Friday, 17 February 2012

Ikea wardrobe light hacking

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:

Now the only problem is that it's much too bright.


Anonymous said...

This is a cool gadget to hack. Thanks for linking to the AppNote... :)

Sverre Holm said...

Your post demonstrated that these lights are simple to open and modify, thus helping inspire another modification: "Simple IKEA transmit indicator"

Anonymous said...

Hi Rob,

Nice hack!
What resistance range is the LDR?


Anonymous said...

Thanks for sharing this hack.

I am going to give it a try too.

Did you solder the LDR between pin 7 (Vss Ground) and pin 9?


Rob Noble said...

Oops, sorry for the slow replies:

GR JC - I'm afraid I don't know the resistance range of the LDR - it was salvaged from a nightlight, and I didn't test its range - sorry.

Gary - You can see where I soldered the LDR in the last picture - the black wires at the bottom left are from the LDR. The pins on the IC are too small to solder wires to, so I followed the traces and found larger places to solder to - the battery connection in one corner (v-) and one end of resistor R4.

Jeroen Kransen said...

Thanks for sharing! I also played with the idea of reverse engineering and hacking this device. I use one for the same purpose as you, and ran into the same restriction. It would also be fun to use the motion detection function separately on e.g. an Arduino. Do you know if that can be done easily, like a pin on the IC that goes high when motion is detected? The sensor itself does not seem to be easy to read by itself.

Jeroen Kransen said...

Pin 12, "2 Out" looks like a good candidate to connect to the outside world. It remains 0V without motion and turns to +3V when motion is detected. Time to tie that pin to my Raspberry Pi :-)

Rob Noble said...

Hi Jeroen,

Based on the application example at the end of the datasheet I'd say that pin 2 (detector output pin, active high) is the one you want.


Kacitran said...

This is the data sheet. here you have all the information you need.

shortly display information in my blog.

Theo van Wessel said...

Super post, thanks!

About the bright light: you can disconnect two of the four LED's or put a small resistor in line.
When you use the lights for inhouse night orrientation you can change the LED's into amber coloured LED's.
The human eye responds best/most softly to amber colour when walking in the dark and don't want to wake up by too much light.

Theo van Wessel said...

By the way: did some one or Rob your self maneged to determine the appropriate LDR and resistor value for this hack?

Rob Noble said...

I didn't, sorry. Perhaps a starting point would be to fit a variable resistor and adjust it to the desired switchover point, then measure. Then somehow work out what LDR value that translates to.

Theo van Wessel said...

Hi Rob,

The variable resistor would be an option, only then you need to have the min-max range.

I found on the internet that a LDR for general purpose has a resistance of about 1-10M by dark, and about 75-300Ohm by light.
Maybe choose a 10M var resistor then...

A local store has a lot of LDR's in different ranges. Most are 100K at 0 Lux, some 2000K.

It would be possible for you to do a fast test with your multimeter and help us out with the LDR values in light and dark situation?
(Only when you can and have time, otherwise I will do the var resistor test.)

Theo van Wessel said...

Just took a regulair LDR out of a twilight switch and it worked well.
Also I did not had the capabilities to meassure the value.
Most probably all average/most used LDR's will work.

Anyway, Rob I want to thank you for sharing your knowledge.

And by the way, this IKEA light was a one time product.
When they are out of stock, they will not return in shop.

Anonymous said...

Thanks for the hack!
Regarding brightness, you could maybe disabled 1~3 pf the LEDs?

Now I'd like to reduce that 30" duration...