Hobbyist Electronic Bench Ground Setup: Best Way

[Burntresistor]

I'm trying to setup a hobbyist electronic bench in the garage. What is the best way to setup ground.

 

[DrClaude]

As far as I know, connecting to a water pipe should work.

I'll let more knowledgeable people chime in (maybe @sophiecentaur or @jim hardy ?)

 

[CWatters]

Where I live the utility company supplies ground free with every two power you purchase :-) Otherwise your electrician installs an Earth rod. Water is delivered in plastic pipe.

 

[sophiecentaur]

As far as I know, connecting to a water pipe should work.

I'll let more knowledgeable people chime in (maybe @sophiecentaur or @jim hardy ?)

If you are in the UK, then I would say that the supply company's Earth would be a reliable place to start - and that will turn up in the mains supply to your (correctly wired)bench. That takes care of safety. Jim will know more about the problems in the US .
If you are after low EMI and Hum, then you may need to experiment when the equipment you are using starts to give trouble. Reducing hum can often involve actually cutting through ground leads, one at a time, until it goes away. But that's for a later date. A good RF Ground could be the bonded system (pipes etc) that connects to your mains earth.

 

[Nidum]

I'm trying to setup a hobbyist electronic bench in the garage. What is the best way to setup ground.

(1) Others have told you about power electrics grounding .

(2) Always a good idea to have RCD protection .

(3) For making experimental circuits with static sensitive components it is good practice to have an antistatic covering to your workbench and a wrist strap .

(4) Do you really mean grounding in the sense of electrical earthing ? - or are you actually asking what equipment you need to get started and how best to arrange bench layout ?

(5) Dust and damp are often a problem in garages . Need to eliminate both if possible or otherwise protect you equipment using covers and silica gel bags .

 

[Nidum]

On the subject of what equipment you need :

When I started off life was easy - you acquired meters , scopes , signal generators , power supplies , soldering irons et al as needed and as funds allowed .

You still need some things like soldering irons but there is now a choice to be made for the more sophisticated test and experimental equipment about whether to use a collection of individual devices or whether to go for a lab centre approach with everything based on one or more PC's .

Personally I use PC based systems a lot now .

Nostalgia again :

I started off using PC based test equipment about 35 years ago when I made an I/O board for my Apple-IIe . Lots of single bit I/O and some a/d d/a channels . Even with the seemingly impossibly low clock speed of the Apple and limitations of 6502 a viable digital test meter was developed .

My virtual scope worked but I couldn't get the bandwidth very high even with some imaginative sampling methods . OK for monitoring stepper motor signals though which was useful at the time .

Board was also used to control and monitor many experimental set ups . Used it professionally a few times as well .

 

[jim hardy]

I'm trying to setup a hobbyist electronic bench in the garage. What is the best way to setup ground.

I would use the third wire in the house wiring, usually green or bare, I'd Earth the bench to it by using a metal outlet box.

At your panel throw the breaker for the outlet you intend to use and verify with an ohmmeter that "ground"(I call it Earth) and Neutral are indeed connected together and read only an ohm or less.
That'll be the white and green slots as indicated here fro whatever outlet you have..
http://www.stayonline.com/reference-nema-straight-blade.aspx
Next, either install a GFCI breaker in that panel location
or install a GFCI outlet in your garage. Today's NEC requires that anyway.

What makes me nervous about using water pipes is this -
increasingly we see PVC in supply lines, which insulate the house plumbing from earth.
When a heating element inside the electric hot water heater cracks it connects the water inside those pipes to housepower ,
so you're relying on your hot water heater's earthing wire to keep everything safe
and the tank is probably glass lined
so a single piece of PVC pipe anyplace can cause mischielf
and i don't like to challenge such tenuous safety features.
We've had PF threads where people report shocks from their kitchen spigots - mostly from India i think
but I've seen it here in Arkansas... Lime buildup on the heating elements makes them overheat and crack. If you make yourself a homemade static wrist strap
be sure to put at least a megohm in series with it to limit current through your wrist. Proper ones I've seen have 10 megohms...

old jim

 

[sophiecentaur]

I would use the third wire in the house wiring, usually green or bare,

That gives me a cosy, safe feeling about the wiring you can find in UK houses. A BARE Earth conductor has not been permitted for decades over here.
Likewise about some of your other comments.

 

[DrClaude]

What makes me nervous about using water pipes is this -

Should've kept my mouth shut. But I did get the good idea to call you guys in

 

[sophiecentaur]

What makes me nervous about using water pipes is this -

The UK regs insist that all metalwork associated with plumbing or house structure has to be bonded to a common Ground and the company earth. That way, if a plumber disconnects one metal pipe from another, they will remain with zero PD between them. The bonding has to be with copper wire with green and yellow striped sleeving. God, they're obsessed with safety here.

