IKEA night light

Thread Starter

ErnieM

Joined Apr 24, 2011
8,006
I just pulled apart an IKEA night light to see how they are doing what they do. I don't think it is sold any more.

If you follow the link it's a little cylinder with a rotating dome, two blades in the back plug right into a wall socket. There is a light sensor window, when it's dark the LED comes on. I had to pull one apart to see how they ran a LED off the AC line. It's a pretty conventional capacitive divider driving a zener, and I wouldn't discuss those details here.

What I found interesting was the sensor/LED driver: they use what looks like a CDS photo resistor driving a... 555! Looks like they just make a resistor divider to the threshold input, drive the LED from the output pin 3 thru a resistor.

Thought it was fun to find a 555 inside there.
 

Markd77

Joined Sep 7, 2009
2,806
It's odd not to find a micro or custom chip in anything these days. I found this in an old camera remote control. The output is simple, but there are only about 18 of these pulses, no matter how long the button is pressed (it might be an exact number each time). Not bad for a quad NAND gate.
 

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Externet

Joined Nov 29, 2005
1,412
What you call "555" is NOT a NE555 timer.
There is another chip with three fives in the numbering. That is the one the night lamp has in it. You can post the correct complete number or search its data sheet.
 

Thread Starter

ErnieM

Joined Apr 24, 2011
8,006
What you call "555" is NOT a NE555 timer.
There is another chip with three fives in the numbering. That is the one the night lamp has in it. You can post the correct complete number or search its data sheet.
While there are lots of parts with 555 in the number, what I call a "555" IS an NE555.

The complete part number is "NE555." That kinda nails it. The schematic is compatible with a generic 555 type, so even if this isn't a classic 555 inside there you could put a classic 555 there and it would still work.
 

iONic

Joined Nov 16, 2007
1,650
Thanks, Ernie.

Been trying to find among my documents the other '555' used in that application, unsuccessfully yet, but I know I have it. Will post in the future whenever I find it.

Only found the page torn from a magazine (the way I keep articles of my interest filed) and references the net to a way a CMOS 555 does it. Enjoy :

----> http://power.elecdesign.com/Articles/index.cfm?ArticleID=22214&stylename=blue
The article references the LMC555, a CMOS 555 timer IC, nothing new with that chip.
 
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