IR indicator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Measuring technology
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The infrared (IR) radiation indicator, or IR indicator, is used to determine the performance of IR emitters, and will also be useful in the repair of control panels (PU) of household appliances, paper presence / passage sensors in copiers, faxes, etc. . The human eye does not perceive the glow of such emitters, and the described indicator makes it possible to check their operation.
The scheme of the device is shown in Fig.1.
When the phototransistor VT1, which serves as an IR radiation sensor, is irradiated, it opens, and a positive potential is supplied to the current amplifier on transistors VT2-VT4, the load of which is the HL1 LED. The glow of the latter indicates the serviceability of the device under test. When checking the remote control of TVs, the indicator LED blinks at the frequency of the control pulses, and when checking the sensors for the presence of paper of copiers / faxes, it lights up constantly.
The indicator is powered by an external power adapter with an output voltage of 5 V. To increase the mobility of the device, batteries or, for example, disk batteries can be used as batteries, supplementing the circuit with a power switch. The experiment showed that the indicator works quite satisfactorily when powered from a 3 V source, when selecting the required sensitivity with resistor R1 and reducing the value of resistor R4 to 100 ohms.
Details. An optocoupler phototransistor from a faulty computer "mouse" was used as an IR radiation sensor. It must be carefully unsoldered and checked for serviceability (if necessary, determine the polarity of the connection) with a tester, illuminating with an incandescent lamp. Transistors any of the KT315, KT3102 series. LED type AP307 with any letter index. Capacitor type K50-16, and resistors type MLT-0,125.
Adjustment of the indicator consists in setting its sensitivity by selecting the value of the resistor R1. It should be noted that the indicator sensor reacts to bright solar and electric lighting, so setting too high sensitivity is undesirable. Ideally, the indicator should clearly show the operation of IR devices, not reacting to the radiation of lighting devices located in the room.
A drawing of the printed circuit board of the IR indicator is shown in Fig.2.
As the body of the device, the author used a box of "Tick-tock" dragees. It is transparent, so there is no need to drill holes for the LED and phototransistor.
Author: A.E. Molchanov, Rivne
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