lights or other electronic appliances of another room while sitting on your bed.
The circuit shown here is very easy to build and using very low cost and commonly available components. The circuit has also a good range of upto 20 meters. A relay switch is used at the output of the circuit, which can be connected with the appliances to make them switch ON/OFF. The whole project contains two parts, which is an FM transmitter and a RF receiver. For good results use a good quality FM transmitter with the circuit. We have used our best FM transmitter circuit with 9V battery as a transmitter with this receiver and it was working well.
The receiver circuit only detects the RF signals so there is no need of microphone with the transmitter. The receiver circuit can be operated with 3V to 12V DC. The current consumption of the circuit is very low and in standby mode the circuit drains only 400uA due to which it is ideal to be operated with batteries.
As you know the circuit is RF based so it requires some tuning for the first time. After building both parts of the circuit i.e. FM transmitter and the receiver circuit attach 80cm antennas (telescopic or wire) at both units and first check if the FM transmitter is working properly by tuning it on any good FM receiver. After that tune the transmitter on the RF receiver by adjusting the 1-35pF trimmer in the receiver circuit until the proper transmitter signal is received. Now slowly make distance between the transmitter and the receiver and adjust the trimmer at both sides. The sensitivity of the receiver circuit can be adjusted with the 220K variable resistor. Slowly adjust it for the maximum sensitivity by placing the transmitter many meters far from the receiver. It is suggested to use a slightly big variable resistor. With big variable resistor the circuit can be easily tuned to its maximum sensitivity. After tuning the circuit with a big variable resistor you can use a fixed resistor.
The Coil L1 in the receiver circuit is a hand made air cored coil having 6 turns of 24# enameled wire wound closely on a 5mm form.
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Radio controlled switches are very common now days. Unlike an infrared controlled switch a RF (Radio Frequency) switch also works if there are any type of obstacles between, therefore you can control your home appliances across the wall or in another room. For example you can switch your fan,
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