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Modifying Radioshack's zip-zap lap timer to trigger camera flash

Discussion in 'General Electronics Discussion' started by berkleeb, Mar 20, 2012.

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  1. berkleeb

    berkleeb

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    Mar 19, 2012
    Hi everyone,

    The attached link describes the functionality of the toy, but here's a summary of it anyway. Zip zap is a lap timer for toy race cars made by Radioshack. It consists of 2 pairs of IR sensors. Every time the 1st IR beam, followed by the 2nd beam, is disrupted, the counter would start counting - until the car passes the 1st and 2nd set of IR again. What's interesting is that whenever any IR beam is disrupted, a Red LED on top of the timer would light up, then off again, when the beam touches the photocell again. The camera flash is triggered by a short circuit (by means of a mono audio jack or a hotshoe).

    Based on Pete's blog, I should be able to just replace the LED on top of the zip zap counter with a 3.5mm mono audio female jack (since the LED circuitry would be o/c when the IR beam is not disrupted and s/c when IR beam is disturbed). My multimeter is reading continuity as expected, but the flash isn't flashing. He mentioned a diode in his blog, but I'm not sure what is it used for. Does anyone have any advice on what else I can try?

    http://petetek.blogspot.com/2010/02/299-laser-trigger.html
     
  2. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    My first thought would be there is not enough current being supplied by the zip zap counter through the old LED wiring. LED's have very limited current requirements.

    Are you using the exact same flash as pete? Do you know the requirements to get the flash to work?
     
  3. berkleeb

    berkleeb

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    Mar 19, 2012
    Jackorocko,
    Thank you for your reply. I'm using the pocket wizard, as described by Pete. The zipzap uses 2 AA batteries, so power is minimal. The IR LED has its own power powered by 2 AAA batteries. The pocket wizard is a wireles system that allow for remote flash trigger. It contains its own battery, so does the flash.
    Generally all flash build up charge on one side of the terminal, waiting to be short circuited to produce the flash caused by electrons being pulled to the positive terminal. Hence the flash unit or the pocket wizard requires only a simple short circuit to activate the flash.

    Here's a bummer. Regardless of whether the IR beam is broken or not, the flash keeps going off whenever I touch its second terminal to the terminal of the zipzap. But once it's connected, the flash will never go off again - until one of its terminal is disconnected and reconnected again.

    Do you know why it's doing that?
     
  4. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    probably because you are grounding the device and completing the circuit. It would make sense as to why it never recharges until you unplug the device.

    What I don't get is this. If the device only requires that there needs be a short circuit between two wires (continuity) to trigger the flash then why are you wiring it an external power source? I would think something like an optocoupler or maybe a small relay would be a better choice.
     
    Last edited: Mar 20, 2012
  5. berkleeb

    berkleeb

    4
    0
    Mar 19, 2012
    Thanks for your patience. I probably did not explain the situation clearly. I want to take photos of birds flying, and so I'm using the IR beam from the zipzap as a sensor to trigger the camera flash. When the IR beam is not broken, the terminals where the audio jack / red LED is open circuit. When the birds fly through the IR beam, it closes the circuit of the Red LED, hence lighting the LED up.
    For example, when a multimeter (in continuity mode) is connected in place of the audio jack / red LED, it beeps only when the the IR beam is broken. Now, when he multimeter is replaced with the audio jack (that's connected to the flash), it shouldnt be completing the circuit when the IR beam is not broken, unfortunately that wasn't the case.

    Is it making more sense now?
     
  6. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    can you short the two wires on the flasher 3.5 jack and get the flasher to go off?
     
  7. berkleeb

    berkleeb

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    0
    Mar 19, 2012
    Yes...
     
  8. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    Then why are you supplying power to the flasher via the LED circuit of the zip zapper? I am sure it has something to do with the voltage source that is being applied to the flasher circuit, but I don't know exactly how they operate so I am at a lost of what to advise you. If it was me I would find out how much power the zip zapper is putting out in that LED circuit and either modify it or use it to control some form of switch, ie. a transistor, relay, optocoupler etc.
     
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