Author Topic: Workbench electrical safety advice  (Read 7255 times)

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Offline l9oTopic starter

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Workbench electrical safety advice
« on: December 16, 2022, 03:44:51 pm »
I'm currently setting up a workshop with a workbench for developing, debugging and reverse engineering electronics. Pretty standard stuff: an oscilloscope, power supply, function generator, etc.

I have an electrician redoing my basement electrical, so this feels like a good time to think about safety of my workshop.

What is some advice you would give to someone who is setting up a bench from scratch? Do I need GFCI outlets? An AFCI breaker? Something I should do to ground my workbench? Anything else?

Currently I have planned:

1. A separate 20A breaker for the workshop area, shared between lights and all the outlets in the room
2. On top of the workbench, 4 outlets: so I can plug in DUTs and other temporary devices like soldering iron. I might add a wall switch for these 4 outlets, just for peace of mind.
3. On the bottom of the workbench, 2 outlets: so I can leave a few instrumentation devices plugged in all the time (mostly power supply and oscilloscope)
4. On another corner of the workshop I also have outlets for computer, etc - though I don't expect those to be using DUTs all that often

For context, I'm a Software Engineer who likes to play with electronics and radio/SDR, so mostly low voltage stuff. I would imagine I want to protect myself and my gear from ground loops, issues with scope grounding and accidental fuck ups I might do with the DUTs like shorts.

If there are any EEVBlog videos or other material that you find useful, feel free to send my way - I tried searching for this but mostly just found material about electrical safety in general, not a whole lot of advice for an electronics lab. Would be glad to get recommendations of any products as well.
 

Online themadhippy

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Re: Workbench electrical safety advice
« Reply #1 on: December 16, 2022, 04:02:16 pm »
Quote
A separate 20A breaker for the workshop area, shared between lights and all the outlets in the room
might want to consider putting the lights on a different circuit to your bench supply,that way when something goes bang your not plunged into darkness.
 
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Offline rstofer

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Re: Workbench electrical safety advice
« Reply #2 on: December 16, 2022, 04:45:31 pm »
What is some advice you would give to someone who is setting up a bench from scratch? Do I need GFCI outlets? An AFCI breaker? Something I should do to ground my workbench? Anything else?

There are outlets which combine both AFCI and GFCI features.  I would use them...
 
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Offline Brianf

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Re: Workbench electrical safety advice
« Reply #3 on: December 16, 2022, 04:55:32 pm »
You don't have enough outlets. My workshop (well the one I'm in now) has 16 of them easily accessible for occasional kit, soldering irons, and similar. Then there's the two 9-way strips behind the test equipment shelf. There are then another 12 under the PC bench for PC stuff.
« Last Edit: December 16, 2022, 04:57:47 pm by Brianf »
 
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Offline rstofer

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Re: Workbench electrical safety advice
« Reply #4 on: December 16, 2022, 04:57:36 pm »
I would mount a long multi-outlet strip to the bench or to the wall behind the bench.  You can't have too many outlets.  I might put one down low and one at the table top.

You really can't have too many outlets.  Most strips have the outlets so close together that a wall-wart uses up 2 or 3 spaces so right away you have less outlets than you bought.  I get around the problem with short extension cords:

https://www.amazon.com/dp/B09Y1SXW3J


 
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Offline l9oTopic starter

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Re: Workbench electrical safety advice
« Reply #5 on: December 16, 2022, 05:28:12 pm »
You don't have enough outlets. My workshop (well the one I'm in now) has 16 of them easily accessible for occasional kit, soldering irons, and similar. Then there's the two 9-way strips behind the test equipment shelf. There are then another 12 under the PC bench for PC stuff.

Oh yeah, I was planning on just using strips to complement those. Is that a bad idea?
 

Offline AVGresponding

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Re: Workbench electrical safety advice
« Reply #6 on: December 16, 2022, 05:33:05 pm »
Something I should do to ground my workbench? Anything else?

Get a good sized anti-static mat. I would not recommend grounding the bench, as there's a fair chance of you being the path to earth between the DUT and bench at some point. I would not use a metal workbench at all, for this reason. Wood is much better, and more pleasant to the touch too.
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Offline tooki

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Re: Workbench electrical safety advice
« Reply #7 on: December 16, 2022, 06:25:29 pm »
You don't have enough outlets. My workshop (well the one I'm in now) has 16 of them easily accessible for occasional kit, soldering irons, and similar. Then there's the two 9-way strips behind the test equipment shelf. There are then another 12 under the PC bench for PC stuff.

Oh yeah, I was planning on just using strips to complement those. Is that a bad idea?
Yes, power strips are always inferior to real outlets. This is exactly the moment to equip yourself with enough outlets so you don’t have to mess with power strips.
 

