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Thread: Removable link rule clarification

  1. #1
    Ocracoke's Avatar
    Team Kaizen

    Hi everyone,

    With regards to the rules regarding removable links, does the link have to be on the main power circuitry, going from the batteries to the motors or can the link be on the RC equipment which, when removed, causes the robot to lose all power anyway?

  2. #2
    the link has to be fitted before any electronic hardware in the bot.

  3. #3

  4. #4
    Ocracoke's Avatar
    Team Kaizen

    Thanks for the clarification - got a date with the soldering iron tonight. :P As The Honey Badger uses SLA batteries rather than LiPo batteries, I presume a inline fuse isn't required?

  5. #5

  6. #6
    If you're not using a lipo battery, then a fuse isn't mandatory. However it is highly advised as a protective measure. I never used fuses before I switched to lipo batteries, but I probably would now if I was switching back to an older battery technology.
    Jamie McHarg
    RogueTwo Robots

    With great power, comes great reliability.

  7. #7

  8. #8

  9. #9
    In a car, negative and positive are very different from a practical point of view. The battery negative is grounded to the chassis, so it's not insulated. If you jump-start a car, you just connect the negative side of the live battery to the chassis of the car with the dead battery - the whole car is earthed to the negative side. In theory you could make a car with the positive side earthed to the chassis instead, and everything would work the same as long as you reversed the polarity of the other components (otherwise the starter motor would run in reverse and so on), but components like that are all designed with a negative earth connection.

    The upshot of that is, if you want to make a car electrically safe you unplug the battery negative terminal. Now the battery is ungrounded, there's no return line for any of the positive connections and so no current can flow unless you short the actual battery terminals. If, instead, you unlpugged the positive connection, you could still short between the positive battery terminal and any metal part of the car.

    In a robot the wiring is all insulated, so in theory there should be no difference where you put the link. You have a self-contained circuit with no ground to short against, so no break point is safer than any other. I don't know why you'd see more sparking etc. with a negative break... maybe the way some electronic bits are wired up (electrolytic capacitors have polarity)? But nothing can "flow" to or from either terminal when the other terminal is isolated, the direction that electrons are moving is irrelevant.

    Still, I agree that it's better to just put it on the pos side for the sake of convention! If that's where the tech checker expected to find it, it makes everyone's life easier to put it there unless there's a good reason not to...

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