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Hobbyist Bench ground

  1. Jan 21, 2016 #1
    I'm trying to setup a hobbyist electronic bench in the garage. What is the best way to setup ground.
     
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  3. Jan 22, 2016 #2

    DrClaude

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    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 ?)
     
  4. Jan 22, 2016 #3

    CWatters

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    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.
     
  5. Jan 22, 2016 #4

    sophiecentaur

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    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 :smile:.
    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.
     
  6. Jan 22, 2016 #5

    Nidum

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    (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 .
     
    Last edited: Jan 22, 2016
  7. Jan 22, 2016 #6

    Nidum

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    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 .
     
  8. Jan 22, 2016 #7

    jim hardy

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    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
     
  9. Jan 22, 2016 #8

    sophiecentaur

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    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. :smile:
     
  10. Jan 22, 2016 #9

    DrClaude

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    Should've kept my mouth shut. But I did get the good idea to call you guys in :wink:
     
  11. Jan 22, 2016 #10

    sophiecentaur

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    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.
     
  12. Jan 22, 2016 #11

    Bystander

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    :oldconfused:
     
  13. Jan 22, 2016 #12

    sophiecentaur

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    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.
     
  14. Jan 22, 2016 #13
    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.
     
  15. Jan 22, 2016 #14

    jim hardy

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    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..

    200px-Philco_radio_model_PT44_front.jpg

    http://antiqueradio.org/safety.htm
    upload_2016-1-22_20-34-17.png
    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.
     
  16. Jan 23, 2016 #15

    sophiecentaur

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    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'!!!
     
  17. Jan 23, 2016 #16
    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.
     
  18. Jan 23, 2016 #17
    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.
     
  19. Jan 24, 2016 #18

    sophiecentaur

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    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:smile: too.
     
  20. Jan 24, 2016 #19
    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.
     
  21. Jan 24, 2016 #20

    meBigGuy

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    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.
     
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