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Grounding Question — Parallax Forums

Grounding Question

WhitWhit Posts: 4,191
edited 2009-01-11 13:44 in Robotics
Hey Everyone,

On another thread, we were talking about adding a ground on a rolling robot to dissipate static electricity. I assumed the wire under Ken's Hybrid was for this purpose (see picture). He says that it was not. So, I assumed wrong.

attachment.php?attachmentid=57877

But, I know I had read about or seen this somewhere.

So I started looking for where I might have read this. I found this (which was one place I remembered reading it).

Please take a look at - http://books.google.com/books?id=oqI5WC8M8qEC&pg=PA70&lpg=PA70&dq=Robot+%22grounding%22+%2B+Static&source=bl&ots=YF426ZBpGj&sig=c1Jdx9rVoJVuIL82UBt9NwWtD6M&hl=en&sa=X&oi=book_result&resnum=2&ct=result

I also know that I have seen it in pictures elsewhere too. Is any one doing this? Is it overly cautious.·I would love to hear·your thoughts on this. Is this necessary?

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Post Edited (Whit) : 1/9/2009 7:39:56 PM GMT

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-01-09 20:17
    Whit,

    In many manufacturing facilities roll around carts and shelf units will have a small chain hanging down for this purpose. I have even seen a forklift with a ground chain. All of these have been in special warehouses or manufacturing floors where the floor itself is coated with conductive paint. In some places the employees wear special garments and/or foot straps and often have to touch a sensor to be sure they are properly grounded. I don’t think I have seen a robot with one though. The wire in Ken’s photo, if memory serves, is just a disconnected wire from one of the HB-25 modules which had to be replaced during the early design. I remember Ken had a thread explaining his accident with the alternator and current issues. Take care.

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    Chris Savage
    Parallax Engineering
  • Ken GraceyKen Gracey Posts: 7,392
    edited 2009-01-09 20:30
    Hey Whit+

    Now I understand the concern you have posed.

    I just read the link you provided. Very interesting. In the all-metal robot that you're showing above, I confirm that the grounds are all connected together and bolted to the chassis. The concept of a dragging chain or wire that connects the robot to earth ground is interesting, but I don't think it's very necessary. The black wire you're seeing in my robot is a motor lead that I hadn't yet connected to an HB-25 motor controller.

    One issue with a metal chassis is that a short to the chassis could really destroy some electronics. Anything else connected to the chassis could be vulnerable. This isn't going to happen with wood, which is one reason why lately I've been acting like plywood is some kind of medical discovery for robotics.

    Maybe you should do what Aristides does in our office. Ari carries around black ESD foam (the kind your BS2s are plugged into). Everytime he touches a door or metal object he discharges it to the foam. Initially I thought this was some kind of temporary behavior, but now he's been doing it for the seven years I've known him. Maybe you could do the same with your robot.

    Remember though, I'm more of a hacker than engineer. I experiment first and understand later, all too oft. Get more opinions for certain.

    Ken Gracey
    Parallax, Inc.
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2009-01-09 20:39
    I've only seen a ground wire purposely designed into one of the early personal robots. The old Arctec Gemini robot used a length of metal bead chain (similar to the ones used as a pull chain on a lamp) that would drag along the ground to help dissipate any built-up static charge. I think it was more of a precaution since that robot used early CMOS which was highly sensitive to static discharge which could easily destroy some of the logic IC's. I'm not aware of any others that used one.

    Robert
  • WhitWhit Posts: 4,191
    edited 2009-01-09 21:28
    @Ken,

    I feel better now! At first I thought I had lost my mind. I agree with a wood of non conductive chassis, there is less to worry about.

    @Robert,

    Thanks for the info. I knew I had seen that people did this.

    @all,

    I guess once you move from BOE-Bots and Scribblers and little BEAM bots - you have to loose your mind for a bit. Making the mid-size bot with the 12 volt system, has me questioning everything. There are new components and complexities that I've never dealt with. Throw in trying to move to the Propeller. The budget is up too, so I don't want to make any easily avoidable mistakes. Thanks for listening to and reassuring me.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Brad_HBrad_H Posts: 35
    edited 2009-01-10 04:45
    Hello Whit

    Maybe not for the electronics but I think static electricity should definitely be a concern·if your power source·uses combustible fuel.

    Brad





    Post Edited (Brad_H) : 1/10/2009 9:39:33 AM GMT
  • WhitWhit Posts: 4,191
    edited 2009-01-11 13:44
    Thanks Brad,

    The robot I am working on is all electric.

    You are right, you would want to be careful at re-fueling with a compustable fuel bot.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
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