relay powered ignition coil driver

Discussion in 'General Electronics Chat' started by lokeycmos, Jul 5, 2010.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    just for fun im making a ignition coil driver using an oscillating relay. i have several 12 and 24 volt relays salvaged from various appliances and they only have 1 pair of NO contacts. can someone tell me if there is a way to use these for this pupose? all the circuits ive came across use NC contacts that open when the coil is energized and thus the oscilation starts. TY
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    No. Wont work. These relays are most likely rated to 120v or 240v LOAD and 12v or 24v coils. You ignition coil is probably around 10,000v. It will jump the relay contacts no problem.
     
  3. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    the contacts would be on the primary side.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    What freq. rate do you need out of this osc?
     
  5. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    this is all im trying todo(see pic). just wondering if it can be modified for NO contacts ty
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    Normally opened means, there is nothing getting through until power is applied to the relay coil.


    So at an de-energized state, nothing is happening. As soon as you put 12v on the relay coil, the load contacts close, completing the circuit.

    So you need only to invert the signal going to the relay.

    I would be easier to order a few dollar NC relay.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    You could use a 555 timer with a couple of caps, a few resistors, a pot, transistor and a couple diodes to switch the relay coil on and off. However, just buying an automotive SPDT relay would be cheaper and easier.

    To get a really strong spark, you'll need two 0.22uF caps, one on the coil's primary + and another on the primary - terminal, both connected to ground. Switch the coil's negative terminal with the relay contacts. Use automotive ignition caps, frequently referred to as "condensers". If they ask you what you have, pick any American muscle car from the 60's and tell them that.
     
  8. Jaguarjoe

    Active Member

    Apr 7, 2010
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    I don't know the specs of the coil on your relay but for about $1.50 you can make a 555 oscillator to drive the relay (if its compatible). Then have the contacts drive the ignition coil.
     
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