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Strange problem help needed!

Discussion in 'General Electronics Discussion' started by SJW2511, Oct 20, 2014.

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  1. SJW2511


    Oct 20, 2014
    Ok bit of a strange one here, and bear with me because Im a little bit of a noob with electronics.

    Basically I have a couple of lasertag guns, they have 3 what I believe are IR sensors on them to detect the hits, what Im trying to do is extend the sensors away from the gun.

    the sensors themselves are black 2 pin IR receivers (I think)

    Anyway I removed the sensors off the pcb no problem, then I attached a 12inch wire to each point where it was joined with the sensor then attached on the ends of these wires.

    Tested it out and it received hits on the sensor perfectly, however the gun wouldn't fire properly, it was sometimes not firing at all, then sometimes it was taking a few seconds for it to fire after pulling the trigger. This is where it gets strange to me...

    Removed the sensor and left the wires the same length but with no sensor or anything on the ends, same problem. However if I cut one of the wires down to about an inch, or remove it altogether the gun works fine!?!? What is this voodoo? why would it matter how long the wire is especially as there is nothing even on the other ends of the wires?

    The only thing I can think is perhaps the wires are acting as some sort of aerial, or causing some sort of RF interference? in which case would using shielded wire help?

  2. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    Yes and Yes. The IR Rx circuitry will probably have a high gain amplifier of some kind which could pickup external noise. I don't know why the gun doesn't fire, maybe it does but it's just too fast for you to see and then it detects what it thinks is the return beam straight away. Or if it's receiving anything it just might not fire, that might be part of how it works.
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Do the guns have any feature that deliberately prevents them from firing in response to some condition they may have detected? Have a look at the documentation to see if there's any circumstance in which the gun is unable to fire, by design. That may give you a clue as to what it thinks it's detecting.
  4. BobK


    Jan 5, 2010
    I would guess that it is disabling firing for a time after a hit. And the added wires are introducing enough noise to make it think it is seeing hits.

    An IR sensor would normally have 3 leads. Can you show a picture of the sensor and the circuit board?

    KrisBlueNZ likes this.
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