Then there is capacitor C1
filter voltage for stable up, and The rectified voltage will be divided into two-way. First way into the relay RY1 and second is applied into IC1(LM7805) to reduce voltage down to +5 volts and constant voltage fixed at 5 volts for apply all parts in this circuit.
The heart of this circuit is the IC2(PIC16C56) acts to set to working with the oscillator circuit on RC form at port B of IC2 (pin 6- pin 13) will acts Two characteristics are: (1.) the output for control the display of the seven segment LED by has R11-R18 for limit current to the 7′ Segment. (2) The other as input form by will get a value from switch SW1 – SW3 To perform various functions defined.
The port A (pin 17 – pin 18) will control common of the 7′ Segment by through Q1(C9012) and Q2(C9012). IC3(93C46B) will a data storage that program while in normal time. The data will not be lost. The IC3 is a Eeprom IC, the data is not lost, though there was no power supply circuit.
When we press the switch SW1, will make Q4(C9012) start, the voltage of 5 volts will flow through to pin E and pin C of Q4, through D7 and R22 go to pin B of Q3, result Q3(C1815) operating. At pin 11 of IC2, the original have conditions is “High” so is changed as “ low” immediately.
Circuit Timer Controller PIC16C56
IC2 starts counting down indefinitely. and LED 7 segment display time backwards again. While pin 2 of IC2 will send voltage to bias the Q5(C1815) works. As a result, the relay RY1 with
LED1 lights up. When the end, or press switch SW2 LED 7 Segment displays a number 00 on the relay stop at the end of the set time. If press switch SW1 again will start counting new cycle one at point IN and OPTO1 will as option In case you want be used with external devices.