Nuts and Volts - December 2015

rotating R4 until LED1 just goes out and then back off R4 until LED1 comes back on. Remove the jumper from pins

1 and 2, and move it to pins 2 and 3 instead for normal operation.

If all has gone according to plan, you should now be able to walk your hallway without ever having to turn on another light again!

In Conclusion

Now that my hallway is automated, I plan on building additional modules to control other rooms in the house. The laundry room was built with the same problem — you have to walk across the room in the dark before you can turn on the light. In the bedroom — where I’d want the light to come on when I enter but turn off when I’m ready to go to sleep — I’ll add a SPST momentary pushbutton switch between pin 2 of IC2 and ground. Then, when I’m ready to turn in for the night, I just push the button and … lights out! In the master bathroom, there’s a double-door that stays closed (due to el gato). There, I will replace the IR detector with a magnetic reed switch pair, increase the delay time constant for IC2, and do away with IC1 and its related components. As you can see, the base circuit is quite versatile.

Don’t think that lights are all you can control with this! The relay I used (scrounged from an old CRT TV chassis) can switch loads up to 10 amps at 250 VAC or 24 VDC. Depending on the exact relay you select, your mileage may vary. Hopefully you found this interesting, or at least useful! NV