Intelligent infrared remote control circuit design

Home appliances with infrared remote controls bring great convenience to our lives, but it is easy to get confused if there are too many remote controls. If there is an intelligent device that can identify, store and reproduce the control signals emitted by various infrared remote controls in the home, type infrared remote control, it would be great to use such a remote control to control all the electrical appliances in the home. To this end, the author tried to design an intelligent remote control with a microcontroller as the core, which is introduced below, hoping to serve as a starting point. The structure of the intelligent remote control is shown in Figure 1, which consists of a single-chip microcomputer, infrared receiving, infrared transmitting, display, storage, buttons and undervoltage indication. The circuit is required to be driven by two batteries. The microcontroller uses infrared remote control transmitter chip BA5048, and the working power supply voltage is 1.5~5V. Memory, LCD, and infrared transmitter all have ready-made 3V voltage products, while common infrared receiving integrated circuits (such as CX20106, HS0038) have a rated operating voltage of 5V. It is difficult to find a ready-made low-voltage infrared receiver. Considering that the receiving distance of the smart remote control is only a few centimeters and the power requirements are not high, the author designed the low-voltage infrared receiving circuit shown in Figure 2. Among them, V is the receiving tube; R3, R4, and V1 constitute the inverting amplifier; V2, R5, and C2 constitute the filter, which filters out the 38kHz carrier signal in the control encoding signal; R6, R7, and V3 constitute the shaper; C1 and C3 are Coupling capacitor; R2 is the current limiting resistor, which protects V from damage when the input signal is strong; R16 and V10 form an electronic switch. In the recognition "learning" state, a low level is sent to the point to turn on V10 and the circuit starts. Work, in the "control" state, send high level to the point, V10 is cut off, and the power is turned off. The working power supply voltage range of this circuit is 1.5~5V. At 3V, the quiescent current is 0.42mA, and the effective distance is 40cm. The "Reset" key control encoding waveform of the Z654-8A color TV remote control measured using this circuit is shown in Figure 3 (the output waveform is opposite to the envelope waveform of the transmitted encoding). The smart remote control also has an under-voltage detection function, and the detection circuit is shown in Figure 4. During detection, the microcontroller sends high level to point C and low level to point B. V9 is turned on and point is low level. The point voltage changes as the Vcc voltage changes. When the Vcc voltage is high enough, the point voltage is enough to turn on V7, and the point outputs a low level and is sent to point A. When the microcontroller detects the low level at point A, it confirms that the power supply voltage is normal. If the voltage is insufficient, V7 is cut off and the point outputs high level. The microcontroller starts the alarm function and sends low level to point D and high level to point C. V8 and V4 are turned on and the buzzer sounds an alarm to remind the user to replace it in time. Battery. The buttons of the single-chip computer BA5048 are composed of a 6×3 matrix, and with the encoding diodes, 63 kinds of button encodings can be realized. This remote control only needs 40 buttons to meet the control requirements of all home appliances. There are 3 function keys including the control key CANCEL, the recognition and learning storage key LEARN, and the macro definition function key MACRO; 8 household appliance number keys for recognition and learning input, numbered DEV1 to DEV8; 10 TV channel selection keys N o0 ~No9; 19 other household appliance function control keys S1~S19. If you want the circuit to work in the recognition learning state, just press the "LEARN" key and the corresponding household appliance number key to record the control code waveform of the household appliance remote control. If an electrical appliance has many control functions, you must also press S1 and other control keys to distinguish the different functions of the electrical appliance. After the recording is completed, the smart remote control can be used to replace the remote control of the household appliance. When using it, just exit "LEARN" and press the control key "CANCEL" and the relevant numbered function keys. To use the macro definition function, press the "MACRO" key in the "Control" state, and then select the required numbered function key to achieve a series of remote control. The software programming of the smart remote control is very simple. You only need to follow the instructions for use of the selected microcontroller and the above circuit principles, and you can quickly program it. I won’t go into details here.