IKEA night light

Discussion in 'General Electronics Chat' started by ErnieM, Aug 21, 2011.

  1. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    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.
     
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    555 probably was used as a Schmitt trigger, I used that in a light triggered bike light. Nice find.
     
  3. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    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.
     
  4. Externet

    AAC Fanatic!

    Nov 29, 2005
    762
    57
    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.
     
  5. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    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.
     
  6. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    What was the zener voltage rating. Was this powering the NE555?
     
  7. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    I measured 6V on it.
     
  8. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Enough to run the NE555..!
     
  9. Externet

    AAC Fanatic!

    Nov 29, 2005
    762
    57
    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
     
  10. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    The article references the LMC555, a CMOS 555 timer IC, nothing new with that chip.
     
Loading...