Construction Clues and Testing
The construction is pretty simple as the circuits involved hardly contain any components. Begin by constructing the control circuit first, by inserting and soldering the IC first, followed by the transistor, relay etc. neatly over the given piece of general PCB. Interconnect their soldered points with the help of the given schematics. Similarly finish building the transmitter circuit with the help of the given circuit diagram. Integrate the control circuit with the FM circuit board (procured readymade) to conclude the construction of the whole system.
Once you complete building and the integration process of the above circuits, its setting and testing may be done in the following manner:
Initially do not connect an antenna to the receiver circuit. Connect and apply a 12 volt DC supply to it and the control circuit board. Due to the typical regenerative “hissing” of the FM receiver, you may find the indicator LED light up and the relay energized. Adjust the preset gradually until the LED just shuts OFF and the relay deactivates. Keep the circuit switched ON in that position.
Now, connect a 3 volt cell (button type) to the transmitter circuit and switch it ON by pressing its push-to-ON switch. Keep it depressed (by putting a heavy object over the switch). It should hopefully start transmitting the modulated signal in the air.
Go back to the receiver circuit; carefully start adjusting the gang condenser. At a particular point on the dial, the receiver should pick the transmitted signal to light up the LED and activate the relay. Fine tune it until the LED produces maximum illumination. Since the receiver does not have an antenna during this instant, you can be sure that the received signal is from your transmitter only and not from the usual FM broadcasts.
Switch OFF both the units. Connect a flexible wire of around 12” as an antenna to the receiver circuit. The transmitter will also need an antenna; an inch of wire will quite suffice.
This wraps up the setting as well as the testing of this wireless remote control circuit.
House the receiver circuit inside an appropriately sized plastic box, allowing the mains cord and the antenna out of the box. Also, make proper arrangements over the box for the fitting of the external socket and the LED.
The transmitter circuit should be also enclosed carefully inside a small match-box sized plastic box. The box should have ample space to hold the entire circuit and the 3 V button cell. Also, fix and connect the tiny micro switch at a suitable position to enable easy handling and operation.
The receiver unit may be placed in a suitable position with the respective load connected to it. You may test its efficiency by toggling the button of the transmitter from a distance of around 40 meters away and verify whether the receiver is responding to it or not. Check its consistency by doing it from different corners of your house.