So i've got a cheap buck converting power supply for my Due Board and i'm seeing strange effects.
Basically i'm measuring a distorted 50Hz Sinus at 120V peak, between the OSC ground and the power supply ground.
When i close that circuit with my hands it feels like a real 120V sinus does. So it got power behind it.
Now my theory is that the power supply uses one of the 230V lines as its ground (since it is not grounded itself).
Can this be happening? I'm seeing the same effect with another similar power supply.
Please describe the electrocution feelings in more detail when you touched the high voltage wires. Are you sure AC electrocution feels different than DC electrocution? Compact fluorescent light bulbs have 600 volts available when unplugged and laying broken on the floor. It is DC 600 volts when unplugged for clean-up.
Now my theory is that the power supply uses one of the 230V lines as its ground (since it is not grounded itself).
There should be isolation between the power supply and the mains. However you will get some leakage that will tingle when it floats.
This is normal for this sort of supply and is not dangerous. When it is grounded it should be fine.
If not then there is a fault on it.
AmbiLobe:
Please describe the electrocution feelings in more detail when you touched the high voltage wires. Are you sure AC electrocution feels different than DC electrocution? Compact fluorescent light bulbs have 600 volts available when unplugged and laying broken on the floor. It is DC 600 volts when unplugged for clean-up.
Well you can feel the AC, just as easy as you can hear 100Hz.
Grumpy_Mike:
Now my theory is that the power supply uses one of the 230V lines as its ground (since it is not grounded itself).
There should be isolation between the power supply and the mains. However you will get some leakage that will tingle when it floats.
This is normal for this sort of supply and is not dangerous. When it is grounded it should be fine.
If not then there is a fault on it.
It says on the data sheet double insulated. That means it is isolated. The transformers are not big because they do not carry much current and only isolate. That is they are one to one and wound on a torriode.
It also says leakage current at 0.25mA.
Grumpy_Mike:
It says on the data sheet double insulated. That means it is isolated. The transformers are not big because they do not carry much current and only isolate. That is they are one to one and wound on a torriode.
It also says leakage current at 0.25mA.
Which is quite a bit of leakage, hence you can feel it. 2mA is theshold of pain, things get dangerous quite
quickly above that, best to ground the output 0V line of the supply.
That doesn't seem 100% safe to me... I've never felt a tingle from a (properly working) low-voltage power supply.
A long time ago, my mom said she felt a tingle from the waffle iron. I was wearing sneakers and I couldn't feel anything. So, with one hand on the waffle iron I reached-over and briefly touched the water faucet. See... I was "smart enough" to know how to get a complete circuit... WHAMO! 120V across my chest! I recommeded that she get a new waffle iron, she did, and I'll NEVER try THAT again!!!!
Yes it is. It is quite common. I can feel tingling on most powered devices these days.
The waffle iron is a diffrent matter, there would be no switch mode power supply in that and it looks like the fault you had might have been picked up if you appliance was earthed. If it was earthed then it sounds like your house wiring is faulty.
