Remote control indicator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / infrared technology
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The proposed indicator will allow you to timely detect the failure of the IR remote control (RC) of a household appliance or check it after repair. The indicator scheme is shown in fig. 1.
(click to enlarge)
The IR signals emitted by the remote control (packages of code pulses) are received by the BL1 photodiode connected to the input of the logic element DD1.1 serving as an amplifier. Further, the signal through the isolation capacitor C1 is fed to the threshold device, the role of which is performed by the element DD1.2. The response threshold is set using a resistive voltage divider R2-R4 so that each received IR pulse leads to the appearance of a high logic level pulse at the output of the DD1.2 element.
A multivibrator is assembled on the elements DD1.3 and DD1.4, the operation of which is allowed only at a high logic level at the output of the element DD1.2. Since the duration of the pulses here is very small, the multivibrator only "stretches" them, essentially operating in standby mode. As a result, each received command is accompanied by clicks in the sound emitter BF1 and LED flashes HL1. However, if the tuning resistor R3 is incorrectly adjusted or a very long sequence of IR pulses is received (which, like the absence of pulses, usually indicates a malfunction of the remote control), the multivibrator goes into self-oscillating mode. The glow of the HL1 LED and the sound become continuous.
The indicator is assembled on a printed circuit board made of foil fiberglass, shown in fig. 2, and place it together with a GB1 battery with a voltage of 6 ... 9 V in a suitably sized case. Photodiode FD-256 can be replaced by any IR range. The operation of the indicator was also tested with the SFZ-2 photoresistor installed instead of the photodiode. Transistors VT1, VT2 - KT315 series or other silicon low-power npn structures. Sound emitter - piezoelectric ЗП-3, ЗП-5 or ЗП-18.
When setting up the indicator, close the receiving window of the BL1 photodiode with an opaque shutter and set the trimming resistor R3 engine to the lower position according to the diagram. The HL1 LED should be lit, and sound should be heard from the BF1 emitter. If the tone of the sound does not suit you, select the value of the resistor R6. Then, using the trimmer resistor R3, turn off the LED and stop the sound. It remains to remove the shutter, direct a known-good remote control to the BL1 photodiode and make sure that clicks are heard when any command is given, and the HL1 LED flashes.
Author: G.Sauridi, Ryazan
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