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I need to setup an anti-static workbench in my spare office, and kids sometimes get into it ever since they learned how to pick the locks.

My intended approach is to:

  1. Lay out an ESD mat on the desk.
  2. Punch a whole through the mat, and connect an ESD common point ground to the mat through the whole with a snap-cap.
  3. Connect my ESD wrist strap by removing the alligator clip and connecting the wrist strap to the common point ground.
  4. Connect the banana jack of the common point ground to the GND pin on the NEMA-5-15 wall outlet or equivalent on the power bar on my desk, ie:

NEMA-5-15 Outlet

I have one problem with this setup, assuming it is correct: I have a small, flat nema-jack connected to the GND of the wall outlet with an exposed banana plug sticking out of the wall. I'm worried that one of the kids could pull the banana plug out of the GND plug, and plug the banana jack into the hot or neutral blade slots of the wall outlet.

Is there a safer way to go about this? Are there maybe 3-prong plugs that have two plastic blades for the neutral and hot, and a fixed metal plug for the GND so there's no way someone can electrocute themselves by playing with the connector to the mat?

JYelton
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Cloud
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  • I'd go for a better lock – Scott Seidman Oct 09 '14 at 23:19
  • @ScottSeidman I'd like to go that route, but they're just the simple single-hole locks that you can open with a stiff paperclip. I don't want anyone able to lock themselves in a room. – Cloud Oct 10 '14 at 02:21

3 Answers3

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Get yourself one of these guys, and wire your ground into it. For good measure, double insulate the hot and neutral lugs inside the plug.

enter image description here

The worst the kids will be able to do is unplug it, and they're less than $10 at most places electrical products are sold.

Matt Young
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This is what you're looking for.

Anti-static grounding plug

Assuming the same thing is available in your local plug style, and your house grounds are correctly wired.

Community
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  • I've never seen such an animal before, definitely going to put one on the next supply order. – Matt Young Oct 09 '14 at 19:59
  • Do you know where I can find any in a NEMA5-15 form factor for North American (Canadian) outlets? That's awesome! – Cloud Oct 10 '14 at 02:20
  • Humph. This is weird. Looked at Newark (the American portal of Farnell) and they only stock these in Schuko (European) and BS1343 (UK). Perhaps they aren't available in US style (NEMA?) Only reason I could imagine would be the difficulty of making insulating prongs that thin - unless there's a bizarre regulatory reason. Anyone know? –  Oct 10 '14 at 09:34
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The metal screws in the plug's wall plate are also grounded. Make sure the grounding wire has at least 1M ohm resistance between the common grounding point on the mat and the end of the wire, terminate the wire in a ring terminal, and screw the ring terminal to the screw in the wall plate. You can confirm grounding with a multimeter, but as long as the outlet is grounded, all metal parts, including the screw, accessable to the user must be grounded.

This has worked very well for me for years - it doesn't tie up the outlets, nor does it get unplugged easily and left off.

Note that the common ground point (item 2 in your list) is already terminated in a ring terminal, so you shouldn't have to modify it at all.

Adam Davis
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