Passing through the Ikea Marketplace the other day I was tempted into buying a pack of two battery-powered, motion-activated LED lights, intended for installation inside a wardrobe. £4.99 for the pair. I thought they'd make a good night-light for nocturnal trips to the loo.
What I hadn't realised is that they activate regardless of whether it is light or dark, so if I put one of these in the bathroom it'll be coming on during the daytime as well, which will run the batteries down a lot quicker.
I opened one up to see what was inside. I found a datasheet for the BISS0001 chip that powers it, and this revealed that it has a "Trigger disable input" pin, which was tied high with a 1M resistor.
One light-dependent resistor salvaged from an old night-light, a bit of dremelling and soldering, and the light now only activates when it's dark. The LDR pokes through a small new hole on the front:
and is connected between pin 9 of the IC and ground: