This device will help to check and repair the device, which based on the use of infrared (IR) region of the electromagnetic spectrum - remote controls for household appliances, sensors paper present in printers, copying and facsimile machines. Being held close to the source not perceived by the human eye, the infrared rays, it will give a signal about their presence.
Scheme of the indicator is represented in Fig. 1.
When irradiated with infrared rays sensitive to them the phototransistor BL1 opens. Flowing through it in this case current, after amplification by transistors VT1-VT3, enough to light a led HL1. The illumination of the past and witness the performance check the source of IR radiation. If you send a good indicator panel remote control of the TV and press any button, the led HL1 will blink with the frequency of the emitted pulses. The IR radiation sensors of the presence of paper continuous, so the led will light steady.
5 V to power the indicator can be obtained from the network adapter. Current consumption is very small. If you want to make the device is offline, you can to feed it from the battery of two to four cells or batteries, not forgetting to include the switch. When reduced to 3 In the supply voltage may need to replace the resistor R4 to the other, par value 100 Ohms.
Drawing of the PCB of the indicator shown in Fig. 2. It is placed in the body - the package of jelly beans "Tick-tock". The packaging is transparent, so drilling into it the holes for the led and phototransistor is not necessary.
The phototransistor that is sensitive to IR radiation, carefully fed from faulty computer mouse. Before you install the indicator it using ohmmeter check and, if necessary, determine the pin assignment. When the correct polarity of the connection to the device resistance plot collector-emitter serviceable phototransistor in the dark must be very pain-PWM (over 1 MW), and when lighting a conventional bulb will decrease many times.
Transistors KT315B you can replace any of the series KT315, KT3102 and led ALB - other domestic or import of suitable size and color glow.
The required sensitivity of the indicator is achieved by selection of the resistor R1. Not you should install it too high - the unit will react to normal daylight or electric light. Sufficiently accurate fixing of IR radiation on the distance of a few centimeters from its source.
Author: A. Molchanov, Rivne, Ukraine