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I guess I shorted out my activity bot — Parallax Forums

I guess I shorted out my activity bot

JonPeytonJonPeyton Posts: 10
in Robotics
Its running the servos and encoders while in power pos 1.
I was doing a servo tutorial and I must have not put a jumper on correctly.It worked fine this morning while connected to USB but when I put the new batteries in to calibrate it it started going nuts.
Anyone know what the next step is as far as what needs to be replaced?
Thanks,sorry if this isnt in the right spot.
Jon Peyton

Comments

  • JonPeytonJonPeyton Posts: 10
    edited 2016-01-14 04:17
    well I re ran the calibration.
    p26&27 led were staying on constantly so I didn't have much hope but it went through its paces and the lights went off so maybe it was just a snafu.
    I actually just remembered that I had tried to run the calibration this morning but the batteries were too low so maybe it was just running that when I reloaded fresh batts...weird how it was doing in power position 1 but who knows.
    Gonna push on with the nav. tutorials tonight so we'll see.
    I love this thing, when I thought I had fried it I felt like I ran over the dog or something I guess we've bonded over these two weeks of learning....lol.
    Jon Peyton
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2016-01-14 04:37
    Jon,

    I doubt that you've done anything bad to your ActivityBot. I've seen several bots behave as you describe: motors running with the switch in position 1, without prior provocation. I know that there have been issues with the switch; but in at least one instance, I've replaced the switch, and the behavior persists. There's something else going on with the electronics, and I don't know what it is.

    But whatever the case, the anomaly doesn't seem to be injurious to the bot's performance, rather just an inconvenience. The simplest work-around is to place the bot on a pedestal when programming so that it doesn't run off of your desk when the program takes over.

    -Phil
  • GordonMcCombGordonMcComb Posts: 3,366
    Is this with the Parallax servos included with the ActivityBot, or a different set? What happened is that with the switch in Pos 1, the power for the servos came from the signal line. That's can be a potentially damaging condition, but as Phil says, it's unlikely to harm the Activity Board. The reason: the board contains series resistors inline with the servo header pins, so that current is limited to a safe level if voltage is pulled through the signal line. The servo itself is unlikely to be harmed, but it probably won't run well, as there's very little current made available for the motor.

    To be on the safe side, if you get it back working, when you have servos connected to the servo header, put the switch in Pos 2 whenever running code. Phil's suggestion of putting the bot "up on blocks" is the way to go. I always like to have the visual feedback of the motors turning. Nothing like working with code for a half hour, only to have the thing just set there when you switch everything on.

  • JonPeytonJonPeyton Posts: 10
    That's a really good idea!
    I like to do that with my motorbike when I'm working on it also just to be able to test things in the drive chain or gears without it fleeing from me lol.
    I actually think some of my issue may have been that the input wires to the encoders weren't all the way inserted.If you "He-Man" them into place theres a confirmatory click.I suppose I was a bit reluctant to use a lot of muscle the night I assembled it out of fear of damaging it.
    The action in position 1 only occurs if the battery barrel is plugged in.Using USB only is safe.
    Thank you Phil and Gordon for taking the time to help.This sure is a lot of fun!
    JonPeyton
  • ercoerco Posts: 20,255
    Jon: Good to hear your bot survived to fight another day. Guard that magic smoke inside the chips and don't let it out!
  • JonPeytonJonPeyton Posts: 10
    Yup were up and running!
    Learning about ticks per second today, lol.
    One thing that seems strange is how close the inside upper wheel is to the part of the encoder where you attach the wire.Its almost certainly rubbing.I know the encoder counts the spaces in-between spokes for data but that's a bit further back. I hope the little guy isn't being impeded by this situation.I re tightened the screws just to be sure I was within spec, but all seems normal.
    The Dog is deeply troubled by it all..
    JonPeyton
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