static grounding question

notahardwareguy · Jun 2, 2011

I hobbied with electronics when I was much, much younger and am getting back into it with a kit build and then a laser build. When I did this before, I had copper pipes in the house that I would ground myself to. Today, PVC only, no exposed copper pipes, no register heat, no nothing! What else can I ground myself to so as to not destroy my diode? Would the ground plug of an AC outlet work? Other suggestions?

I did a forum search and did not see this questions asked so here it is and sorry if it has already been posted and answered.

Thanks.

Lotus_Darkrose · Jun 2, 2011

Pretty sure if you were that concerned about the static you could just use an anti-static wristband and attach it to something large and metal. Just like when you work on a computer. Anything more than that seems overboard to me.

notahardwareguy · Jun 2, 2011

Well that is my question, what would/could I attach a wrist strap to? When I work on computers, I attach the wrist strap to the computer, turn it off but leave it plugged into the outlet.

In this case, the room I will be using has no computer or other large electrical equipment in it. It has a tile floor on a concrete slab.

My options? Thanks.

lasersbee · Jun 2, 2011

Any electrical device plugged into the house current with
a 3 pin plug is automatically grounded...

In the shop we use a banana plug on a wire and hook right
into the 3rd Ground pin of the shop wall receptacle.

BEFORE you do this you must check that your house wiring
was done properly and that in fact the 3rd pin is actually
a good ground..

Jerry

notahardwareguy · Jun 2, 2011

That thought occurred to me, to use the ground plug of a wall outlet so thanks for confirming that.

What is the best way to check (at the outlet) if it is wired correctly? I have a volt meter. Thanks.

lasersbee · Jun 2, 2011

A three prong receptacle will have...

1- round ground hole
1- shorter slot
1- longer slot

Between the shorter slot and the longer slot you should
have ~125VAC..

Between the round Ground hole and the shorter slot
you should have ~125VAC..

Between the round Ground hole and the longer slot
you should have 0.0VAC....

Jerry

notahardwareguy · Jun 2, 2011

:yh: Fantastic and thanks much!

Will check when I get home. If that is the case, I will make up a plug with terminated tines and a connector for the ground post with which to connect my static strap to.

lasersbee · Jun 2, 2011

And for Gods sake... only use it on the same exact wall receptacle
that you tested... any other receptacle could still be wrongly
wired...

Jerry

Lotus_Darkrose · Jun 2, 2011

It definitely makes sense that Jerry does this at his shop. Those pictures of his work area he posted had TONS of electronics all over. Definitely need to step up precautions when you have that many electronic components all over the place.

Benm · Jun 3, 2011

One word of warning on grounding using mains ground: This is okay, but make sure to use a wristwrap with builtin resistor (most of them do), or otherwise provide a resistor between ground and yourself.

This is because in case of a short between live and ground it some other device connected to mains, the ground wire can be lifted from ground potential quite a bit before a fuse breaks the circuit.

Brenner · Jun 3, 2011

If you do not want to destroy your diode by ESD, > short the leads... simple as that..
Once you are done with soldering to your driver PCB , remove short "device" (usually piece of wire). When not in use you can keep diode in conductive foam.

Cheers

Benm · Jun 3, 2011

Shorting the leads can be effective, but on case-neutral diodes like the 445s its not a guarantee either since you can have ESD between the die and case even if both leads are shorted to eachother but not to the case.

I've never left a shorting wire in place while fitting a driver, but as a precaution during shipping its a good idea. Inserting the diode in a bit of antistatic foam and warpping the hole thing in tinfoil seems like the most convenient way though.

Brenner · Jun 3, 2011

No protection is 100% safe when working with ESD sensitive devices. I mentioned one “on the fly” quick solution.

If we are going pro then:

1. ESD wrist strap (MUST have), or if you move around a lot > ESD Heel grounders
2. ESD floor mat or Conductive Table Top Mat
3. Constant monitor (gives you visual and sound alert if you are not grounded)
4. All ESD sensitive (through hole) components MUST be shipped in a conductive foam, then wrapped in ESD safe packaging. It is a little bit different story when talking about SMD components.

El. professionals in USA mostly use 3M ESD safety products.

grenadier · Jun 3, 2011

Honestly, the only things that I have been able to damage with static were RF power transistors (> 300MHz). Laser diodes, mosfets, digital ICs (even 3.3V cmos) are quite tough to kill with esd. In fact chip manufacturers now put esd protection in their ICs (basically zener diodes) to make them even static proof.

In the 70s static electricity was a big problem for semiconductors. Now, not so much. Semiconductor manufacturing has improved to the point where ESD is actually of little concern for most components, yet people don't change their ways.

Brenner · Jun 3, 2011

It really depends on many factors in your working environment

: level of room air humidity, flooring, clothing you wear, ...

It is your personal choice to play with your $40-$50 laser diode w/o ESD protection.

I hope you were joking...

Just to remind you:

Human body can generate static as high as 15000 V

Coherent Light · Jun 3, 2011

Get a clean room wireless static wrist strap ~$25.00 they really do work. I have been using one for about 3 months now with absolutely no issues with static.

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