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Max The Magnificent
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Re: Maybe...
Max The Magnificent   8/14/2014 10:14:38 AM
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@David: ...The best solution would be to get a mains cable with a proper 3-pin plug,  cut the...

This is what I was planning on doing (except using plugs that are designed for you to wire up yourself) until Wnderer suggested using the existing banana plugs on the wristbands/mats along with these $7 ground plug adapters.

Max The Magnificent
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Re: power strip and ground plug adapter
Max The Magnificent   8/14/2014 10:11:52 AM
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@Wnderer: Get a powerstrip and one of these $7 ground plug adapters.

This is obviously the way to go -- I'm going to order the adapters right now -- Max

Wnderer
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Re: power strip and ground plug adapter
Wnderer   8/13/2014 7:46:03 PM
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@David Ashton Great little gadget, much easier than my idea if you can get them easily.


Digikey has them.

 

 

David Ashton
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Re: power strip and ground plug adapter
David Ashton   8/13/2014 6:17:14 PM
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@Wnderer....sorry, only noticed this post after I posted mine above.  Great little gadget, much easier than my idea if you can get them easily.

David Ashton
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Re: Maybe...
David Ashton   8/13/2014 6:14:31 PM
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@Max...sorry to rain on your parade (or pee on your fire) but I would say 100% of all the brick type laptop and other power supplies I have ever taken apart (and there have been a few) have been switching types with the output isolated from the mains.

A mini-tower desktop computer might be different - those power supplies usually have a connection between the mains earth and the case of the PC....but I am not sure whether this will extend to the USB shield, I will check mine when I can.

Your solution might be to just switch your power supply off rather than unplugging it.  Of course you should also check if the power supply ground goes all the way through to the output.

The best solution would be to get a mains cable with a proper 3-pin plug,  cut the IEC end off (preferably while it is NOT plugged in :-), strip it back a bit, and cut off and insulate the white and black wires (which is what I think you have in the US) leaving the green earth wire only - and connect that to your anti-static mat.  This does assume you have a spare power outlet where you are working, and that G the G does not want to use said outlet while you are electronicking...

PS to avoid the white and black wires shorting, cut them off different lengths.  Then get some pliers and pull the insulation so you don't have wire ends sticking out.  Then insulate them with tape.   As the Irish would say....To be sure...to be sure...

Max The Magnificent
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Re: Braided shield
Max The Magnificent   8/13/2014 5:41:37 PM
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@MeasurementBlues: Congratulations Max, you've just created a pigtail, a wonderful source of radiated emissions.

Thank-you-very-much ... I'll be playing here all week :-)

MeasurementBlues
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Google has found you
MeasurementBlues   8/13/2014 5:36:17 PM
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@Max, I get a Google alert for "electrostatic discharge" and you've been picked up.

MeasurementBlues
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Braided shield
MeasurementBlues   8/13/2014 5:30:59 PM
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Congratulations Max, you've just created a pigtail, a wonderful source of radiated emissions.

I'll be posting an article to my EDN blog about how those pigtails are evil.

The braided shielding -- shown pulled back from the inner wires, twisted together, and sticking out of the right-hand side



MeasurementBlues
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Re: Wear the wristband
MeasurementBlues   8/13/2014 5:26:26 PM
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As you surely know, never ever float the scope.

zeeglen
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Re: Wear the wristband
zeeglen   8/13/2014 5:24:09 PM
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@Martin So if your circuit is floating and you're connected to the low side of its power supply, you should be OK.

Also a good idea to connect a scope probe ground to a floating circuit as the first connection so that the circuit is no longer floating.  I've zapped MOSFETs by connecting the probe tip to the gate first before the ground.

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