THE SPECIALITIES OF PROJECT
The Fax machine is put ON when any document is been sent/received. When Fax machine is kept ON, power is supplied to the heater element and shortened its life. This circuit avoids this problem.
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 project one IC555 and 2 transistors BC547 are used. Its working system is very simple. When this circuit is connected with telephone line. The ringtone signal from the telephone line gets rectified, filter and goes to the base of transistor T1 BC547. The transistor starts working and necessary voltage for triggering goes to the Pin N0.2 of IC555. High Output is available at Pin No.3 of the IC. Now base of transistor T2 BC547 gets voltage. Now this transistor conducts and relay R1 connected to its collector is put ON. The ON period of RL1 depends upon the C5(1000MFD) and R4(100k). The component in the circuit give the time period of the 100sec. The instrument(fax) will be put OFF after 100sec but when we send the message through fax then switch S1 is kept in ON position/. In this condition the relay is bypassed and message goes onward.
Considering the circuit we give 9V supply for 24hours to the fax machine to avoid unnecessary electric consumption.
PRECAUTIONS WHILE MAKING THE PROJECT
- Keep the PCB clean and avoid any shorting.
- Use the IC base for IC.
Use good quality On/OFF switch and relay in the circuit.