Infra-red remote control - receiver

7-74 - elektor july/august 1982 After the transmitter using the SL 490, published elsewhere in this issue, we come to the receiver, once again using Plessey ICs, SL 480 and ML 920. Pulse pause modulation (PPM) is used with or without carrier, and automatic error detection is also incorporated. Although initially designed for TV remote control, the ICs can also be used for controlling "HI-FI" equipment, lighting, toys and models. Figure 1 shows the circuit diagram of the pulse amplifier. This mainly consists of three gain stages, each being decoupled by capacitors, so as to achieve low frequency roll-off, there- fore eliminating AF noise. The transistor capacitor network around T1 actively simulates induction, pre- venting the diode D1 from saturating. In other words, it gets over the problem of high ambient light, such as sunlight, from saturating the receiver diode. The photo diode D1 (which is buffered), sends negative going pulses to the input of the IC. This input is then am...