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AC/DC converter : touch leaks and touchscreen issues


Junior Member level 1
Mar 8, 2008
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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,
According to datasheet it's a Class I device. Should not be operated without PE connection.
So yes, your aluminium box needs to be earthed. Is there an earth wire in the mains cable? 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.
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.
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? 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 of the ones off Farnell. With Diff and Comm mode filtering inside it.
Schaffner filter.

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

Having said all 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?
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