This project indicates the working of TIMER IC 555. We can use this gadget in kitchen, washing machines or in different quiz games in schools. The OFF/ON time of this project can be adjusted by the Time control preset of the circuit and the washing machines , mixer grinder etc. can be operated smoothly.
TECHNICAL DESCRIPTION AND WORKING
This project has been developed and tested O.K. in our TV Engineers Technical Lab. The components and PCB used in the projects published in our books are available for sale at resonable price.
In this project an alram is employed along with the timer IC 555 . The alram comprises of two transistors. As soon as the “Push to ON” switch is pressed, the information at trigger pin no 2 becomes low triggering the IC. When the IC is triggered , the information at the output pin becomes high and the capacitor connected to its threshold pin no. 6 starts charging. The moment the output pin assumes high state, the alarm circuit connected to this pin becomes ON. Again ,when the voltage at thureshold pin reachs 1/3 rd of the supply, the output pin no 3 returns back to low state and the alram cuts off. The ON/OFF time of the alarm can be adjusted through the preset employed in the circuit.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
*Check Dry SOLDERING and short circuit in the board after SOLDERING.
*Check polarity of electrolytic capacitor while mounting on PCB otherwise reverse connection may damage it.
*First of all check all the components as per circuit.
*While mounting transistor, you should connect collector , base & emitter properly.
*Use IC base for mounting of the ICs otherwise IC may damage due to current leakage of SOLDERING iron.
IC 555 = 1
BC158 = 1
BC148 = 1
100MFD/25V = 2
.01MFD = 1
10K = 2
100K = 1
100K = 1