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Problem with robot — Parallax Forums

Problem with robot

ObiwanObiwan Posts: 36
edited 2005-06-13 18:37 in Robotics
I just soldered the circuit for my robot and I think there might be a short.· The circuit contains two H bridges and three servos.· It is all point to point soldering so it looks very confusing with many possibilities for shorts.· I know point to point isnt the best method for a small, simple circuit board, but it was what I wanted to do.· So anyway, I set all the H-bridge pins so no current is flowing through them, to try and test the servos.· I connect one servo and give it a command.· Instead of moving how I want it to, it just emits a high pitched noise and doesn't move.· I connected an ammeter and it registered something like 130 mA.· I think that there might be a short somewhere.· I know I am not describing the situation too well and its likely that this isnt enough info for anyone to help but if anyone has an idea of a test I can do or a guess at the problem, I would appreciate it.· I'll try and post a reply to this with info from some of my testing to give anyone helping me a better idea of the problem.

Post Edited By Moderator (Dave Andreae (Parallax)) : 6/12/2005 3:10:01 AM GMT

Comments

  • dandreaedandreae Posts: 1,375
    edited 2005-06-12 14:51
    Do you have a logic probe?· You can purchase one from Radio Shack and they are not that expensive (around $12.00).· This is a handy device for checking the high and lows of your circuit.

    Dave

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  • Kevin B SlaterKevin B Slater Posts: 49
    edited 2005-06-13 18:37
    Hello Obiwan,

    · This may be just a choice of nomenclature but you use the word ‘servo’ to describe what you are driving with the H-bridges.· You do not need an H-bridge to drive a servo; it can be driven directly from a stamp.· If you are feeding an actual servo with the output of an H-bridge then you could cause damage to the servo.· A servo has three wires that are addressed as follows.· Red wire positive lead for power, usually between 4 vdc and 7.5 vdc.· Black wire, which is the negative lead for power.· A yellow or white wire for the signal which is a pulse between 1ms and 2ms.· If you are driving just a straight DC motor then you could in fact have a short in your circuit.

    · If you could post your schematic and your code you are using, we could assist you better.

    · Also download·"What's a Microcontroller" and read Chapter #4 Controlling Motion.· This chapter has is a great tutorial on controlling servos.·

    Kevin

    Post Edited (Kevin B Slater) : 6/13/2005 6:46:14 PM GMT
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