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help with parts

Discussion in 'General Electronics' started by Dwayne, Mar 18, 2005.

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  1. Dwayne

    Dwayne Guest

    Total know nothing here :)
    I have an idea but could do with some help finding the parts to work out a
    circuit.
    first off I need to clip a wire onto a HT lead on a car engine which will
    give me a pulse once every 4 turns of the engine (or I could put it on the
    main feeder lead which would then pulse every turn either way is fine )
    So this HT signal would need to be converted to a safe usable voltage: I am
    thinking small transformer with a voltage regulater or a optical device or
    even getting the signal from the low voltage area of the ignition (not ideal
    I want the unit simple to clip on or off and for any make of car).

    Next this signal would need to be fed to a PWM, I am thinking that I would
    need to change the pulses to a variable voltage which could be used to
    control a simple 555 based pwm circuit. what would be the simplest way of
    achieving this?

    Then the output from the PWM would need to be fed into a transistor capable
    of running a motor of around 20amps.

    So the block diagram would look something like:
    HT pickup - useable pulse - analogue signal - PWM - transistor - motor

    as you may have guessed I want a motor that runs faster and slower dependant
    upon the rpm of the engine.
    thanks in advance for any help.
     
  2. Andy P

    Andy P Guest

    Can I ask what for? Just a big guess here...but I would suggest
    spending the money on the turbo or supercharger. If your trying to make
    a hybrid type of setup, this is not the way to do it. If I'm way off
    base, then I appologize.

    In answer to your question...

    Inductive pickup (like on a timing light)- schmitt trigger -
    (optional)optoisolator -frequency to voltage converter-pwm
    controller-high current darlington-bigger transistor (probably a fet of
    some sort, check the specs to be sure).

    Honestly, if your a know nothing as you put it, this may not be the
    project for you. Your going to be dealing with massive voltages on one
    side, and massive curents on the other. 100miliamps and/or 30 volts is
    enough to permanently stop your heart. On top of this, a failure in the
    system could mean a total failure in any one of the dozens of systems in
    the car. It really is a safety risk not only to you, but to anyone
    around you when it happens while your driving.
     
  3. Dwayne

    Dwayne Guest

    your spot on but I fancy experimenting and will continue despite the
    previous rather disapointing results from electric superchargers. You never
    know i may just come up with something no one has thought about.
    thanks have found some some parts from your description.
    OK maybe know nothing was a tad understating myself. I do understand the
    dangers of the voltages and currents involved (just one of the reasons I
    wanted a non intrusive method of getting the signal from the car) I have a
    little experience with electronics, not a lot admitedly but some.
     
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