Making a Night Light from an IKEA LED Lamp

After a request for some night lights I remembered that I had some IKEA motion sensitive LED lamps that were bought for use in cupboards. One is still in use, the other (they come in packs of 2) was just lying about. They are easy to fix to walls and battery powered, so no trailing cables. I tried one as a night light months ago, but it was very bright and came on during the day as well, so it was removed from duty.

Thinking about the new request, I wondered if the lamp could be modified to add a 'darkness only' feature. Dismantling the lamp revealed a standard PIR chip inside: the BISS0001. Looking at the datasheet revealed even more good news: the chip has a function that  disabled the output from triggering if it detects light. The example circuit has the components for this feature included.

I ordered the parts (100k resistor and an LDR) after working out the values I needed.

I modified one lamp and it didn't work, this was due to the routing of tracks on the PCB, so I lifted the pin on the IC and added the components directly to the pin. SOIC chips don't have robust pins, so bending it up once is about all it can manage. Any more flexing and the pin falls off.

After adding the components correctly, the lamp now only triggers and turns the LEDs on when it is dark. I've also removed three of the four series resistors that current limit the LEDs, as the amount of light given off was too much for a night light.

You also have the option of changing the time that the lamp stays on for, by changing the value of a resistor (or capacitor). This is detailed in the datasheet.

Lift the pin 9 leg:

Then put a 100k resistor from pin 9 to pin 11:

The LDR (light dependent resistor) looks like this:

I used my CNC router to cut a hole that matched the shape of the LDR and glued it in place:

The legs from the LDR wrap around the PCB quite nicely:

One leg can be soldered to the track at the edge of the PCB, the other requires a wire to run to pin 9:

I have modified one of the lamps to have a longer ON time, the rest are as they came. They've been running for a while now and are pretty useful.

These are the LDRs I used:
https://www.ebay.co.uk/itm/192823191519
The resistor was a standard 1206 100k surface mount resistor.

Not My Hack

In the UK we have string pullcords on lights in bathrooms. These are usually in two pieces, joined with a plastic or metal widget that has a couple of holes, one in each end.  You put the ends of the two piece of cord in the holes and tie two knots to hold them there. then you hang a quirky thing off the end of the bottom cord. the plastic 'joiner' in a friend's house had broken, and he wondered if I could make a replacement. I thought about it for a while and made this:

Before  I had a chance to deliver the part, I was sent this photo of his solution:

This was just too good not to put up here. It's cheap and effective, and has the quirkiness required of a pull-cord. How long will it last? Who knows? But then, it doesn't matter, as you just replace it with another bottle...