2B-SUPER TIMER TOUCH SWITCH
This project operates simply by touching. This is a electronic kind of a switch in which automatically goes of after some time when it is put ON. You can put ON your television, taperecorder, stereo, fridge, cooler,washing machine, fan, mixie, fan etc. for a limited time. This project is very small, simple and cheap.
In this circuit the popular timer IC NC555 is used. Pin no. 4 & 8 of the IC is given positive supply and pin no. 1 is given negative supply. A touch plate is connected at pin no. 2. By touching this plate a capacitor C1 [100mfd/16v] connected at pin no. 6 & 7 of IC NE555 is grounded. This capacitor is charged and discharge in the circuit. The delay time is controlled by the preset VR1 [1ME]. The own period of the project can be controlled by this preset. When the metal touch plate connected at pin no. 2 is touched then the pin no. 2 of the IC is triggered. The square shaped output is available at pin no. 3 of IC NE555. The base of transistor Q1 [BC547B] gets the signal from pin no. 3 through resistance R2 [12K]. The transistor conducts and relay connected at the collector gets ON.
Thus the relay gives supply to the equipment connected with the AC plug and relay gets OFF after the delayed time. Use the control preset VR1 [1ME], to increase or decrease the ON time of equipment. The ON time of relay can be increased or decreased by changing the value of capacitor C1 [100mfd/16v]. The circuit works properly on 9V supply.
PRECAUTION WHILE ASSEMBLING THE PROJECT
- Use IC base for the IC.
- Take care that there is no shooting on PCB while soldering.
- Check the all components of the circuit before starting the job.
- Check the negative and positive terminal of diode before connecting in the circuit.
- The size of touch plate should be kept about one Rs. coin.