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

Missing pulse detector
Pattern generator
Car Battery Charger12V circuit and explanation
50MW Audio Amplifier circuit
radio frequency rf watt meter circuit
digital step km counter
12 Volt DC Fluorescent Lamp Driver
Simple short range portable FM transmitter circuit diagram
pressure sensor circuit
Scalextric Lap Counter