 

[Bystander]

company earth

 

[sophiecentaur]

The third, armoured conductor (or fifth, when the supply is 3 Phase)) which comes on the cable from the supplier. There are some remote places where a local Earth spike is required but, afaik, that is also provided or supplied by the company before the supply is signed off.

 

[Burntresistor]

Thanks for the help. I'm setting a bench up with safety in mind. I'm worried about getting zapped. I was curious if connecting the bench to Earth would help that. I bought a Dc power supply and I have other standard equipment: 2 meters, soldering iron , Magnification lamp.

 

[jim hardy]

Myself i prefer a nonconductive benchtop. A metal bench with frame earthed is fine but the flat working surface i would make of wood or cover with carpet.
Why ?
Many table radios from 1940's to 1960's have the metal chassis connected to one side of the power cord.
So,
when the chassis is removed from the case for work,
it is easy to grab a handful of house power.
Setting such a chassis on an earthed metal surface can be an exciting event to witness.
That happened to a friend of mine - but only after he'd got false confidence built up. The non- polarized power cord would go into the socket either way and third time was the charm for him..

http://antiqueradio.org/safety.htm

See that L2 to Chassis connection ?
One must form the habit early of always checking first thing for continuity between power cord and chassis, and power cord to circuit common.

 

[sophiecentaur]

it is easy to grab a handful of house power.

Kamicaze hobbyist, I imagine!
My dad made me a two valve amp for my guitar. No case, of course. I was using it on my bed and went to lift it up by the most convenient part - the mains transformer - with my two thumbs pressing down on top. That was "the charm" for me. I got me 'really flustered'!

 

[Jeff Rosenbury]

For most work, simply tying into the house wiring (ground) is fine. From your equipment it doesn't look like you're doing anything exotic like high voltage or summoning the spirit of Edison like Jim does.

In low voltage electronics, good work habits are more important. Avoid wearing metal, keep a clean bench, work with one hand, keep a fire extinguisher handy, etc.

 

[Burntresistor]

This is close to the same topic(bench setup). So I didn't make a new thread. I found a affordable Oscope on amazon. What would you recommend to clip the negative part of the 10x probe. What kind of metal? Or if I'm wrong and I don't need anything for it to work.

 

[sophiecentaur]

I read and then lost a comment, in a post about Jim worshipping the Ancients of EE. I was going to post a 'like' on it and I'm sure Jim would have too.

 

[Jeff Rosenbury]

This is close to the same topic(bench setup). So I didn't make a new thread. I found a affordable Oscope on amazon. What would you recommend to clip the negative part of the 10x probe. What kind of metal? Or if I'm wrong and I don't need anything for it to work.

Grounding a probe is a touchy subject. How to do it changes with the frequency at which you work. It can range from just using your scope ground all the way to designing special test points.

In any case, standard wire (copper or whatever they are substituting these days.) should work. But remember the length of the loop between the probe tip and the ground clip adds inductance. At audio frequencies that's not much of a problem. For high speed electronics, it can be a show stopper.

 

[meBigGuy]

his is close to the same topic(bench setup). So I didn't make a new thread. I found a affordable Oscope on amazon. What would you recommend to clip the negative part of the 10x probe. What kind of metal? Or if I'm wrong and I don't need anything for it to work.

Not sure I entirely understand the question. Are you trying to replace a missing ground clip on a probe? Or just wondering where to clip it when you make measurements?

You DEFINITELY need a ground lead/clip, and generally it should be connected to ground on the device you are probing. As Jeff said, the length of the ground lead will have a significant effect on high speed signals (> 100MHz). 4 inches is a typical ground lead length for non-critical risetime measurements. When you are probing high speed signals you should take the probe tip off and ground directly to the barrel by whatever technique you can manage.

 

[Burntresistor]

Basically where I should clip it. Thanks for the help.

 

[meBigGuy]

You need to be a bit careful where you clip scope ground since the scope is likely grounded to the mains ground. If you accidently clip it to a power supply, for example, and the supply's ground is mains ground, then you will short the supply.

It's usually safe to clip scope ground to the system chassis, if there is a metal chassis. The chassis is not always the "most accurate" ground if you are making very sensitive measurements. Sometimes it makes sense to measure with a voltmeter between what you think is system ground and scope ground just to be sure you are not shorting something.

Sometimes I cheat and use a 3-2 adapter (in the US) to allow the scope chassis/ground to float, but you need to be very careful when doing so.

Every situation is different, and you need to proceed carefully.

