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We bought some Serial LED strips for the shop and I am having a whole lot of fun programing them. Like most 12 volt strips they are wired with three LEDs in series, which are in turn controlled by one high-speed serial chip. So there are 50 control chips on a 5 meter strip. (The strips have 30 LEDs per meter). We looked for strips with 60 LEDs per meter but our supplier could not provide them without a sizable order from the factory.
The somewhat coarse grain of this control might be a show-stopper for some LED projects, but they’re well positioned for lots of general computer-controlled changeable color and display applications. I am having a whole lot of fun programming them. I found an excellent high-speed library here. The author hasn’t returned my email yet, I’ll call him Daniel G. from his email address, and give him more specific credit if I can get in touch, and he wants the attention.
Our LED strips are controlled with the UCS1903 chipset, which has, as one of its great virtues, the ability to control the LEDs with only a ground and data line. All of the Chip Select and Clock functions have been replaced in the chip, by careful timing control, which also requires a microController running at least 16 Mhz, so Lillypad owners are out of the picture, at least for now. The lack of clock signal lines creates a very clean interface. Two wires, Ground and +12 volts, go to the strips from the power supply, and two wires, GND and Data In, connect the microcontroller to the strips. The strip headers thoughtfully have two wires on ground (if you buy a whole 5 meter roll), so it’s a very easy hoookup. More strips can just have data and GND lines daisy chained, and power lines perhaps run in parallel, to avoid huge currents through the strips, although it might be possible to run 10 meters daisy chaining all four wires, especially if all the LEDs are not on at any one time.
Writing 255, 255, 255 to all LEDs yields a strip (5 meter) operating current of 2.3A (@ 12 volts). The total current divided by 150 (50 controller chips x 3 colors) yields about 15mA per LED so the strips should have a long lifetime at that current, since most superbright LEDs are usually rated at 20 mA or greater.
I cooked up five demo sketches to help users get going on using the library. There are some videos below (of uneven quality) showing the effects. There are some nasty flickers in some of them that just represent interference patterns between the video frequency and the update frequency of the LED’s. Needless to say, the LEDs don’t look like this to the human eye. Cyborgs though, will eventually be connoisseurs of visual phenomenon entirely invisible to people.
The Serial LED strips are in stock and in the shop here.
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