Diagram Plus guide

The designer of this circuit had fitted two (waterproof) loudspeakers in his bathroom and connected them to the stereo system in the living room via a long cable. Naturally, this promptly led to the desire to be able to use the remote control unit from the bathroom. Commercially available extension sets for this purpose were judged to be unsatisfactory, primarily because they require an additional IR transmitter diode to be fitted in front of the amplifier. Although the repeater shown here requires a length of coaxial cable, it provides a simpler, and above all more reliable, solution to the problem. The signal transmitted by the remote control unit is received by IR receiver IC2, and the (nearly) open-collector output of T1 is connected to the RC5 bus of the stereo system.

This proved to work excellently with Philips equipment, and it will probably also work with equipment from other manufacturers with a few small modifications. Voltage regulator IC1 is used here to allow the supply voltage to range from 8V to 30V, and diode D1 provides protection against a reverse-polarity supply voltage connection. A nice side benefit arose from the fact that the loudspeakers in question (Conrad models) have transparent cones and protection grilles with rather large openings. This made it possible to fit the tiny circuit, which was built on a piece of prototyping board, to the frame of one of the speakers, behind the cone. The whole arrangement is thus hidden, but the remote control still works perfectly if it is aimed towards the speakers.