Offline nightfire

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Re: Workbench electrical safety advice
« Reply #8 on: December 17, 2022, 12:40:01 am »
Some RCD in front of your outlets are mandatory- in my case I put a PRCD in front of a 19" server rack power outlet strip and plugged that into my wall outlet that has no RCD because my apartment is older than RCDs becoming mandatory for every outlet in the house.

Depnding on the code in your area, solutions (GFCI etc.) will probably vary.

I also would use whether some isolating wood bench, or put grounding on metal parts.
Also: provisions for connecting to antistatic measurements like wrist strap and central connecting point for that.
 

Online nctnico

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Re: Workbench electrical safety advice
« Reply #9 on: December 17, 2022, 12:48:54 am »
You don't have enough outlets. My workshop (well the one I'm in now) has 16 of them easily accessible for occasional kit, soldering irons, and similar. Then there's the two 9-way strips behind the test equipment shelf. There are then another 12 under the PC bench for PC stuff.

Oh yeah, I was planning on just using strips to complement those. Is that a bad idea?
Yes, power strips are always inferior to real outlets. This is exactly the moment to equip yourself with enough outlets so you don’t have to mess with power strips.
That is impossible. You need about 20 outlets per meter of bench space. Good quality power strips (fixed to the underside of the desk for example) will do that. Regular outlets not so much; they physically won't fit and you need excessive daisy-chaining.
« Last Edit: December 17, 2022, 12:53:08 am by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online themadhippy

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Re: Workbench electrical safety advice
« Reply #10 on: December 17, 2022, 01:08:19 am »
In the uk at least,the advantage of using proper sockets instead of power strips is  power bars  often  have a fuse fitted,so thats  a fuse in the plug powering the power bar ,a fuse in the power bar and another on the plug  feeding the bit of kit,now which ones blown?
 

Offline EPAIII

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Re: Workbench electrical safety advice
« Reply #11 on: December 17, 2022, 08:28:36 am »
I will add to the grounded workbench idea. In over 45 years of work in electronics and at least 15 additional ones where it has been a hobby, I have only been shocked twice. The second and worse time was about 40,000 Volts DC that passed through a probe I was holding (not a HV probe), through my hand, out my foot, through my shoe, and into the grounded, metal bench I was working at.

My present electronic benches are wood and wood top with a metal frame below. Neither one is grounded.

As for anti-static mats, I have worked with and without them. I saw ZERO difference. Perhaps if you find that static discharge is a problem for you, then get one. But I see no reason otherwise. Not having a carpet on the floor is probably a better anti-static protection than those mats ever will be.



You don't have enough outlets. My workshop (well the one I'm in now) has 16 of them easily accessible for occasional kit, soldering irons, and similar. Then there's the two 9-way strips behind the test equipment shelf. There are then another 12 under the PC bench for PC stuff.

Oh yeah, I was planning on just using strips to complement those. Is that a bad idea?
Yes, power strips are always inferior to real outlets. This is exactly the moment to equip yourself with enough outlets so you don’t have to mess with power strips.
Paul A.  -   SE Texas
And if you look REAL close at an analog signal,
You will find that it has discrete steps.
 

Offline EPAIII

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Re: Workbench electrical safety advice
« Reply #12 on: December 17, 2022, 08:39:07 am »
If you buy your power strips at WalMart, yes they well be inferior.

Every professional shop I have built has been equiped with the Wiremold, Plugmold strips. I also specified them for professional rack installations. They are better than all but the best, high end, most expensive outlets. I never had a single problem with them. I always got the ones with an outlet every six inches. If you don't specify that, the electrician will go cheap with the ones with them only every ten or twelve inches. Then they curse like hell when you make them take them back out and install the right ones.



You don't have enough outlets. My workshop (well the one I'm in now) has 16 of them easily accessible for occasional kit, soldering irons, and similar. Then there's the two 9-way strips behind the test equipment shelf. There are then another 12 under the PC bench for PC stuff.

Oh yeah, I was planning on just using strips to complement those. Is that a bad idea?
Yes, power strips are always inferior to real outlets. This is exactly the moment to equip yourself with enough outlets so you don’t have to mess with power strips.
Paul A.  -   SE Texas
And if you look REAL close at an analog signal,
You will find that it has discrete steps.
 
