Infra-Red Remote Tester

This little circuit is
invaluable for quick go/no-go testing of just about any remote control
transmitting infra-red (IR) light. The tester is battery-powered, built
from just a handful of commonly available and inexpensive parts, and
fits in a compact enclosure. Schmitt trigger gate IC1f is used as a
quasi-analogue amplifier with, unusually, an infra-red emitting diode (IRED)
type LD274 acting as the sensor element. An R-C network, C1-R2, is used
at the output of the gate because all IR remote controls transmit pulse
bursts, and to prevent the output LED, D2, lighting constantly when day-light or another continuous source of IR light is detected.

Picture of the project:

Circuit diagram:

Parts Layout

PCB layout:

Cased project:

This creates a useful ‘quick test’ option: point the tester at direct daylight, and the indicator LED
should light briefly. The sensitivity of the tester is such that IR
light from remote control is detected at a distance of up to 50 cm. The
circuit is designed for very low power consumption, drawing less than 1
mA from the battery when IR light is detected, and practically no
current when no light is detected. Hence no on/off switch is required.
The construction drawing shows how the tester may be ‘cased’ using a
small ABS case from Conrad.


R1,R2 = 10MW
C1 = 10nF

D1 = LD274 (Siemens)
D2 = LED, 3mm, low-current
IC1 = 74HC14

Bt1 = 3V Lithium cell with solder tags, e.g.type CR2045 (560 mAh)

Author: W. Foede
Copyright: Elektor Electronics

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