A short range Radio Remote system can be implemented using the VHF radio remote control modules VG40 T and VG40 R. These are compact sealed VHF Transmitter and Receiver module pair works without antenna. Its range is 15-20 meters. These modules find various applications in Wireless door chime, Toy controlling, Security system etc. Here explains the design of an Appliance On / Off switch using the radio waves.
VG40 T is the transmitter module having a size of 34 x 29 x 10mm. It works with 9 volt PP3 battery and by pressing the switch, it transmits 315 MHz signals. The Transmitter is pulse transmitting and complies with FCC standard. Stand by current of the transmitter is 5 uA.
VG40 R is the receiver module measuring 45 x 21 x 13 mm size and requires + 3 volts for operation. Its receiver end is designed to receive the 315 MHz signals from the transmitter and is immune to other frequencies. Receiver stand by current is 300uA.
Relay control using VG 40 T / R Module
Transmitter module VG40 T is used to activate the Relay driver circuit to turn On / Off the load. When the push switch is pressed, Transmitter gets 9 volt from the battery and it sends a positive signal from its output. The signal is in the 315 MHz frequency that can pass through the air up to 20 meters without an aerial.
In the receiver section, VG40 R receiver module is used to receive the signals from Transmitter. When it receives the signal, it sends a positive pulse to the base of T1 through R1 and D1. This triggers T1 and it conducts. Activation of T1 triggers IC1 which is a short duration monostable. Output pulse from IC1 clocks IC2 which is the Decade counter wired in the Toggle mode. That is, its Q1 and Q2 outputs turns high and low alternately since the Q3 output is shorted to the Reset pin 15.When Q1 turns high, Q2 turns low and vice versa. When Q2 turns high, T2 triggers and Relay energize to connect the load through its common and NO contacts. By pressing the switch again, the Load can be switched off .Red LED indicates the Off position.
VG 40R module requires 3 volts, so 3.3 volt Zener is used to regulate the voltage to the receiver module.3.1 V and 3.3 V Zener diodes are easily available. VG 40T and VG 40R pair cost Rs.100.
Use thin wires to connect the Receiver module with the remaining circuit. Enclosing the Transmitter in a Non metallic case like plastic box will increase its sensitivity.