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Online nctnico

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Re: Workbench electrical safety advice
« Reply #13 on: December 17, 2022, 11:07:21 am »
In the uk at least,the advantage of using proper sockets instead of power strips is  power bars  often  have a fuse fitted,so thats  a fuse in the plug powering the power bar ,a fuse in the power bar and another on the plug  feeding the bit of kit,now which ones blown?
Is that actually useful? IMHO that is more like a UK 'thing'. Having fuses everywhere means introducing places where you can have contact problems and increased costs. All AC powered equipment has fuses inside it already. In the past 20 years I only tripped a breaker once and that way because a big ass power supply wasn't completely set to 230VAC (it had another hidden voltage selection strap). The fuse was sized for 110V operation so it had a higher rating than the mains breaker.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Sherlock Holmes

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Re: Workbench electrical safety advice
« Reply #14 on: December 17, 2022, 11:24:43 am »
I'm currently setting up a workshop with a workbench for developing, debugging and reverse engineering electronics. Pretty standard stuff: an oscilloscope, power supply, function generator, etc.

I have an electrician redoing my basement electrical, so this feels like a good time to think about safety of my workshop.

What is some advice you would give to someone who is setting up a bench from scratch? Do I need GFCI outlets? An AFCI breaker? Something I should do to ground my workbench? Anything else?

Currently I have planned:

1. A separate 20A breaker for the workshop area, shared between lights and all the outlets in the room
2. On top of the workbench, 4 outlets: so I can plug in DUTs and other temporary devices like soldering iron. I might add a wall switch for these 4 outlets, just for peace of mind.
3. On the bottom of the workbench, 2 outlets: so I can leave a few instrumentation devices plugged in all the time (mostly power supply and oscilloscope)
4. On another corner of the workshop I also have outlets for computer, etc - though I don't expect those to be using DUTs all that often

For context, I'm a Software Engineer who likes to play with electronics and radio/SDR, so mostly low voltage stuff. I would imagine I want to protect myself and my gear from ground loops, issues with scope grounding and accidental fuck ups I might do with the DUTs like shorts.

If there are any EEVBlog videos or other material that you find useful, feel free to send my way - I tried searching for this but mostly just found material about electrical safety in general, not a whole lot of advice for an electronics lab. Would be glad to get recommendations of any products as well.

Shame you can't get switched power outlets in US. In UK one can cut power just by switching the outlet off, here in US you must pull it out, very kludgy.
“When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.” ~ Arthur Conan Doyle, The Case-Book of Sherlock Holmes
 

Offline tooki

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Re: Workbench electrical safety advice
« Reply #15 on: December 17, 2022, 01:39:26 pm »
If you buy your power strips at WalMart, yes they well be inferior.

Every professional shop I have built has been equiped with the Wiremold, Plugmold strips. I also specified them for professional rack installations. They are better than all but the best, high end, most expensive outlets. I never had a single problem with them. I always got the ones with an outlet every six inches. If you don't specify that, the electrician will go cheap with the ones with them only every ten or twelve inches. Then they curse like hell when you make them take them back out and install the right ones.
Those are a great solution, and as hard-wired items, fall under the “real outlets” I meant.

But yeah, when someone says “power strip”, they generally mean the wal-mart kind… :(
 

Offline Monkeh

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Offline tooki

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Re: Workbench electrical safety advice
« Reply #17 on: December 17, 2022, 01:44:30 pm »
As for anti-static mats, I have worked with and without them. I saw ZERO difference. Perhaps if you find that static discharge is a problem for you, then get one. But I see no reason otherwise. Not having a carpet on the floor is probably a better anti-static protection than those mats ever will be.
The big problem with the “I’ve never had ESD damage before” is that you don’t actually know that; a lot of ESD damage is not such that it causes immediate, complete failure, and the discharges sufficient to damage sensitive electronics are far smaller than anything we can see or feel. Often, a discharge just degrades a part, such that it no longer performs to spec, or damages it in a way that it fails down the line (and then we attribute the failure to random failure or age, and not the causative ESD event).

ESD mats are cheap, and a great way to protect the workbench anyway, so IMHO there’s no excuse to not have one.
 

Offline tooki

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Re: Workbench electrical safety advice
« Reply #18 on: December 17, 2022, 02:08:31 pm »
That is impossible.
Oh?
Why can’t you have an electrician install as many as you need?

You need about 20 outlets per meter of bench space.
Says who?

Good quality power strips (fixed to the underside of the desk for example) will do that.
Sure, but why do that when you could have real, hard-wired outlets?

Regular outlets not so much; they physically won't fit
A 10-gang US electrical box is about 22” (around 60cm) wide, and that would fit 20 outlets.

and you need excessive daisy-chaining.
American outlets are designed for daisy-chaining, and hard-wired daisy chains are certainly preferable to plugged ones.
 

Offline Brianf

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Re: Workbench electrical safety advice
« Reply #19 on: December 17, 2022, 02:42:42 pm »
I use power strips designed for use in server racks.
 
