Single-channel remote control switch - power supply circuit - circuit diagram - Huaqiang Electronic Network

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This paper discusses a remote control switch that boasts a remote control distance greater than 30 meters, with no directional limitations, capable of penetrating walls, ensuring stable operation, and featuring a compact design. By incorporating this circuit into the power supply circuit of household appliances, they can be equipped with remote control functionality. Below is a detailed description of its circuit principle and manufacturing process.

Firstly, the circuit principle: 1. Remote Control: As shown in Figure 1, a multivibrator comprising transistors T5 and T6 generates a square wave signal, which serves as the input for the 240MHz–260MHz RF signal produced by the inductor three-point oscillator formed by T7. This RF signal is pulse-modulated and radiated from the printed antenna on the board into space. The battery used in the remote control is an A23-type 12V battery, providing power for up to six months and is easy to replace. 2. Receiving Circuit: As illustrated in Figure 2, the UHF receiving and demodulation circuit consists of T1, L1, C0, etc. Adjusting C0 can optimize the receiving circuit and the remote controller's positioning. The demodulated pulse signal is sent through R5 and C5 to operational amplifier A1A for comparison and amplification. The output signal passes through the C7, D2, and D3 voltage-doubling circuits and is sent to operational amplifier A1B for peak comparison. When the 6-pin inverting terminal detects a peak pulse exceeding the threshold voltage set by the 5-pin, the 7-pin outputs a low-level signal, triggering the bistable circuit made up of T2 and T3 to flip, thereby controlling T4 to either conduct or cut off, thus pulling or releasing the relay. The integral delay function of R11 and C8 effectively suppresses and eliminates interference from various short-duration sharp pulses (such as lightning or fluorescent lights).

Secondly, the production and debugging process: 1. The remote control circuit is relatively straightforward and generally functions without requiring additional debugging, but care should be taken when selecting the transmitting tube T7 and the inductance. The amplification factor of T7 can be approximately 80. 2. The receiving circuit components are chosen based on the parameters in the diagram. The amplification factor of T1 is about 90, and the relay is a micro-relay of 12V. Other components do not have any specific requirements. 3. During debugging, pressing the remote control switch, connect the negative pole to the A1A output pin of the operational amplifier with a high-impedance earphone, and then adjust C0 using a non-inductive screwdriver until the "beep" sound in the earphone reaches its maximum. Once the commissioning is complete, the transmitter and receiver are installed in a suitable housing. In use, the normally open contacts of the circuit relay are connected in the power supply circuit of the appliance to be controlled. Pressing the remote control activates the relay, turning the appliance on; pressing the remote control again turns the appliance off.

Additional notes: The design of this remote control switch is particularly suitable for applications where compactness and reliability are critical. The integration of the RF module ensures robust performance even in environments with multiple electronic devices. Future iterations may explore the addition of encryption features to enhance security against unauthorized access. Additionally, improving the energy efficiency of the remote control could extend its operational lifespan further.