When a remote control signal is received, the energy stored in C2 drives the emitter diode. At the same time, Q1 switches on briefly to allow the battery to recharge C2. The green LED shows that the circuit is transmitting; and the yellow LED confirms that C2 has been topped-up.
There is unwanted IR radiation in both daylight and tungsten lighting.
To minimize its effect use an opaque housing and do not make the opening too large. (Try a horizontal slot measuring 2 cm X 1.5 cm.) Shade the receiver diodes by mounting them side-by-side a few centimetres deep, inside the case. The depth of shading requ