Periodic Timer

Posted on Jul 20, 2012

A switched timer with equal make and equal space periods timing adjustable from over 6 minutes to 38 minutes. This timer circuit is similar to the 5 to 30 minute timer except that when switch S1 is closed, the on/off action of the circuit will continue indefinately until S1 is opened again. A 7555 time and low leakage type capacitor for C1 must be used. The 6 way rotary switch S3 adds extra resistance in series to the timing chain with each rotation, minimum resistance point `a` maximum point `f`.

Periodic Timer
Click here to download the full size of the above Circuit.

The 7555 is wired as an equal mark/space ratio oscillator, the timing resistor chain R1 to R6, being connected back to the output of the timer at pin 3.The output pulse duration is defined as:- T = 1.4 R1 C1 This gives on and off times of about 37

Leave Comment

characters left:

New Circuits



Popular Circuits

Voltage window switch
Video DVM circuit
Experimental I/O board for microcontrollers
ac Validate Triac circuit
Siren sound generator circuit with UM3561
Build Your Own Gauss Meter
S1L9251X Cd-rom 48x Rf Amp Semiconductor
hiwatt custom 20 tube amp hum
Digital Step-Km Counter
Single-tube constant current charger circuit
Karaoke with integrated echo circuit