Spark Detector

Discussion in 'The Projects Forum' started by 25pdr, Aug 10, 2008.

  1. 25pdr

    Thread Starter New Member

    Aug 10, 2008
    3
    0
    Hi Guys,

    wonder if you can help me? I have very basic electronic skills but need a circuit that will operate a relay every time a 12v car ignition coils sparks, the spark rate of the coil is once every 2 seconds.

    Thanks in advance...

    Lee
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Hi Lee,
    Is it that you need to detect whether a spark is being generated, or would it be sufficient to detect whether the ignition points are opening and closing? (assuming that the coil is being triggered from points/condenser, that is.)

    Also, relays are quite slow to react to current being applied or removed from their coils. It might take 40-80mS for the relays' contacts to close once the coil is energized. Additionally, relay contacts "bounce" when making or breaking; it takes a while for them to stop bouncing.

    It would help a lot to know more about what you are actually trying to accomplish.
     
  3. 25pdr

    Thread Starter New Member

    Aug 10, 2008
    3
    0
    Hi

    thanks for the fast response. What I need it for is for one of our Armoured Cars, we use an oxygen/propane system to Sim-fire the cannon, this is achieved by solenoid gas valves & an electronic board which triggers the 12v ignition coil. We have just added a pneumatic recoil system for the gun but need a way of starting the recoil as close as possible to the moment plug sparks. At the moment I am activating the pneumatic valves with latching relay board & a momentary switch but this is just for testing the system, I need a way of switching the board when the Gun fires(Sparks).
    The spark rate of the coil is very slow as the gun is only fired once every 2-3 seconds.

    This is the latching board I am using
    http://cgi.ebay.co.uk/Latching-rela...ryZ42899QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    Cheers Lee
     
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  4. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
    57
    Hi.
    Wrap a piece of aluminium foil to a couple of inches on the wire carrying the high voltage to the spark gap.
    Connect a neon bulb to that foil and ground.
    Glue a phototransistor to the neon bulb. Encapsulate everything so no daylight perturbs it.

    You have made a neon optocoupler, and should trigger your circuit properly.

    Yes, the opening of the points can also be used to trigger your circuit.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK - does the electronic trigger for the ignition coil apply a momentary ground (earth) to one side of the coil, and the other side of the coil is hooked to 12v?
     
  6. 25pdr

    Thread Starter New Member

    Aug 10, 2008
    3
    0
    I've attached a schematic of the system, the solenoids have a fill time of 1second & then switch off, the coil is triggered 20ms after this..

    Cheers Lee
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, you have a +12v trigger signal going to the coil. You could tap off of that.
     
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