Motion sensor needs to supply at least 5 mA. Help...

Discussion in 'The Projects Forum' started by And123, Apr 22, 2009.

  1. And123

    Thread Starter New Member

    Mar 8, 2009
    You've all been helpful in the past, so here I go...

    I'm building a pinewood derby racetrack that is PLC controlled. The finish time and place of finish of the racecar is determined by a phototransistor sending a signal up to a TTL input card (5 volts).
    In order for a signal to register high the manual says at least 5 mA are needed, I've tried working with what I have; this involved using no resistance in the phototransistor circuit and holding a incadescent bulb pointblank to the phototransistor. The best that could be done was about 2 mA from the circuit into the input card.

    I'm open to any suggestion on how I could get this to work, anything. Just try to keep it in the realm of 5 volts (24 volts and below is an option). This project is due in two weeks, we're making headway but things need to get done.


  2. hgmjr


    Jan 28, 2005
    Can you supply the part numbers of the phototransistor and the emitter?

  3. And123

    Thread Starter New Member

    Mar 8, 2009
    Yeah, the phototransistor is a radioshack infrared sensor:

    Model: 276-145
    Catalog #: 276-145

    I'm using a incadescent pin light to activate it.

    My concern isn't these components, I don't think anything will fix this. Something else needs to be done to activate the plc input module...