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Plenty of smoke left? — Parallax Forums

Plenty of smoke left?

Dave MatthewsDave Matthews Posts: 93
edited 2009-09-01 21:04 in Propeller 1
I am working on a project that uses the Prop USB proto board, and the deadline is this Wednesday. Last weekend I had everything running (4 servo motors, some LEDs, assorted sensors), until I must have done something wrong and the prop chip died. This was a workbench lash-up, so I decided I had shorted something with all the loose wires and such. Fortunately I had a spare proto board and I was able to move my circuitry to the new board which was tedious but ok. Today after completing the rebuild, I checked my work, etc. Applying power, all looked good. I started working on the program, running servo motors using the "Three_Servo_Assembly Author: Gavin Garner" example as a base. While trying to get a motion I wanted, I notice a puff of smoke from the back of the proto board, and I promptly removed power.

Given the impending deadline, my body was covered in sweat and my heart had sunk into my shoes (I know, I take some things far too seriously <g>).

After looking everything over, I found no wiring problems, no mark of a burnt part, nothing! Powered back on and everything runs as before. I put an ammeter in series with the supply and did not notice any current excesses as I tried the various routines I was working on. No evidence of a problem except the now barely detectable smell of a burnt component.

Although relieved that there seems to be sufficient magic smoke left in my prop chip (or a proto board component??) to allow my project to move forward, I am really concerned and curious about what happened.

Dave

Comments

  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-08-31 21:43
    A lot of surface mount components can burn and not change shape or colour. I have never seen the back of a proto bd so it is difficult to say what the problem could be. If you do some selective sniffing there may be some answers. ( If you use a staw, and get discovered, just brazzen it out)

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  • TimmooreTimmoore Posts: 1,031
    edited 2009-08-31 21:44
    Check the inductor near the servo connections, top right of board if power plug is top left. I have overloaded it and had it smoke/flame but continue working after but iwth increased resistance.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-08-31 21:59
    Yeah. That inductor has a limited current handling capacity, certainly not enough to keep 4 servos fed.
  • TimmooreTimmoore Posts: 1,031
    edited 2009-08-31 22:04
    I had a software bug and had the wrong halves of a h-bridge on, it ended up drawing lots of power
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-08-31 22:07
    It may just have been a tiny solder bridge that vaporized, since it came from the bottom.

    -Phil
  • Dave MatthewsDave Matthews Posts: 93
    edited 2009-09-01 21:04
    Thanks everyone for the input. 24 hours later, and everything is still working. Tomorrow this control gets installed.

    As an aside, I am not using the prob board servo inductor for the servo power distribution, I have a separate circuit for that.

    This is my first major Propeller application, and it was a BLAST. This chip had restored the excitement of programming for me that I first felt decades ago with the Motorola 6800 but seemed to lose over the years.

    Great chip!

    Dave
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