repeating timer


Posted on Feb 6, 2014

This timer is based on a simple Monostable Circuit. The length of time the relay remains energized - the ON period - is controlled by the values of R3 & C2. And the length of time the relay remains de-energized - the OFF period - is controlled by the values of R4 & C3. With the component values shown - periods of up to 30 minutes are available. Th


repeating timer
Click here to download the full size of the above Circuit.

e length of time the relay remains energized is controlled by the values of R3 & C2. And the length of the time the relay remains de-energized is controlled by the values of R4 & C3. Owing to manufacturing tolerances - the precise length of the time periods available depends on the characteristics of the actual components you`ve used. You can choose component values that suit your own requirements. You should get about 70 seconds for every 1Meg/100uF. So 4M7 & 100uF will give about 6 minutes. And 4M7 & 1000uF will give about an hour. If your time periods don`t need to be too precise - and more-or-less is close enough - you can replace the pots with fixed resistors. Do not use the "on-board" relay to switch mains voltage. The board`s layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay somewhere safe - Away From The Board. The timer is designed for a 12-volt power supply. However - it will work at anything from 5 to 15-volts. All you need do is select a relay to suit your supply voltage. I`ve used a SPCO/SPDT relay - but you can use a multi-pole relay if you wish.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    i2c interface to USB interface
    Auto-advance projector
    Divide-multiply-with-only-one-trim
    Cheap 12V to 220V Inverter
    Detector circuit
    hall effect switch
    light activated led
    battery charger circuit
    Water level indicator circuit using CMOS ICs
    Bistable Multivibrator (Flip-Flop)
    how to convert a 9v battery to 3.7v
    96 ford explorer: My headlights do not work interior lights
    A delay circuit battery



    Top