Motion sensor to detect sneaking toddler

Once the kids are asleep at night, you can finally relax. Aahh. Maybe you want to stress down with a violent splatter movie with the volume at 11? In this situation you definitely do not want the kids to sneak around in the house behind you and watch the movie in secrecy. In that case you will have a lot of explanation to do. (Dad? What happened to the man's brain?). Or maybe you and your spouse are in your bedroom making new kids..? You definitely do not want the existing kids to interrupt such a beautiful moment. And difficult questions could possibly be asked.

The trick is to use a motion sensor outside the toddlers bedroom and a portable doorbell with visual and audible alarm. All possible crisis is henceforth avoided.

I bought one of these Nexa doorbells, and a...

... Nexa IR detector.

The problem with the doorbell is that is also chimes when someone are walking around in the house during daytime. It also chimes to loud for the intended purpose. Therefore, I added a volume control, that also serves the purpose as a on/off switch.

The doorbell is a simple design built around a 433MHz receiver

A 100k audio pot for the junk box does the job. I also tried with some resistors to limit the 100k pot with mixed success. It does not matter much for this purpose.

I drilled a hole in the front panel, and ...

Voila. A doorbell with a nice blue LED and fully adjustable volume with a Moog style knob. I glued some eyes to the doorbell to make it seem a bit more friendly.