The TV remote control controls the chandelier. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Телевидение

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The remote control (RC) can be used to turn on and off the lighting in the room where the TV is located. The author offers a chandelier control device with decoding of the command used. If decoding is not performed, as is sometimes done, the lighting may switch randomly when controlling the TV.

The encoding of commands used by manufacturers in TV remote control systems is quite diverse. In most cases, a command is transmitted as a sequence of several (ten or more) packets of pulses of varying durations, and information is carried not only by the pulses themselves, but also by the pauses between them. For example, a command from the remote control of a SAMSUNG SK-3338ZR TV contains 11-13 packs, each of which consists of 32 or 64 pulses with a filling frequency of about 40 kHz. The duration of pauses between pulses corresponds to 32 or 64 periods of the specified frequency. When you press the button for a long time, command messages are repeated with a frequency of approximately 9 Hz. The first three packets of the message do not depend on the transmitted command, but for even and odd button presses they are different - either short-long-short or short-short-long.

The remote control command codes for the above-mentioned TV are shown in the table. It uses the following designations: “0” - short pack; "1" - long pack; "|" - long pause. Short pauses are not indicated, since in all cases there is some kind of pause between the bursts. The parts of commands following the first three packets are given; they contain from 8 to 10 packets of pulses. In the table, these packets are aligned at the ends - as after receiving they are located in the shift register of the command receiver.

The author has developed a device that decrypts the SLEEP command; its diagram is shown in Fig. 1. The signal from the infrared photodiode VD1 is amplified by a specially designed DA1 microcircuit when turned on. its output (pin 10) of pulse trains of positive polarity (Fig. 2) arrives at the input of a node assembled on elements VT1, R1, R2, C6, DD1.1. This unit turns them into single pulses, the duration of which is slightly longer than the duration of the bursts [1]. Using transistor VT1 instead of the usual diode for such a unit reduces the load on the DA1 chip.

(click to enlarge)

Pulses from the output of element DD1.1 are inverted by element DD1.2 and, through the differentiating chain C7R3, are supplied to the one-shot on element DD1.4 and start it. The duration of the low-level pulses at the output of the monovibrator is about 1,2 ms, which corresponds to half the sum of the durations of the short and long bursts. The fall of pulses from the output of the one-shot (the difference in levels from log. 0 to log. 1) records information from the output of element DD1.1 into the first bit of the shift register DD2.1 and DD2.2 and shifts it towards increasing output numbers. If the next received burst was short, at the moment the monostable pulse ends, a log level is present at the output of element DD1.1. 0, which will be written to bit 1 of the register. Accordingly, with a long burst, the voltage at the output of element DD1.1 corresponds to log. 1, it will also be written to the register. As a result, after the end of receiving the command, information about its last eight packets will be generated in register DD2.1 and DD2.2, with the last one in digit 1. The voltages at the outputs of the microcircuits when receiving the SLEEP command are shown in Fig. 2 - in bits 1 and 4 of the register - log. 1, and in the rest - log. 0. Information about the duration of pauses is lost with this technique.

The node on element DD1.3 operates similarly to the node on element DD1.1 - while there are low-level pulses at the output of element DD1.2, the output of DD1.3 is a log level. 0, after the end of the command, a high logical level appears on it with a slight delay. This level difference is differentiated by the C12R8 chain and, in the form of a pulse of positive polarity, is supplied to the input of the AND-NOT element DD3.1. If the selected command has been accepted, this element is triggered and a short low-level pulse is generated at its output, switching the chain of triggers DD4.1 and DD4.2 to a new state. Signals from their outputs control the passage of pulses corresponding to the moment the mains voltage passes through zero and supplied to the input of the DD5.2 element. From its output, through elements DD5.1 ​​and DD5.3 and transistors VT2 and VT3, these pulses arrive at the control electrodes of triacs VS1 and VS2 (Fig. 3). The anode circuits of the triacs include lamps HL1-HL3 of the lighting chandelier. When the SLEEP command is issued multiple times, one lamp HL1, two lamps HL2 and HL3, or all three lamps are turned on in turn, then they all go out. The same result is obtained when closing the contacts of microswitch SB1. Elements R9, R10 and C13 suppress contact bounce and protect element DD3.1 from overload.

