AC/DC converter : touch leaks and touchscreen issues

[SG61-addict]

Hello,

I have a complex project :
- RF board
- BMS board + Li-ion pack
- CPU board based on a rpi compute module
- Large LCD screen with capacitive touch panel (this one)

All theses items are inside an aluminium box.

I am using a 230V to 24V/2.5A AC/DC power supply to charge the battery.

The AC/DC is a meanwell GST60A-24 : datasheet

The datasheet indicates a maximum leakage current of 0.75mA under 240V.

In practice :
- When touching the aluminium box, I can feel a non-dangerous but uncomfortable current.
- The DMM measures a 75Vac between the box and the ground, and 250µA leaks.
- Through the human body, the leaks is limited to 100µA (65-70Vac).
- The worse thing is that the capacitive touch screen works very bad when the power supply is connected.

I have found 20-30 AC/DC power supplies from meanwell, power pax, XP power, CUI... all have a 250 to 750µA leakage current.

My main objective is to get the touch screen working in all conditions. Should I use another PSU, or add some filtering somewhere ?

Thank you,
Regards

 

[FvM]

According to datasheet it's a Class I device. Should not be operated without PE connection.

 

[cupoftea]

So yes, your aluminium box needs to be earthed. Is there an earth wire in the mains cable?...you could use that to earth the aluminium box.

At the moment, you are getting a wee shock current through the Y capacitor that is connected across the isolation barrier of the meanwell power supply.

 

[SG61-addict]

Yes, there is a earth wire in the mains cable but it is not connected to the GND of the output DC jack.

I have no way to connect the aluminium box to the earth. It looks that the only option I have is to change the power supply.

 

[cupoftea]

Hi, Can you somehow connect your circuit (isolated side) 0V to the chassis with a Y capacitor?
Also, What about connecting line and neutral to the chassis also with a Y capacitor?...as you know, be careful with this.
I mean it would be nice to do a cable cut down and grab the earth wire out of the cable and connect earth to your chassis,
but maybe its not a good idea for safety sake.

Any cable ferrites to squeeze round the mains cable?
Or a ferrite torroid to wind a few turns of the mains cable through it.
Or a common mode choke for you to fit in the mains cable.

What about a mains filter module to fit in the mains cable......one of the ones off Farnell. With Diff and Comm mode filtering inside it.
Schaffner filter.

https://www.schaffner.com/product/FN332/Schaffner_datasheet_FN332.pdf

What about connecting chsassis to neutral with a 100k resistor......be extremely careful...dont mix it up with line conductor....thats why i said via an 100k resistor 1w+ rated.

Having said all this...you cant put a hole in the Alu, and a screw and nut and somehow get earth out of the cable with a cable cut down?