 

[Planobilly]

I am assuming Earth ground is what you are asking about. I also work in my garage. I drove a 8 foot 1 inch copper rod into the ground and ran a 8 gauge copper wire to my bench. All my equipment is grounded through electrical system which uses the same sort of grounding set up. My idea was to have a good Earth ground that was not connected to the electrical system so as to get away from the line noise. I can run my scope on batt. power and use the ground ground connection I created.

I also have a Variac and an isolation transformer at hand. The work bench is wood which I cover at times with a static free mat. The floor is cement which I cover with a electrical insulation mat.

I work on high voltage electronics, so safety is a serious consideration for me.

Best of luck with the new set up!

Billy

 

[Boolean Boogey]

As someone that does electrical work for a living I do not advise using water pipes as a ground. There are reasons I don't like it but I will not go into them. I much prefer using the ground that is available in the walls.

Just, whatever you do DO NOT use a bootleg ground. Too many dummies like those.

I am assuming Earth ground is what you are asking about. I also work in my garage. I drove a 8 foot 1 inch copper rod into the ground and ran a 8 gauge copper wire to my bench.

I like this, assuming you put the ground rod at least 2 feet from the house and steer clear of underground utilities!

 

[Bystander]

DO NOT use a bootleg ground

 

[Boolean Boogey]

Sorry, do not use a neutral as a ground.

 

[jim hardy]

Thanks for adding that term to my vocabulary.

old jim

 

[Boolean Boogey]

Bootleg grounds are common in old houses and it's how 3 wire dryers were grounded. The danger is that if the neutral or receptacle is damaged whatever is grounded will be energized.

Bootleg grounds are illegal via the NEC but are common to find. I've been shocked by them so I am adamant that they're too risky and unsafe.

 

[Planobilly]

Another word about grounding...something I learned when I was living in Arizona. The ground was so dry in Arizona that a 8 foot ground rod that would work well here in Florida would not work well there. In fact, when I was building my shop there, the inspector ask me to connect all the steel in the slab and use two 8 foot rods spaced a certain distance apart and even then the ground was not very good. Point being, there is more to grounding than one would expect.

Here is a PDF that will tell you most everything you want to know and a bunch of stuff you most likely never wanted to know...lol The good news is there are a lot of pictures in the PDF. This is out of the National Electrical Code here in the United States. I assume electrical codes will be some what different in Europe and other parts of the world but in general the system here is pretty safe.

http://fyi.uwex.edu/mrec/files/2011/04/W4.-Biesterveld-NEC-grounding-MREC2010.pdf

As I stated in my first post, I installed the ground rod with more reasons that just safety in mind. The ground rod I installed is several feet from the house and away from other metal and electrical wire. I placed it in that location to prevent as much noise as I could. I don't have in mind to live forever but I can think of several places better than my garage to die in! A good safe and well though out grounding system that meets your need is well worth the effort to install.

In this life, there is no way to make anything 100% safe but one can and must manage the risk involved.

Cheers,

Billy

 

[jim hardy]

If one is protecting against shocks from utility power

Kirchoff tells us that any current beginning at our utility transformer will do its best to get back to that transformer.
That transformer's center tap is its 0v reference point and is, in US, connected to Earth .
On a pole mounted transformer it's 'earthed' by this bare copper wire coming down side of the pole. The bare wire is coiled on the bottom of the pole to have max surface area contacting earth.
In my neighborhood it also goes on up to very top of the pole where it serves as a small lightning rod.

from http://www.science.smith.edu/~jcardell/Courses/EGR220/ElecPwr_HSW.html , a pretty good link.

Your household 'grounding' conductor is also tied to it by the third bare wire coming in from the transformer.

So the household ground system is good at protecting you from utility power. That's why i'd use it for my bench.

Something interesting happened to me once
i was using my new metal cased electric drill , properly connected to Earth by its third prong and my household ground system.
Out of the blue lightning struck my utility pole.
I found myself with a double handful of drill solidly wired to the bottom of a lightning bolt. Path was: Drill case to third prong to green wire in the conduit to bonding point in my panel to bare incoming wire from pole to bare copper wire on side of pole, top of pole was immersed in a big fat brilliant white lightning bolt.
KVL flashed immediately through my mind.
No pun intended, but I sure saw the light !
Voltage between my feet and hands was same as voltage drop along the Earth from bottom of the power pole to where i was standing , while the lightning bolt dumped its considerable Coulombs into the Earth and they dissipated. That took about a half second, . I consider myself lucky to be here to tell that tale...

If you live in a lightning prone area - stay away from "grounds" during thunderstorms. Your "grounded" bench is really "grounded" at your ground rods , which can get tangled up with lightning as happened to me.

That voltage drop along Earth when it's conducting is called "Step Potential", volts per average man's stride of about a yard.
We design switchyards to keep it low enough to not electrocute a man should a nearby high voltage wire fall to the ground.

My newer drills are all "Double Insulated" ...

old jim