[Daily circuit diagram] 2, infrared remote control circuit principle design and analysis of "Turn + interpretation"

Landlord said: This is mainly about an infrared remote control circuit principle and design, part four is the focus, with the circuit diagram to illustrate the specific process-receive, count, meet the conditions trigger control circuit!

From elecfans:http://www.elecfans.com/article/88/131/198/2015/20151215394306.html

First, overview:

　　Infrared remote control of the emission circuit is the use of infrared light emitting diode to emit modulated infrared light wave, infrared receiving circuit by the infrared receiver diode, transistor or silicon photovoltaic cells, they will be emitted by the infrared emitter of the infrared to the corresponding electrical signal, and then send the amplifier . Remote control technology, also known as Telecontrol technology, refers to the realization of the controlled target of remote controls, in the industrial control, aerospace, household appliances in the field of wide application. Infrared remote control is a wireless, non-contact technology, with strong anti-jamming ability, reliable information transmission, low power consumption, low cost, easy to realize and other notable advantages, many electronic equipment, especially household appliances widely adopted, and more and more applications to computer systems.

Second, features:

The spectrum is outside the red light, the wavelength is 0.76~1.5μm, and the wavelength of the red light is longer, so the light is called infrared. Infrared remote control is the use of infrared to transmit information of a controlling system, infrared remote control (advantages) have anti-jamming, circuit simple, coding and decoding easy, low power consumption, cost advantages, the current almost all video and audio equipment support this control mode.

Third, the composition:

Infrared remote control system Structure Infrared remote control system is mainly divided into modulation , transmission and reception of three parts, 1 shows:

Figure 1 Infrared remote control system

3.1, modulation of the infrared remote control of the transmission of data using modulation, that is, the data and a certain frequency of the carrier "and" operation, which can improve the emission efficiency and reduce power consumption . Modulation carrier frequency generally between 30khz to 60khz, most of the use of 38kHz, duty-free 1/3 of the square wave, 2, which is used by the transmitter side of the 455kHz Crystal determined. On the transmitter side to the Crystal Oscillator integer division, the frequency division coefficient is generally taken 12, so 455khz÷12≈37.9khz≈38khz.

Figure 2 Carrier Waveform

3.2, the Launch System currently has many kinds of chips can achieve infrared emission, according to the choice of different types of coding. As the launch system is generally battery-powered, which requires the chip power consumption is very low, most of the chips are designed to be in hibernation, when the button is pressed to work , which can reduce the power consumption of the chip used by the crystal oscillator should have enough resistance to physical impact, not the use of ordinary quartz crystals, Generally choose ceramic resonator, ceramic resonator accuracy is not high quartz crystal, but usually a little error can be ignored . Infra-red infrared light Emitting diode (LED) emitted, infrared light-emitting diode internal material and ordinary light-emitting diodes, when applied to the two ends of a certain voltage, it emits infrared rather than visible light .

Figure 3a Simple drive schematic 3b shooting output drive circuit

　3a and Figure 3b is the driving circuit of the LED, Figure 3a is the simplest circuit, the selection of components should pay attention to the transistor switch speed is fast , but also to take into account the LED forward current and reverse leakage current, generally through the LED's maximum forward current is 100mA, the larger the current, The higher the waveform intensity of its emission. Figure 3a Circuit has a point of defect , when the battery voltage drops, the current flowing through the LED will be reduced, the emission waveform strength decreases, remote control distance will be smaller. The emitter output circuit shown in Figure 3b can solve this problem, Two diodes to the three-stage tube base voltage clamp at around 1.2V, so three-stage tube emitter voltage fixed around 0.6V, emitter current IE basically unchanged, according to Ie≈ic, so the current flow through the LED is basically unchanged, so as to ensure that when the battery voltage is reduced can also guarantee a certain remote control distance.

* Four, actual combat:

Infrared remote control Switch circuit working principle ~

　　

Figure 4 Infrared remote control switch circuit diagram

The power supply circuit consists of power switch s, Buck capacitor cl, resistor RL, Zener diode vs, Rectifier diode VD and filter capacitor C2.

1. The remote receiving circuit consists of a special component of the infrared receiving head, ICL and resistor R2, capacitor C3.

2. The counter circuit consists of a serial counter integrated circuit IC2 and a resistor R3, a capacitor C4.

3. The control execution circuit consists of resistor R4, R5, transistor V, and Crystal network Vt.

　　

　　(process) TV and other appliances used by the infrared remote control, about 10 sets of remote code pulses per second, each group of remote coded pulses between a certain interval. The infrared receiving head ICL receives the remote control transmitter to transmit the infrared remote control signal and carries on the demodulation after the output, after R2, C3 integral (filtering each group of pulses in the encoding information), increases from the IC2 1 feet, as the lC2 Count Pulse (about 10 pulses per second). 1c2 after receiving 8 pulses (about 0 8s), its 6 feet become low or high, so that V and VT on or off, the load (electrical equipment) work power is connected or disconnected.

Five, Component selection:

RL-R5 Select "/4w Carbon Film resistor or metal film roar resistance device.

C1 Select a polyester capacitor or cbb capacitor with a voltage resistance of 400V or more; C2-C4 aluminum electrolytic capacitors with a pressure-resistant value of 16V are selected.

VD chooses 1n4007 type Silicon rectifier diode.

VS Select 1/2w, 6 2v silicon regulator diode.

V uses 59015 or 58550, C8550 type Silicon pnp transistor.

VT Select 3 A, 400V double ask thyristor.

ICL selection of TV with miniature integrated package infrared receiver head (when using the hood or with a translucent filter), IC2 selection of CD4024 type 7-bit binary serial counter integrated circuit.

Six, circuit debugging:

After the circuit is installed, connect the voltage and load, change the resistance of R5, so that the AC voltage between the TL pole and T2 pole of VT is below 3V.

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[Daily circuit diagram] 2, infrared remote control circuit principle design and analysis of "Turn + interpretation"