• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Earthed 12V Mains adaptor

riccardo

Member
Do mains adaptors with the DC ground connected to earth exist? / Where could I buy one?

I am making a device which is powered from a 12V, 1A mains adaptor. The device has a high voltage DC module in it which outputs about 20kV. The way it is used, the high voltage is discharged into the air, and therefore doesn't directly return to the DC GND.

This causes a problem where a typical isolated mains adaptor will become oppositely charged until I can hear little discharges occurring inside it. My workaround for this is just earthing the DC GND rail via an ESD plug (internal 1M resistor). This works fine except it for the inconvenience of having two separate plugs.

Does anyone know of a PSU with this integrated, or a mains adaptor that could be disassembled so I can make the modification internally? (Most seems to be glued together or have a plastic earth pin)
 

alec_t

Well-Known Member
Most Helpful Member
You could use the ground connection available in a multi-socket adaptor and just plug the 12V adaptor into one of the sockets.
 

ronsimpson

Well-Known Member
Most Helpful Member
Ground Wire as one of the Current Carrying Conductors
On the power line side there is (line, line, ground) or (line, neutral, ground).
On the isolated side there is 12-V and 12-return. The 12-V gets turned into 20kv at 300uA. (assuming 50% efficiency) Probably less current.
The 300uA for the high voltage is returning to the 12-return. (12V ground) I do not see it running through the green wire.
Because the 12 volt supply is isolated it can float off to some voltage. Probably a 1 meg resistor to green wire ground will keep it some where near 0 volts. I think only a couple of u amps will keep it near ground.

Years ago I talked with CSA, UL, and VDE about running current on green wire. "on current" So I asked about 1uA. They said that 1uA=0. So I asked about 10uA and they said 10uA=0. Then they said 100uA=0A. After much talking they decided that "no current" is a current level so low that you can not get shocked by it. I have battled this many times and often the "0 current" is 5mA or 2mA, it seems to change every time.

Bottom line is that the high voltage current is not flowing in the green wire. The current wants to flow from 12kv to 12-return.
 

EE World Online Articles

Loading

 
Top