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switch amperage for cordless drill

Discussion in 'General Electronics Discussion' started by mikgol, Jun 17, 2015.

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  1. mikgol


    Jul 6, 2013
    Hi there,

    I'm making a gate opener powered with a cordless drill (18v) hooked up to a 12v car battery. I know that 12v is not enough for full power, but for my purposes it has enough.

    I need to use a momentary switch to cut off power when the gate is fully open/closed. I'm thinking of using one like this:

    ... it's rated at 5A. Do you think this will work? Or will the switch fry, and possibly explode?
  2. davenn

    davenn Moderator

    Sep 5, 2009
    it mite be OK ... but you could measure the current drain of the drill motor when it is under load
    that will confirm what current rated switch you need
  3. Minder


    Apr 24, 2015
  4. mikgol


    Jul 6, 2013
    Thanks for the replies guys. Good point @ measuring current, i'll do this.
    I've already got a reversing circuit - I'm using a DPDT switch to move motor back/forward/off. I just want to add 2 pushbuttons that will close (disconnect the circuit) for each direction.
  5. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    When the motor stalls, the current will be much higher than 5 amps. It is normally 30 amps
  6. ADRT


    Nov 25, 2014
    As far as the switch exploding if it fails that's very unlikely. If current is too much for the switch the contacts will fuse causing the circuit to not open and possibly causing mechanical damage as well as an overcurrent in the circuit i.e. motor, wiring, battery. The contacts may also just melt. This will make the circuit not work at all. I would try at least a 15 amp switch with an inline fuse to the circuit for overcurrent protection.
  7. Minder


    Apr 24, 2015
    If using those light L.S.'s I would wire a .15μf cap across them for arc suppression.
    The object of the reverse connected diodes is that only two wires are required out to the switches and the motor, all in series, rather than bring a pair back for each.
    Arouse1973 likes this.
  8. mikgol


    Jul 6, 2013
    Thanks for the info guys. I don't expect the motor to stall (this switch will cut off power before the gate is fully open or closed) but I've found a 20amp microswitch so have ordered that - hopefully it will cover me.
    lol @ exploding switches - I was just kidding about the switch exploding :)
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