water activated alarm


Posted on Feb 5, 2014

Under dry conditions, the transistor will have no bias current and be fully off. However as the probes get wet the transistor will conduct and sounding the alarm. An On/Off switch is provided and remember to use a non-reactive metal for th


water activated alarm
Click here to download the full size of the above Circuit.

e probe contacts. Gold or silver plated contacts from an old relay may be used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard. These will eventually oxidize over but as very little current is flowing in the base circuit, the higher impedance caused by oxidization is not important. No base resistor is necessary as the transistor is in emitter follower, current limit being the impedance at the emitter (the oscillator circuit).




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Wheel Of Fortune
    accelerometer amplifier circuit
    Binary Amplitude Shift Keying (BASK) or On Off Keying (OOK) Practical Circuit using CD 4016
    The Gentle Touch
    ULN2429 liquid detector circuit diagram electronic project
    Line Following Robot circuit
    20 kHz ASTABLE
    Colpitts oscillator



    Top