2B-OFF TIMER WITH ALARM
THE SPECIALITIES OF PROJECT
This project is made up of transistors and automatically goes OFF after fix time. With this timer TV, electric press, fridge etc can be put OFF after sometime automatically. This circuit protects the instrument and does not allow any fault to happen. The main thing is that it allows LED to glow and buzzer to ring after the instrument is put OFF.
TECHNICAL DESCRIPTION AND WORKING OF THE PROJECT
This project has been developed and tested by our readers and sent to the “T.V.Engineers Technical lab” for publication in the book. The spare parts and PCB of the projects published in the series of our book publication or available in the market. The information of project code is given in the first and last page of the books.
In this circuit 3 transistor BC547 and 1 transistor SL100 are used. When switch S1 is pressed the relay operates through the transistors T1 BC547 and T2 SL100. The LED1 gets ON. The load connected to the relay also gets ON. Now transistor T3 BC547 conducts but transistor T4 does not conduct due to this the LED2 and buzzer does not operates. When the time of ON position of the instrument is over then the relay RL1 goes OFF. The load connected to the relay also goes OFF. Now the transistor T4 conducts and LED2 glows. Buzzer also rings after the set period.
PRECAUTIONS WHILE MAKING THE PROJECT
- Solder properly on PCB so that component does not get shorted.
- The relay used should be 12V relay and of good quality.
Check the component with meter before assembling the project.