This instructable is another simple make but yet practical as I think, my daughter has a bad habit not turning off the toilet light after used, so I try PIR if can be solved. I think this could be simple and need not Arduino to program about, of course I got the PIR aimed to play with the Arduino.
Step 1: PIR HC-SR501
The PIR model I used is HC-SR501, you may find alot of this in other instructables, some adjustment made only on the right jumper to move down position as shown, and adjust the turn off time on the left potentialmeter, normally right turn to increase.
Step 2: AC Solid State Relay
To control AC light, I used a solid state relay model Z240D10, the schematic as shown, the AC load is simply in series. Of course you may not having this, if you would follow you can use a non solid state relay with transistor driver as shown, the major caution is the power of loading point in the relay as you are connecting AC. The PIR and/or relay circuit needs 5V power, you may consider using a scraped mobile phone charger.
Step 3: Packing It Up
My toilet is also serve as the bath room, so I pack it up in a plastic box to prevent moisture and hang it under the ceiling in the central of the room, the rather hard job is to climb up the ceiling to change the wiring. After installed, the light switch still can be used normally, but if light is not turn off and walk away, it will auto turn off after 15 minutes, I guess so, you can always adjusted the length, or if you felt asleep inside, the light will also turn off, don't panic, just wave the hand or your head to get it back.