Tingles from power supply

[Sylvia Else]

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.

 

[Sylvia Else]

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.

 

[Dirk Bruere at NeoPax]

Apparently it's normal, and is related to RFI suppression.

Sounds like a small cap from mains.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
http://www.theconsensus.org/ - A UK political party
http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff

 

[J.A. Legris]

Apparently it's normal, and is related to RFI suppression.

Sylvia.

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.

 

[Sylvia Else]

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.

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.

 

[Baron]

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.

 

[MoiInAust]

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.

Do you mean a *real* Avometer Sylvia? As in model 7 or 8?

 

[Paul E. Schoen]

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?

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

 

[Archimedes' Lever]

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.

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.

 

[Archimedes' Lever]

Apparently it's normal, and is related to RFI suppression.

Sylvia.

You're an idiot, and it is related to your 100% lack of grasp of
electronics.

 

[Archimedes' Lever]

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.

Please do us all a favor and latch on to the high side of one soon.

BTW, I tried the same tests with the power supply for my cable modem. It
showed higher voltages, but lower current.

You're a total retard, and you likely do not even know how to make such
measurements.

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.

Damn! Obviously not significant enough!

Reverse leakage through the rectifiers? But
why should there even be enough to feel?

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.

 

[Eeyore]

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.

Sounds typical.

Still, I thought these things were meant to be completely isolated. Has
there been a change of approach?

Perfectly allowable under IEC60065.

I bet I even know which component's causing it.

Graham

 

[Eeyore]

Apparently it's normal, and is related to RFI suppression.

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

 

[Eeyore]

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.

It HAS to be TWO caps or a single cap of special construction incorporating a
safety barrier (Y2).

Graham

 

[Eeyore]

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?

That's another cap ! You're not meant to touch the power pins immediately. It's
all in IEC60065.

Graham

 

[Eeyore]

You're an idiot, and it is related to your 100% lack of grasp of
electronics.

YOU obviously haven't a clue what it is.

Graham

 

[Franc Zabkar]

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.

See this DVD player PSU circuit:
http://www.users.on.net/~fzabkar/DVD/Sunplus/G1928/G1928_PSU.gif

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:
http://my.execpc.com/~endlr/line-filter.html

- Franc Zabkar

 

[FunkyPunk FieldEffectTrollsistor]

Sounds typical.



Perfectly allowable under IEC60065.

I bet I even know which component's causing it.

Graham

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.

 

[FunkyPunk FieldEffectTrollsistor]

100% correct. It'll almost certainly be a Y2 cap between the live and
secondary sides of the switching transformer.

Switcher front ends have transformers? Are you mixing your power
supply designs in your head, boy?

Go to powerint.com to find out why it's there.

Do the math on the cap and find out that even "fully charged" it will
not present the scenario she described. You are all fucking loony tunes
if you think it does.

 

[FunkyPunk FieldEffectTrollsistor]

YOU obviously haven't a clue what it is.

Graham

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 ****.