Shown in Fig. 3 unit for power supply and generation of pulses that trigger triacs is somewhat different from those described earlier by the author [2]. Instead of one of the diodes of the half-wave rectifier, a zener diode (VD5) is installed here, and pulses of rather long duration are supplied to the control electrodes of the triacs - about 0,75 ms, the middle of which corresponds to the moment the mains voltage passes through zero. The current supplied to the control electrodes during the action of the pulses is about 80 mA, which is enough to reliably straighten the characteristics of the triacs and turn them on without interference at the very beginning of each half-cycle.

With the pulse duty cycle indicated above, the current consumed to simultaneously turn on two triacs is on average about 12 mA. Such a current can well be provided by the quenching capacitor C14 of the power supply unit with a capacity of 0,68 μF. The pulsed nature of the main part of the current consumption leads to large voltage ripples on the filter capacitor C15. Their smoothing is provided by the DA2 integrated stabilizer. This is cheaper than, for example, using a C15 capacitor with twice the capacity.

The lighting control device is assembled on two printed circuit boards made of double-sided foil fiberglass laminate 1,5 mm thick (one contains the circuit elements of Fig. 1, the other - Fig. 3). The boards are designed for installation in the body of a pull switch installed in residential buildings under the ceiling.

The DA1 chip, together with its related parts, is covered with a thin copper shield soldered at several points to protect it from electrical interference.

The SB1 microswitch is equipped with a lever cut out of organic glass. A thin string is attached to its end, by pulling which you can manually control the chandelier to turn on.

The device can use microcircuits of the K176, K561, KR1561, DD3 series, which are interchangeable with the LA8 microcircuit of the indicated series. Transistor VT1 - any low-power silicon npn structure with a base current transfer coefficient h21E of at least 100, transistors VT2, VT3 of medium or high power with h21E of at least 80 with a collector current of 100 mA. Transistors VT4 and VT5 - almost any silicon low-power pnp structures. Triacs VS1 and VS2 - KU208 series in a plastic case with indexes V1, G1 or D1 or TS-106-10 for a voltage of at least 400 V (the index after the indicated designation is 4 or more).

Diodes VD2-VD4, VD6 - any low-power silicon diodes, zener diode VD5 - for a voltage of 12 V and an operating current of at least 20 mA.

As a DA2 microcircuit, you can use any domestic integrated stabilizer for -6V voltage - KR1162EN6, KR1179EN6 or imported ones - 79L06, 79M06, 7906 with any prefixes and suffixes.

All resistors are MLT of appropriate power, capacitors are KM-5, KM-6, K73-16 (C14) and K52-1B. It is permissible to install K50-35 or their imported analogues in place of oxide capacitors.

It is recommended to configure the device in the following order. First, on the board with parts according to the diagram in Fig. 1, connect the inputs of element DD5.2 to a common wire, and turn on any LED between the upper (according to the diagram) terminals of resistors R11 and R12 and the +6 V circuit. After that, to the contacts “+6 V” and “Common.” The board can be supplied with 6 V voltage from a laboratory power supply.

By pressing the rod of microswitch SB1, you should make sure that the LEDs turn on and off alternately. By sending the SLEEP command from the remote control to the photodiode VD1 (from a distance of 0,5...1 m and in not very bright lighting), you need to check the accuracy of the device’s operation and, if necessary, select the resistance of the resistor R4 to obtain the duration of the one-shot generated at the output of the one-shot element DD1.4. 1,1 pulses within 1,3...4 ms. This job is best done with a sweep oscilloscope. If it is absent, you can replace R220 with a variable resistor with a resistance of 51 kOhm in series with a limiting resistance of 4 kOhm and determine the resistance range in which the command is received. After this, a resistor with a resistance corresponding to the middle of this range should be installed in place of RXNUMX.

To check the board with the power supply (according to the diagram in Fig. 3) between its contacts “+6 V” and “Common.” you need to solder a 510 Ohm resistor of any power, connect the board to the network and, being careful (all its elements are under mains voltage), measure the voltage between the common wire of the board and the “+6 V” and “-6V” circuits. If they differ from the nominal values ​​by no more than 0,5 and 1 V, respectively, the boards can be connected to each other and the operation of the device assembly can be checked with loads in the form of lighting lamps.

Literature

1. Biryukov S. Suppression of impulses "bounce" of contacts. - Radio, 1996, No. 8, p. 47, 51.
2. Biryukov S. Triac power regulators. - Radio, 1996, No. 1, p. 44-46.

Author: S. Biryukov, Moscow

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