Now, a day automation task is necessity not only in industrial sphere but even in the domestic sphere.
The project universal timer in this website is unique because it offer an ultra wide range of time period having pin point precision anywhere (i.e. not affected by ant physical factor) from one – tenth of a second to hundreds of hours. Due to feature “auto latch” facilities and low power consumption CMOS IC used plus such a low current consumption on that most multimeter would fail to detect it. The above facility with low costlier and familiar design make the circuit “The Universal Timer ” more versatile.
Circuit description of universal timer
High frequency signal of several kilohertz is generated by IC1 CD4060, and VR1 is used to remove device imprecision errors. The internal frequency divider of IC1 divides the base frequency by a factor of 213 times i.e. 16384 times.
The output frequency of 10 KHz from pin 3 of IC1 is simultaneously divided by set of five CD4017 counters (IC2 – IC6) by 10, 6, 10, 6, and 10. Here IC2 to IC6 is configuring in maximum mode and divided-by-six decimal mode respectively where output is selected by range selector switch SW1.
The output time period from range selector of universal timer switch is 0.1 second, 1 second, 0.1 minute, 1 minute, 0.1 hour, 1 hour respectively given to two serial connected counter CD4017 (IC7, IC8). The outputs from range selector provide precise master clock frequency, counted by IC7 and IC8. IC7 and IC8 counts one and ten master pulses respectively.
The timer section of universal timer is control by two rotator switch SW2 and SW3 as shown in circuit diagram figure 1.
NAND gate N1 is used to change the state of output from SW2 and SW3. The feedback diode D1 helps to latches the next NAND gate N2.
Lastly a relay driver transistor T1 is used to drive relay connected to collector of transistor T1. The relay contacts can be selected to switch the load ‘ON’ or ‘OFF’ after the preset time. Switch SW4 (Push-To-On switch) is used to reset the whole circuit. Power supply interruption also reset the entire circuit of universal timer.
NOTE: Connect a device to a timer and set it to short period, say a few seconds, and adjust VR1 till exactly that time delay is obtained. The accuracy on rest of the range will follow automatically.
PARTS LIST
Resistors (all ¼-watt, ± 5% Carbon)
R1 – R4, R10, R11 = 1 KΩ
R5, R6 = 10 KΩ
R7 = 47 KΩ
R8 = 24 KΩ
R9 = 100 Ω
VR1 = 4.7 KΩ
Capacitors
C1 = 0.0001 µF ceramic
C2 = 100 µF/25V electrolytic
Semiconductors
IC1 = CD4060
IC2 – IC8 = CD4017
IC7 (N1 – N2) = CD4011
T1 = BC547 NPN transistor
D1 – D3 = 1N4148
Miscellaneous
SW1 = Single–pole 6–way rotary switch
SW2, SW3 = Single–pole 10–way rotary switch
SW4 = Push-To-On switch
SW5 = On/Off switch
SW6 = SPDT (Single pole double throw)
RL1 = 300 Ω 12V relay
LED1 = RED
LED2 = Green
