Programmable timer for appliance
The team of dreamlover technology published many advanced level project including timer based project. Here is a very useful and attain grabbing project programmable timer for appliance used to control any appliance whenever we want. The main or primary work of the project programmable timer for appliance is to switch on and switch off the appliance in selected preset time. The wide range of the time period variation (from 8 second to 2 hour) and working in two modes; off timer and cyclic mode lets this project towards programmable universal timer. The appliance is turn on after preset time by setting switch SW2 similarly; appliance is off after preset time by setting switch SW3.
Circuit Description of programmable timer for appliance
With the combination of two 14-bit binary ripple counter (IC2 & IC4), three quad two input NAND gate ICs (IC1, IC3 and IC5) and a relay driver transistor with some passive component the project programmable timer for appliance is successfully completed. The NAND gates (N3 with N1 and N2) here is used as first oscillator and NAND gates (N4 and N5) is used as second oscillator and provide clock pulse to binary ripple counter IC (IC2 and IC4) respectively at rate of one pulse per second where timing control circuit formed by NAND gates (N6, N10 and N11) is used to inhibited the rate of pulse.
Lastly the transistor relay driver transistor T1 with NAND gates N8 and N9 is used to energize the relay. Here for heavy load, a higher current rating relay is used in order to control the appliance.
Resistors (all ¼-watt, ± 5% Carbon)
R1, R3 = 4.7 MΩ
R2, R4 = 1 MΩ
R5, R8, R9 = 1 KΩ
R6, R7 = 2.2 KΩ
VR1, VR2 = 1 MΩ potentiometer
C1, C4 = o.33 µF
C2, C3 = 0.01 µF
C5 = 1000 µF/35V
IC1 (N1 – N3), IC3 (N4 – N7), IC5 (N8 – N11) = CD4011 (quad two input NAND gate IC)
IC2, IC4 = CD4020 (14 – bit binary ripple counter)
D1 = 1N4007
T1 = BC548
LED1 = RED
LED2 = GREEN
RL1 = 12V, 200Ω 1C/O Relay
SW1 = ON/OFF switch
SW2, SW3 = Rotary switch (11pole rotary selection)
SW4 = Slide switch (mode selection)
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