Magic Transistor?

Discussion in 'General Electronics Chat' started by TehDawg, Feb 4, 2011.

  1. TehDawg

    Thread Starter New Member

    Feb 4, 2011
    Good day forum!

    This morning I had someone bring in a "water depth meter". I works by dropping a wire down the "bore-hole" and when the metal end touches water it makes a beep on the surface (The water closes the circuit).
    Now the device broke, and when we opened it, there was a 9V battery, a PNP transistor and a buzzer. One of the transistor legs were broken off. But strange enough we fixed it without the use of a transistor.
    My question now is, what was the transistor for?? We were stumped to figure out what it was for, and still don't have a answer. Any input is much appreciated!


    Teh Dawg
  2. Adjuster

    Late Member

    Dec 26, 2010
    The transistor may have supplied gain, to ensure that the circuit would work even if the water was very pure (and thus of low conductivity) - perhaps you are testing it with less pure water?
  3. debjit625

    Well-Known Member

    Apr 17, 2010
    It was broken or it was never their,because many circuit use a transistors as a diode or in many case a kind of resistor also_Once I used the base emitter junction as a temperature sensor,that time I only needed the base and emitter pin and broke the collector pin and using that as a diode.

    Good luck
  4. SgtWookie


    Jul 17, 2007
    Well, you wrote "PNP transistor", but not the part number of it.
    It may have been a high-gain Darlington, like perhaps an MPSA14, that amplifies the current on the base by ~20,000. This is important if the water is very clean.