I've recently bought a D-Link DIR-300 wireless router. While disconnecting its power supply from it, I got a tingling sensation when I touched the plug (to be clear, I'm talking about the 5V DC plug, not the mains plug).
An AVO meter shows about 90V AC to earth from either side of the 5V plug. Short circuit current to earth is about 0.1mA.
Still, I thought these things were meant to be completely isolated. Has there been a change of approach?
Sylvia.
Apparently it's normal, and is related to RFI suppression.
Sylvia.
Sounds like a small cap from mains.
Just think, the only thing between you and the great beyond is a thin layer of ceramic material, possibly contaminated with who-knows-what, bearing a certification logo of dubious authenticity. It's time to invest in some rubber-soled slippers.
-- Joe
It's certainly not a happy thought. I will be treating the low voltage side of such power supplies with more respect from now on.
BTW, I tried the same tests with the power supply for my cable modem. It showed higher voltages, but lower current.
But immediately after I'd unplugged it from the mains, I happened to touch the mains plug pins with the palm of my hand, and got a significant shock off it. Reverse leakage through the rectifiers? But why should there even be enough to feel?
Sylvia.
That is also quite normal ! There is one or more capacitors across the supply pins. They can be left in a charged state at the instant you pull the plug.
The voltage you measured on the output side was simply due to the leakage capacitance of the transformer or if a switch mode psu the capacitors on the supply side having a connection to the common rail.
Do you mean a *real* Avometer Sylvia? As in model 7 or 8?
100 uA is usually below the threshold of sensation (usually about 1 mA), but some people can sense current of lower value. If it has a three prong plug, it may have capacitors to ground. There is also some capacitance from the primary to secondary windings, especially if they are layer wound. The shock you got from the plug after disconnecting from the mains may have been from an RFI filter capacitor that was still charged. If you touched across two blades of the plug, that might explain it. If you only touched one blade, then there must have been another return path to ground, such as the secondary output to a chassis ground, and you would have had to touch something else grounded, or be wearing very conductive shoes. If it is a switching supply, there is a fairly large electrolytic charged to about 180 or 360 VDC, and maybe there is reverse leakage through the bridge rectifier. You might check for DC voltage on the mains plug blades after disconnection.
Paul
Use some common sense. Oh, that's right, you do not have any.
Look at how stupid your question is, and you will already have your answer.
You're an idiot, and it is related to your 100% lack of grasp of electronics.
Please do us all a favor and latch on to the high side of one soon.
You're a total retard, and you likely do not even know how to make such measurements.
Damn! Obviously not significant enough!
You're an idiot. You don't even know what type of circuit the dongle is constructed with. You won't know either, until you pull out the dremel tool, and stop guessing like the twit you are.
Sounds typical.
Perfectly allowable under IEC60065.
I bet I even know which component's causing it.
Graham
100% correct. It'll almost certainly be a Y2 cap between the live and secondary sides of the switching transformer.
Go to powerint.com to find out why it's there.
Graham
It HAS to be TWO caps or a single cap of special construction incorporating a safety barrier (Y2).
Graham
That's another cap ! You're not meant to touch the power pins immediately. It's all in IEC60065.
Graham
YOU obviously haven't a clue what it is.
Graham
On Mon, 09 Mar 2009 02:18:22 +1100, Sylvia Else put finger to keyboard and composed:
See this DVD player PSU circuit:
Notice capacitor C8 at the top LHS. It is a Y1 type that connects the the primary common to the secondary ground. That's what is giving you the tingle.
IME TVs often have a high value resistor and capacitor linking the reference points on both sides of the switchmode transformer. For example, my Sanyo TV has a 5.6M resistor and two 2200pF caps between the negative terminal of the main 400V filter cap on the AC side and the 0V reference on the DC side.
|---- R ----| |- C --- C -| _|_ _|_ = ===
This article talks about X and Y line-filter capacitors:
- Franc Zabkar
Since you cannot know exactly what type of dongle circuit is being used (especially from that dumb twit's description), you cannot possibly know what component you "think" is causing the problem you "think" exists.
A few years back was the end of my tenure of ten years in making power supplies, you retarded twit.
I have even designed custom entry modules, and if you know what that term refers to, then you know your claim is invalid, you retarded f*ck.
Try this one. Run an electric drill, then unplug it. Get a "friend" to hold the plug in his hand, prongs inward. Squeeze the trigger.
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