Description
About the Circuit:
The circuit is designed using popular timer IC named as IC1. The circuit facilitate time adjustment of both charged and discharged states of the relay. IC1 is used is astable mode. When power is on, capacitor C3 starts charging via R1/VR2/R2 and on time of pump starts. When its voltage reaches to 2/3Vcc, it starts discharging via R2/VR1/R1. Now off time of pump starts and when its voltage reaches to a value less than 1/3Vcc, it starts charging again and procedure repeats again. At the output of IC1 at pin3, on and off pulses are obtained. During on time transistor T1 turns on and relay connected at the collector terminal gets energized and in turns pump becomes on. During off pulse, T1 turns off and relay becomes off which in turn makes pump off.
Separate delays for charged and discharged states of the relay are achieved by using two diodes (D1 and D2) and two preset VR1 and VR2 between pins 2 and 7 of the IC1. The preset VR1 and VR2 provide control over the ‘on’ and ‘off’ stages of the relay, respectively.
The circuit turns on and off with setting of ‘on’ time delay and ‘off’ time delay.
Diodes D4 and D5 are used for rectification and capacitor C1 is used for filtration.
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