Nowadays, commercially available washing machines are provided with feature like auto-off timer, reversible impeller etc. Most of them have mechanical timer, reverses etc. Some are equipped with electronic timers. But they are very expensive and out of reach of the average consumer.
Electronic Washing Machine Control circuit provides all the facilities provided by reputed companies and even more. The circuit has a timer circuit which can be set to any duration from 0 to 15 minutes and can be extended to any length of time by merely changing a capacitor. The circuit has switching circuits which run the impeller in one direction for 25 seconds and stop the motor for five seconds. This cycle repeats until the time set in the timer has elapsed. An optional switch is provided to select normal/strong washes. During ‘normal’ washing, the impeller rotates in both directions alternatively with five second gap between reversals. This type of wash is suitable for delicate clothes. During ‘strong’ washing, the impeller rotates in one direction only with five second push after every 25 seconds.
Another switch is provided to select the ‘continuous’ facilities. In this mode, the impeller rotates in one direction only continuously. This mode is suitable for blankets, rugs etc.
The heart of the circuit is IC3 which is a CMOS decade counter cum decoder. The IC provides ten outputs which go high one at a time for every clock pulse applied at pin 14. The clock pulses are obtained by IC1 NE555 wired in as table multivibrator mode. The second, third, fourth and fifth outputs are OR’ed by four 1N4148 diodes (D1 – D4). Similarly, the 7th, 8th, 9th and 10th outputs are OR,ed by another four 1N4148 diodes (D5 – D8). The first and sixth outputs are left unused.
When IC3 starts counting, the first pulse is not received by any diode, and during that period transistors T3 and T2 are off and the relays are also off, disabling the motor. During counts form second to fifth pulse T3 is on and T2 is off. The motor runs in one direction for four clock pulses. During sixth pulse, once again T3 and T2 are off and the motor stops. During seventh to tenth pulses, T3 and T2 are on and the motor runs in opposite direction due to switching of winding by relay RL1 contacts.