In this circuit we use the output signal from a standard IR receiver (IC1 in the schematic of Figure 1) to drive a miniature loudspeaker. The IR receiver from Vishay used here is available for various frequencies ranging from 30 to 56 kHz. A large number of IR remote controls operate according to the so-called RC5 protocol that uses a frequency of 36 kHz. In our prototype we used a TSOP4836; and as the part number suggests, it is intended for 36 kHz operation. However, it will also ‘work’ at other frequencies, if they are not too different.
The signal at the output of the IR receiver is at too high a frequency to generate an appropriate sound signal; that is why we first pass the signal through a divide-by-2 IC (IC2). You can use the signal from any of the outputs, depending on your personal preference (we used output ‘0’ (pin 9) – the input signal divided by two).
We use this signal to drive a very simple push-pull output stage (T1/T2), that nevertheless has enough power to drive a small loudspeaker.
The circuit is powered from 3 V (two AA-batteries); the current consumption amounts to about 13 mA maximum (0.66 mA when idle). R1 and C1 decouple the power supply voltage for the IR receiver to prevent any potential interference from the output stage.
Read more: FREE ELEKTOR CIRCUIT – ACOUSTIC IR REMOTE CONTROL TESTER