2B-TIMER WITH RESET
The ON/OFF time of this gadget can be set as per your requirment . The other feature of this project is that it can be reset as desired. This feature is not common with other timer projects. As such you can use this project for your TV set, Radio. In the night you can set the OFF time of your TV with the help of this project. After some time the TV will be automatically OFF.
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.
This project is based on TIMER IC 555. The OFF/ON time of the timer is adjusted through the preset. A discharge capacitor is connected to pin no 6 of the IC, which charges through the timing preset and resistance as soon as the information becomes high at its output pin no 3. When the charging of the capacitor assumes 2/3 of the supply, the information at the output pin no 3 returns to low state. As such whenever we push ON switch of the timer the output becomes high due to the negative information at pin no 2 and the transistor conducts. When the tansistor conducts, the relay becomes ON . If you want to reduce or lessen the OFF time, push the switch connected to pin no 4. This switch when pushed resets the IC as the information at pin no 4 becomes low. The relay then becomes OFF and switches OFF your radio/ TV.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
*Please use resistance of the exact value as given in the circuit.
*First of all check all the components as per circuit.
*Use IC base for mounting of IC 555.
*Check Dry SOLDERING & short circuit in the board after SOLDERING.
*Check polarity of electrolytic capacitor while mounting on PCB otherwise reverse connection may damage it.
IC555 = 1
RELAY 9V = 1
BC148 = 1
220MFD/25V [ACCORDING TO TIMING]
PUSH TO ON SWITH
10K = 1
220E = 1
100K = 1
4.7K = 1
5M = 1