Infrared remote control is a wireless, non-contact control technology with strong anti-interference ability, reliable information transmission, and low power consumption. Infrared remote control does not have the ability to control objects through obstacles.
VS1838 / BHS0038 infrared receiver head, integrated monitoring, amplification, filtering, demodulation and other series of circuits to process the output baseband signal. In fact, HS0038 and VS1838B are no different, but the performance is better than 0038!
1. Infrared sensor principle
The original signal is a "0" bit of data or a "1" bit of data, and the so-called 38K carrier is a square wave signal with a frequency of 38K. The modulated signal is the final waveform we emit. We use the original signal to control the 38K carrier. When the signal is data "0", the 38K carrier is sent out without reservation. When the signal is data "1", no carrier signal is sent.
In order for HS0038B to recognize the 38K infrared signal, the 38K carrier must be greater than 10 cycles, which limits the bit rate of the baseband signal of infrared communication must not be higher than 3800, then if the signal output from the serial port is used directly With 38K modulation, the baud rate cannot be higher than 3800.
What we have learned is the NEC agreement, its characteristics are:
1. 8-bit address and 8-bit instruction length
2. Two transmissions of address and command (to ensure reliability)
3. The PWM pulse position is modulated to represent "0" and "1" with the duty cycle of the infrared carrier wave emitted
4. The carrier frequency is 38KHZ
5. The bit time is 1.125ms or 2.25ms
NEC code bit definition: one pulse corresponds to a continuous carrier of 560us, a logic 1 transmission requires 2.25ms (560us pulse + 1680us low level), and a logic 0 transmission requires 1.125ms (560us pulse + 560us low level)
The data format of the NEC remote control command is: synchronous dock, address code, address reverse code, control code, and control reverse code. The synchronization code consists of a low level of 9ms and a high level of 4.5ms. The address code, address inverse code, control code, and control inverse code are all 8-bit data formats. Send in the order of low bit first, high bit last. The inverted code is used to increase the reliability of transmission.
Second, the circuit design
Let's share a volume amplification and adjustment circuit designed with an infrared receiver:
- Amplifier MCU STC15W204S
- Power amplifier class D audio amplifier TPA3110D2
- Power amplifier volume control-LM4811 105mW headphone amplifier
- Infrared remote control volume-infrared receiver tube VS1838B
Schematic diagram: (The infrared sensor output needs to be connected to a pull-up resistor to prevent external interference during no-load)
PCB design: (infrared remote control to adjust the output volume)
program:
Original article, first published on allchipdata.com, free download of circuit and program resources: http://www.allchipdata.com/archives/965