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Offline AndyBeez

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Re: Workbench electrical safety advice
« Reply #20 on: December 17, 2022, 03:01:29 pm »
What about ventillation? Are you going to have an extractor fan with conduit to pull the solder fumes etc out of your man cave?
 

Offline aduinstat

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Re: Workbench electrical safety advice
« Reply #21 on: December 17, 2022, 03:05:03 pm »
As for anti-static mats, I have worked with and without them. I saw ZERO difference. Perhaps if you find that static discharge is a problem for you, then get one. But I see no reason otherwise. Not having a carpet on the floor is probably a better anti-static protection than those mats ever will be.
The big problem with the “I’ve never had ESD damage before” is that you don’t actually know that; a lot of ESD damage is not such that it causes immediate, complete failure, and the discharges sufficient to damage sensitive electronics are far smaller than anything we can see or feel. Often, a discharge just degrades a part, such that it no longer performs to spec, or damages it in a way that it fails down the line (and then we attribute the failure to random failure or age, and not the causative ESD event).

ESD mats are cheap, and a great way to protect the workbench anyway, so IMHO there’s no excuse to not have one.
I have had ESD damage before, and let me tell you, it is a wonderful feeling when your devices suddenly start working after the ESD mat is installed. I also recommend an ESD chair (even if it is not grounded), because chairs are probably the number 1 source of ESD, and an ESD chair cannot build a charge.

BTW, the reset pin on Atmel microcontrollers do not have ESD protection and are easy to blow.
« Last Edit: December 17, 2022, 03:26:00 pm by aduinstat »
 
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Online nctnico

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Re: Workbench electrical safety advice
« Reply #22 on: December 17, 2022, 06:12:52 pm »
As for anti-static mats, I have worked with and without them. I saw ZERO difference. Perhaps if you find that static discharge is a problem for you, then get one. But I see no reason otherwise. Not having a carpet on the floor is probably a better anti-static protection than those mats ever will be.
The big problem with the “I’ve never had ESD damage before” is that you don’t actually know that; a lot of ESD damage is not such that it causes immediate, complete failure, and the discharges sufficient to damage sensitive electronics are far smaller than anything we can see or feel. Often, a discharge just degrades a part, such that it no longer performs to spec, or damages it in a way that it fails down the line (and then we attribute the failure to random failure or age, and not the causative ESD event).

ESD mats are cheap, and a great way to protect the workbench anyway, so IMHO there’s no excuse to not have one.
I have had ESD damage before, and let me tell you, it is a wonderful feeling when your devices suddenly start working after the ESD mat is installed. I also recommend an ESD chair (even if it is not grounded), because chairs are probably the number 1 source of ESD, and an ESD chair cannot build a charge.
I agree about getting an anti-static mat. And if you work on customer products, get a wrist strap as well. I won't touch anything that goes out to a customer without wearing an anti-static wrist strap (and work on an anti-static mat). I learned about damage due to static discharge the hard way a couple of decades ago. I have a couple of these from a reputable brand:

« Last Edit: December 17, 2022, 06:14:59 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online nctnico

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Re: Workbench electrical safety advice
« Reply #23 on: December 17, 2022, 06:23:06 pm »
That is impossible.
Oh?
Why can’t you have an electrician install as many as you need?

You need about 20 outlets per meter of bench space.
Says who?

Good quality power strips (fixed to the underside of the desk for example) will do that.
Sure, but why do that when you could have real, hard-wired outlets?

Regular outlets not so much; they physically won't fit
A 10-gang US electrical box is about 22” (around 60cm) wide, and that would fit 20 outlets.

and you need excessive daisy-chaining.
American outlets are designed for daisy-chaining, and hard-wired daisy chains are certainly preferable to plugged ones.
20 outlets in 60cm would mean they are 3cm apart. Then you won't be able to fit a wall-wart in. And daisy chaining outlets isn't a very good idea because you create a connection at every point (worse when the outlets have push-in contacts). What I have done in my lab is to have use a star like distribution. There are two mains busses (on seperate circuits) running under my bench which feed a bunch of outlets (as branches from the bus). Those busses are connected using twist-on wire connectors instead of spring loaded connectors for improved reliability under high loads. From those outlets, a whole bunch of power strips are supplied (a total of 110 outlets for about 6 meters of bench / desk). That gives the least number of connections between the grid connection and outlets.
« Last Edit: December 17, 2022, 06:30:03 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Monkeh

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Re: Workbench electrical safety advice
« Reply #24 on: December 17, 2022, 08:33:18 pm »
And daisy chaining outlets isn't a very good idea because you create a connection at every point

This is how nearly every lighting and socket circuit throughout the world is wired. Hell, this is how every street light and house is wired under or over the road. You're overthinking things.
 


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