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Thread: Electronics guys, I need your help!

  1. #1
    n00b 4 life mp3oplecarrier's Avatar
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    Electronics guys, I need your help!

    I am trying to make a very stealth install where my screen, keypad and Streetpilot GPS are hidden away when the ignition is off. I have already made my PC case which houses a keypad and mouse that are hidden by an electrically operated sliding cover (see this post Estima CarPC v2.0 build up pics). I am now trying to sort the controller for that, what i have used in the past is 2 douple pole relays wired to stay on until the cover meets a normally closed microswitch. This means that the acc circuit going live can make the motor run one way, and going off, move it the other. (sorry if not explained well, it's bedtime!).

    What I am trying to do and where I need help, is to use SCR's instead of relays, and I found this circuit in a VERY old book that seems to do what I want, ie S1 switches on the load until S2 is broken. However it says that it will not work with DC motors which I presume means it needs a resistive load rather than inductive.

    Would this work if I put a resistor in parallel with the motor? If so could you suggest a value? The motor runs on 1.5 volts and draws about 300ma

    Thanks
    Steve
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    ....Yes, I know it has a stupid name, those crazy Japanese!

  2. #2
    Newbie
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    Why not just use a transitor (fet) or even better a mosfet? Just get a P channel if you want it to turn on with hot gate. N channel if turned on by grounding the gate. (weak pull down/up resistors to help any floating votages)

  3. #3
    n00b 4 life mp3oplecarrier's Avatar
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    Thanks for the reply Anode, that's just my problem as I am happy designing what I want my projects can do, and can build the circuits but my electronics knowledge is pretty poor and I need my hand held?

    Any chance of a circuit (stripboard buildable?)

    Steve
    ....Yes, I know it has a stupid name, those crazy Japanese!

  4. #4
    Constant Bitrate
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    The motor runs on 1.5 volts and draws about 300ma

    so what voltage are you going to use to run this motor 12V?
    30 ohm 5w resistor in series with the motor?
    cant see that little bit of inductance dominating a 30 ohm resistive load

  5. #5
    Variable Bitrate choyak's Avatar
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    I think that the SCR has a voltage drop of about 1.5 volts when it is on. You could use a mickey rig with 12 volts and an SCR with a 5 watt 9 volt zener in series with the motor that would probably work, but it is a super ghetto way to do it
    Carputer currently 'ghettoed' into car!!!

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