LPD8806 RGB strip working without power

Hi all,

I have started playing with my new RGB led strip, and curiously enough, it lights up even without the +5V line connected. :o

I'm following this tutorial for wiring, and using the LPD8806 library from the same site.
I simplified the sample code to have just a single running light, and it works as it should in SPI mode. In non-SPI mode (with pin 2 and 3 for data and clock, respectively) the behavior is erratic. Not completely random, but not the expected either.

But what puzzles me the most is that all this happens with only three wires of the strip being connected: data in, clock in, and ground. No power.

How is it working at?

The strip must be be getting it's power from the data and/or clock lines. Many chips will do this when some pins are at a higher voltage than the Vcc pin. It is not a good thing and could damage the Arduino or the strip. Don't do it.

Certain chips are designed to work like this, for example ds18b20 temp sensors, in "parasitic power mode".

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