How it works

The transmitter drives an infrared LED, and the receiver detects its signal and switches a relay. The restored page includes separate transmitter and receiver schematics.

To adjust the receiver, aim the transmitter at it while holding S1 and vary R6 until the relay responds reliably. Bright ambient light can reduce sensitivity or saturate the receiver.

Original schematic

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Figure 1 · NewCircuits archive · Download image ↓
Figure 2 · NewCircuits archive · Download image ↓

On the bench

Test with a low-voltage relay load. Confirm the relay coil drive and contact ratings independently. Any mains switching installation also requires appropriate isolation, clearances, fusing, and an enclosure.

Resources & provenance

Rewritten from the original circuits/sec/mn3qo9c_sec002.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.

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