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Why does the Basic Stamp RESET periodically?

Discussion in 'Electronic Basics' started by Julia Goolia, Feb 4, 2004.

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  1. Julia Goolia

    Julia Goolia Guest

    Hi,

    I am running a basic stamp to control a step motor. My program looks
    something like:

    MAIN:
    debug "start"
    LOOP:
    debug "LOOPING"
    <some code>
    GOTO LOOP

    The weird thing is that when I run the program, the debug window will
    first show "start", then "LOOPING LOOPING LOOPING" etc. However, now
    and again, it will print "start" again without me touching the 9V
    Duracell power supply. The BS outputs are going to a transistor array
    which provides more power for the stepper.

    Does anyone know why this happens?

    Thanks!
    juliabean
     
  2. CFoley1064

    CFoley1064 Guest

    From: (Julia Goolia)
    Hi, juliabean. Some general observations:
    * You aren't running that stepper motor off of the 5V output from the stamp,
    are you? If so, have mercy on that li'l SOT-23 regulator, wouldja? Use a
    separate power supply for the stepper, and wire the separate power supply
    common and the stamp common together.
    * Always try replacing the battery with a fresh (and known good) one first. If
    your input voltage to the stamp regulator drops below about 6.5V, even for a
    fraction of a second, a reset will be generated on board. One thing you can
    try is momentarily placing a 330 ohm resistor across the battery while you're
    program is running, and seeing if that causes a reset.
    * Look at your layout. Make sure you're not getting even momentary overload on
    any of the output pins. From memory, I think you can get about an extra 40 mA
    out of the on-board regulator (check this) -- if you exceed that even
    momentarily, the +5V drops and a reset goes out.
    * Keep power wiring away from the stamp, and the signal input and output lines.
    If you've got high current wires right next to signal wires, you're asking for
    trouble.
    * If you're driving relays, watch for contact arcing. That can upset the
    stamp. Try to drive only resistive loads with relays, or if not, then place
    the relays as far as possible from the stamp. Remember Sesame Street -- "The
    Solutrion...To Pollution...Is Dilution!" Of course, that's not good enough for
    the EPA, but the EMI from contact arcing is diluted by moving it farther away.

    There may be more suggestions, but these have worked for me in the past.

    Good luck
    Chris
     
  3. Julia Goolia

    Julia Goolia Guest

    Chris,

    Thank you so much for your suggestions! I really appreciate you
    taking the time... I'm learning so much!

    I have plugged in a 12V 200mA transformer (which plugs directly into
    the wall) into the basic stamp (actually I'm using the BASIC STAMP II
    OEM... I guess thats important!). I also use a transistor array and
    the same power supply to power the stepper. That is, I am not
    powering the stepper motor directly with the outputs from the stamp.
    However, I'm not using a separate power supply either. That is, I
    only have the 12V 200mA supply, and the + goes into the Vin pin and
    the - goes to the Vss pin (I do not use the 5V Vdd pin). The + from
    the supply also goes to the stepper wires and the COMMON input of the
    transistor array. And, the - goes to the center tap of the stepper
    and the ground of the transistor array (i think that is how it
    goes...i'm at work right now so i can't check). Basically, both the
    basic stamp and the stepper share a common ground.

    One more thing I noticed: I have a new layout and it doesn't happen
    with the step motor anymore... however, if I remove one the stepper
    coils and replace it with an AMPMETER, it happens! Is it possible
    that the AMPMETER is draining all the power so that the basic stamp
    gets nothing? I thought the transformer would just suck more power
    from the wall.
    Why is this? I guess its cause the current through the wire creating
    a magnetic field which disruptes the current flowing through the
    stamp? In my case they are quite close... about a few centimeters.
    This may be the problem.

    Thanks for your help once again... I'm going to investigate this
    weekend.

    And don't forget this from Sesame Street:

    1 2 3 4 5 6 7 8 9 10 11 twe e e e e e elve.

    juliabean
     
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