Control AC Loads Wirelessly with This DIY RF Relay Switch

This wireless AC load control system operates by transmitting and receiving radio frequency signals at 433MHz to toggle a mechanical relay. The transmitter circuit uses a push-button switch to send a signal through the TX2H-433-64 RF module, utilizing a simple wire antenna for wireless propagation. On the receiving end, the RX2A-433-64 RF module captures the incoming radio waves and feeds the resulting electrical pulses into a CD4027 dual J-K flip-flop IC (IC1A). The J-K flip-flop acts as a digital memory element that toggles its output state with each received button press, providing a reliable on/off toggle mechanism rather than momentary action. Because the integrated circuit outputs minimal current, the signal passes through a BC107 transistor (T1) and a 2N2219 transistor (T2) configured to amplify the control current sufficiently for driving the SPDT 5V relay. When energized, the relay's electromagnetic coil mechanically switches its internal contacts to open or close the connected AC circuit pathway, physically isolating the low-voltage logic circuitry from high-voltage mains. Additionally, a 1N4007 diode (D1) is placed in reverse bias across the relay coil to safely suppress harmful voltage spikes generated by magnetic field collapse when the relay turns off. Capacitors such as the 220µF and 1µF components help smooth voltage fluctuations and stabilize the power supply rails across the board, while LED1 provides a visual indication of the system's operational status.