[Lab] christmas light pcb

Peter Sjoberg peters-modlab at techwiz.ca
Mon Dec 24 11:41:01 EST 2012

On Mon, 2012-12-24 at 06:46 -0800, Richard Wiens wrote:
> Peter,
> If you go to the Adafruit website and look at their material on
> addressable LED strips you should get some clues.  You basically use
> PWM to control each LED...the kind of chip will dictate whether you
> need to keep sending the signal or just send it once and the chip will
> keep PWMing until you change something.

The first chip has _only_ power and out from that is 3 wires, gnd,data,
+5. Don't know if it can be parasiting to much from the power since it
goes directly from the 7805 to all the cards. 
They do not blink randomly, all/sections come on blue/green/white,
change color in sequence, chasing light and so on, so it's some
intelligence there, and with only one wire it must be one way only or
some single wire protocol. Come to think of it I don't think it ever
changes backwards, I think changes always goes from the power side to
the end. Don't know if it need to be PWM since it looks more like on/off
then dimming so it may only need 3 outputs but once it get the signal of
what to turn on it can probably keep that on until new orders come.

The adfruit ones (306(HL1606) & 322(WS2801)) have 4 wires so the
protocol can't be the same. 
Now thinking about it, since this lights starts at power on and it's no
separate controller box (was expecting the small box in the beginning to
have some smarts but it was just a rectifier, 7805 and a cap) they must
be custom chip or programmable (PIC).
What I was hoping was to be able to control the lights individually to
make some light painting or so. After christmas I will take a scope and
see what the data line looks like and also try to hook it up to read the
bits (what's the safest way to read 5V with raspberry pi's 3.3V
unbuffered input short of buying some chip?) but don't expect much

> Richard
> From: Peter Sjoberg <peters-modlab at techwiz.ca>
> To: lab at artengine.ca 
> Sent: Monday, December 24, 2012 3:17:55 AM
> Subject: [Lab] christmas light pcb
> I picked up a Christmas light at walmart and trying to find info about
> it. What interested me is that for $8 I got 15 RGB LEDs, each with
> it's own little pcb and it seems like they can be controlled
> individually! Of course it's not as simple as reading the specs
> because I haven't found any (did google the numbers found) and the IC
> is a black blob so no help there.
> I opened up the first and last one to take some pictures. The first
> one has 5V feed on the upper row marked "DI", the bottom row marked
> "DO" has 3 wires going to next light where it comes in on the "DI"
> row, out on a "DO" and my guess is that it goes on like that to the
> end.
> I took some pictures of it that can be seen at
> http://flickr.com/gp/henahadu/73436S/ 
> My question is - anyone seen anything like it ? Any clue on where/how
> I can find more info? Somewhere else to ask ?
> /ps
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