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2 wire power door lock actuator with Stamp control — Parallax Forums

2 wire power door lock actuator with Stamp control

CogburnCogburn Posts: 62
edited 2007-06-12 21:17 in General Discussion
I am making a BS2 IC controlled rocket launcher.· It will launch pressurized 2 liter plastic bottles by using an actuator to remove the hold-down's that clamp the rocket in place.· I have the prototype working with a small solenoid that would push out when I brought a stamp pin high, but I want to make it so that the parts are easily obtained and inexpensive for anyone wanting to replicate the project.· I purchased a 2-wire power door actuator on the web for $4.50.· It will push out when 12 volts are connected to it and pull in when the polarity is reversed.· If no power is supplied to it, it goes "limp" I·was using a single IRF520 MOSFET to actuate the small solenoid and it returned to the original position after power was removed (by bringing a stamp pin low).· I suppose what I am asking is what is the method by which one reverses polarity on the actuator with the BS2?· Will it require another MOSFET?· Can it be done without some sort of circuit isolation so that when the reverse polarity is selected, there will be no feedback through the MOSFET?·

If I can't get this worked out, I am thinking about using a stepper motor and a cam to remove the hold-downs but I think this would be more expensive.

Comments

  • phil kennyphil kenny Posts: 233
    edited 2007-06-12 20:03
    One solution that comes to mind is to use an H-bridge. This is often
    used when it is necessary to reverse the voltage applied to a load.

    For one example see:

    http://www.mcmanis.com/chuck/Robotics/tutorial/h-bridge/bjt-circuit.html

    Estimated cost is about $5.

    MOSFETs could be used instead of the bipolar transistors.

    phil
  • D FaustD Faust Posts: 608
    edited 2007-06-12 21:17
    You could also use a relay with two switches(DPDT?) and have the wires to the actuator on the constant pins.

    1st side NC- negative

    1st side NO- positive

    2nd side NC- positive

    2nd side·NO- negative

    Then the actuator will alway be connected to + and -.· Instead of a MOSFET to control whether current flows or not, you could use a solid state relay.

    to·neg-|_____|-to pos

    to acu-|····|-to acu

    to pos-|···· |-to neg

    coil in -|___|-coil out

    Hope my makeshift diagram helps.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    D Faust
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