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I am working on a project building a mobile robot. I realized that the robot will have a buildup static when it is running because I can feel it when I touch it (uncomfortable spark). The robot is running on the carpet which is a kind of isolation material, so I do not think an Antistatic wheel or Grounding Strap/Chain might work on this (correct me if I am wrong)

Some critical information (Please ask me if I need to give more info)

  1. The robot electronics running on different voltage with isolated DC-DC converter running on battery. All system running on DC Voltage
  2. The low power electronics are isolated from high power and noisy electronics (motors and battery)
  3. All signals running communicating between high and low power is going through signal isolator, so it is properly isolated
  4. Some of the signal cables are shielded cables for EMI protection from high current cable, but I do not know how to ground them properly
  5. Currently no ground is connected together even the devices' chassis gnd on the high power or low power system

Simple Diagram of the Robot

My questions are:

  1. How to prevent the static buildup to shock people operating it? Is there any way to ground it?
  2. I am not sure how to ground my shielded cable, because if I ground everything (low and high power) to the robot chassis, I am afraid I will make the low power electronics noisy which will impact the signal noise
  3. What else in the electronics system that I need to ground? There are 3 grounds in my system right now, the low power ground, the high power ground, and chassis ground.
  4. How to protect my electronics (PCBs, Converter, etc) from Buildup Static which is probably located on the chassis itself? Currently I can only think to mount all electronics on plastic board with plastic standoff

If you need more information, please let me know, forgive me if the question is not clear enough as I am still not sure about ESD and how to test it

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  • \$\begingroup\$ How to ground electronics on the robot and how to reduce ESD are two entirely different questions. The question about how to ground the shielded cable can't be answered without knowing more details. Generally, ground it at one end against the chassis, but I guess you already knew as much. \$\endgroup\$
    – Lundin
    Commented Mar 24, 2022 at 7:30
  • \$\begingroup\$ if anything, you want your 'gnds' all connected together so an ESD event has a defined path rather than finding one through your isolation (which is probably only good for 2kV - which is next to nothing when talking about ESD). Also remember current flows in a loop - joining gnds won't necessarily couple noise unless there is a current path. for the noise. Read up on the Wimhurst machine and see if there is any parallel with the construction of your robot. I'd be trying an antistatic wheel as it is most likely creating the static. \$\endgroup\$
    – Kartman
    Commented Mar 24, 2022 at 9:49
  • \$\begingroup\$ I know about the "ground it at one end against the chassis" as you suspected, however in this scenario moving robot has no real ground (esp. the ground here is carpeted floor), I can assume the chassis is the ground here and connect the shield there. I thought I cannot connect all "gnds" together because I isolate the low power and high power ground since the high power ground which comes from the motor is noisy and will affect the low power line. I'd try to use antistatic wheel, but the robot will operate at a carpeted environment which I think is also an isolator to the real ground \$\endgroup\$
    – calvinglob
    Commented Mar 29, 2022 at 3:50

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You would probably want to make the electronics of the robot be like a faraday cage with the electronics inside (like a standard car, which can develop charge on the outside of it but the inside is generally zero). This will keep the electronics potential close to zero. Any buttons or antennas should be made to either not be touched by users or to have ESD protection to chassis ground. A grounding chain might help. Keep in mind it might also be the users developing the charge and not the robot but you'll have to experiment with this.

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  • \$\begingroup\$ I think it is impossible to make it like a faraday cage because some of the components like the DC motor will be located in the area outside most electronics that will be producing static and mounted on the chassis. Since the chassis is the main structure, it will go to where the other electronics are too. I will keep in mind about the charge, thanks! \$\endgroup\$
    – calvinglob
    Commented Mar 29, 2022 at 3:39
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    \$\begingroup\$ 'Like a faraday cage', a car isn't a faraday cage either, but make the chassis like a car chassis \$\endgroup\$
    – Voltage Spike ♦
    Commented Mar 29, 2022 at 4:50

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