be earthed (unless they are the double-insulation type). So you do what you want, it doesn't matter.

 

[duende]

Ok thanks !