Simple infrared remote control light switch circuit

In daily life, "turning off the lights when you are not around" is easier said than done. Often, because the light switches are far away, people are too lazy to turn off the lights even when they don't need lighting temporarily, and leave them on until they go to bed or go out. This situation is very common, resulting in a large amount of energy waste.

If the light can be turned on and off by remote control, it will be easy for people to develop the good habit of turning off the light at will. However, considering the cost of the remote control device, it is difficult to popularize and promote it. Here, after repeated experiments, I proposed a simple infrared remote control light switch circuit scheme (Figure 1): the remote control transmitter can be replaced by any infrared transmitter at home, and no special production is required; the remote control receiving electrical appliance uses ordinary diodes and triodes and other components, which are low-cost and easy to make, and each set only costs about 9 yuan.

Circuit Principle The schematic diagram of the simple light remote control switch circuit is shown in Figure 2. The entire circuit can be divided into three parts.

1. In Figure 3, IR is the infrared remote control receiver. When no infrared signal is received, pin 1 outputs a high level. When an infrared signal is received, pin 1 outputs a series of low level pulses.

2. In Figure 4, R4, C2 and R7, C3 form two integration circuits, and VT4, VT5, and K form a relay control circuit.

3. In Figure 5, the light emitting diode is used as an indicator light for the circuit to work.

The initial state of the lamp during normal operation or after power-on is that VT1 is on, VT2 is off, VT5 is off, and relay K does not work.

Short press the remote control button (less than 0.5s). In this short period of time, because the capacity of C3 is much larger than that of C2, the potential at point B quickly rises to a high potential (about 1V), while the potential at point A rises less than 0.6V. Therefore, VT3 cannot be turned on, and only VT2 is turned on. In this way, point C is at a high potential, VT5 is turned on, relay K is activated, and its contacts K-1 and K-2 are turned on at the same time, and K-2 is connected to the power supply of the appliance.

At this time, even if IR no longer receives a signal, VT5 remains turned on because the power supply provides bias to VT5 through R11, and K continues to be attracted, achieving the purpose of turning on the light by short pressing the remote control button.

When the remote control button is pressed for a long time (more than 3 seconds), IR outputs a low-level pulse, causing VT1 to output a high-level pulse, which is rectified by VD1 and sent to points A and B for integration processing, eventually making the potential at point A greater than 1V (measured to be about 1.3V), VT3 is turned on, point D is high level, VT4 is turned on, and point C is low level, causing VT5 to be cut off, K to be released, and K-1 and K-2 to be disconnected, achieving the purpose of turning off the light by pressing the remote control button for a long time. After releasing the remote control button, IR no longer receives infrared signals, C2 and C3 discharge, VT2 and VT3 are cut off, and the circuit enters the waiting state again. Only when the remote control button is pressed again, the circuit will act again and repeat the process of turning on the light by remote control.

Circuit Testing

Step 1: Connect a light emitting diode and a 5.1k resistor at K-2 instead of the light bulb, see Figure 6.

In a room without a TV, use a Konka TV remote control as a switch remote control. Within 12 hours, the diode can work normally.

Step 2: In the hall with Konka TV, continue to use Konka remote control, but when the TV is turned off with the remote control, the light on and off also changes. The work will not work when it is 8m away from the remote control. In other words, the remote control distance is about 8m, and its activation may affect the normal operation of other devices using the remote control.

Step 3: Use different remote controllers (we used Midea air conditioner, motorcycle switch, common infrared transmitter, etc.) to control the work, and encounter the same phenomenon as in Steps 1 and 2. This shows that the work can be controlled by any remote controller.

Step 4: After making preparations to insulate the work, connect the diode and resistor to a desk lamp instead and use AC power, as shown in Figure 7.

Repeat the above three steps, and the resulting phenomenon is similar to the above.

Shortcomings and improvements of the work and related explanations

1. From the above test, it can be seen that the actual object made by this design may cause confusion in life - turning off the TV also turns off the lights, and turning off the lights also turns off the air conditioner. Therefore, an infrared transmitter and a corresponding receiver must be specially designed, but this greatly increases the cost. One solution is to use the air conditioner remote control or the buttons in the TV remote control that will not affect the status of the TV at this time where there is a TV.

Others are similar.

2. This work is made by welding. On the one hand, it is to show that ordinary people can also make it. On the other hand, the production cost will be lower for small batches. On the other hand, it shows that this solution is very easy to implement.