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.
The timer is based on IC2 CD4060 which divides by 16384 counters. The timer can be set by 1M potentiometer. After the set-time T1 switches T2 and T3 off, thus disabling the motor. The 4060 can be reset by the push-to-on switch provided.
Capacitor C4 is a starting capacitor already fixed to the motor. Relay RL1 and RL2 are 6V, 100 Ω, 6A rated relays.
The circuit can be assembled on the general-purpose PCB. Mains wiring should be made with high current stranded copper wire. The circuit being fairly simple does not pose any problem.
Note: SW1 = Normal/Strong Selector
SW2 = Continuous Selector
SW4 = Reset
Resistors (all ¼-watt, ± 5% Carbon)
R1, R6 = 1 KΩ
R2, R4 = 100 KΩ
R3 = 1 MΩ
R5 = 4.7 KΩ
R7 = 10 KΩ
R8, R12, R13 = 470 Ω
R9-R11 = 750 Ω
VR1 = 1 MΩ Lin.
C1 = 47 µF/25V
C2, C5, C6 = 0.01 µF
C3 = 1 µF/25V
C4 = starting capacitor already connected with motor
C6 = 1000 µF/25V
C8 = 0.1 µF
IC1 = NE555
IC2 = CD 4060
IC3 = CD4017
T1 – T3 = BC148B
D1 – D11, D13, D15 = 1N4148
D12, D14, D16 – D19 = 1N4001
X1 = 220V C primary to 9V-0-9V 500mA secondary transformer
M = 230V AC, ¼ HP reversible induction motor
RL1, RL2 = 6V, 100Ω Relay
SW1 = DPDT switch
SW2 = SPST witch
SW3 = ON/OFF switch
SW4 = Push-To-On switch