Optical triggertesting

Discussion in 'General Electronics Discussion' started by Ed Sowell, Jan 15, 2018.

  1. Ed Sowell

    Ed Sowell

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    I have an aftermarket electronic ignition system in my '76 Jaguar XJ-S. It uses an optical trigger over the edge of a slotted shutter disk in the distributor. The car recently died and I traced the problem the ignition, and a tests on the oil and the electronic control module showed them to be OK. This leaves the optical sensor, so I ordered a new one:

    https://tinyurl.com/y9nveqp7

    Wanting to be sure it worked, I decide to test the trigger before installing. I connected it to the control module and manually passed the edge of the shutter disk between the LED and the sensor of the optical trigger. The control module has a test LED that flashes when triggered, and it correctly blinked. Then, I did it a couple more times just for good measure. After that, the test LED says on all the time.

    So, here's the question: Did I fry the optical trigger, or has it merely been left in the wrong state which will get reset when installed in the distributor and sees a regular sequence of slot passings?

    TIA

    Ed
     
    Ed Sowell, Jan 15, 2018
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  2. Ed Sowell

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It is possible that you did something to the sensor. It is also possible that you did something to the control unit.

    How expensive are the sensors?

    How sure are you that you wired it up correctly?

    Do you remember what state the controllers LED was in when the sensor is disconnected? Does it do the same thing now?
     
    (*steve*), Jan 15, 2018
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  3. Ed Sowell

    Ed Sowell

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    The control module still responds to momentary shorting of 2 of the 3 wires that connect to the trigger, meaning the module is OK. trigger is about $35 plus postage. I am sure about the wiring. Can't be sure about initial state, but in normal usage the system has to be able to start from any state since there's no way to know exactly where the shutter is when the engine stops.

    I'll be leaving shortly, but will be anxious to hear your further ideas when I return later this morning.

    Ed
     
    Ed Sowell, Jan 15, 2018
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  4. Ed Sowell

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Measure the resistance across the 2 connections to the sensor that if shorted simulate the triggering. Do this with nothing else connected to the sensor. Read the resistance both ways (i.e. repeat the measurement after swapping the meter probes over). Tell me both readings.

    Does the LED on the controller come on when you plug in the sensor and go off when you unplug it?

    Was the LED normally on when the shutter disc was blocking the sensor, or when it was not?
     
    (*steve*), Jan 16, 2018
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  5. Ed Sowell

    Ed Sowell

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    Connected either way, the DVM shows no connectivity. IOW, infinite resistance.

    That is correct

    I didn't notice.

    BTW, I've ordered a replacement part. they are sending me an RMA.

    I appreciate your efforts. Thanks.

    Ed
     
    Ed Sowell, Jan 16, 2018
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