LLZ the principle of infrared, infrared remote control has been widely used in home appliances and industrial control system, understand their work principle and performance, further made the infrared remote control system, also is not difficult.
characteristic of infrared eye can see the visible light wavelength, according to arrangement, in turn (from long to short) for the red, orange, yellow, green, cyan, blue, purple, as shown in figure
1. Can be seen from the graph, the red light in the wavelength range of 0.62μm ~ 0.76μm, longer than the red wavelength light is infrared. Infrared remote control is the use of wavelength of 0.76μm ～1.5μ m near to transmit a control signal. Mainly Feature of Infrared is that it does not interfere with other electrical equipment, it will not affect the surrounding environment. the Circuit debugging simple, if the transmitted signal code, can realize the function that multi-channel infrared remote control.
2 Infrared remote control system of infrared emitting and receiving
people see consists of transmitting and receiving the two part. The emission component parts for infrared emitting diode, it emits infrared rather than visible light, as shown in figure
2.Common infrared wavelengths emitted from the light emitting diode is about 940nm, the shape and the ordinary 5 mm light emitting diode is the same, but different colours. In general there are transparent, black and dark blue three. Method for judging the quality of infrared light emitting diodes is same with ordinary diode.emitting power of the infrared light emitting diodes is about 100mW. Luminous efficiency with a special instrument for determination, on amateur conditions, can rely on the experience with the distance of roughly determination method. The infrared receiving tube receiving circuit is a photosensitive diode, when used for infrared receiving diode reverse bias voltage is applied, it can work normally and obtain high sensitivity.How it works: infrared photosensitive resistance is actually a resistance.in a high impedance state is close to the 6K when not have infrared lighting. completely avoid the light may not only, The mainly parameter of Infrared LED(receiving module) as follows:
work voltage：4.8～5.3V
work currently：1.7～2.7mA
receive frequency：38kHz
peak value of wavelength：980nm
static state of output：High level
low level of output：≤0.4V
high level of output：VDD voltage
The infrared receiving diode are generally circular and square two. Because the transmitting power of the infrared light emitting diodes are small, weak signal received by the infrared receiving diode, so the receiver will increase the high gain amplifier circuit.