One last plug… who knows, with a bit of luck, some of them might just work on first try?
The Dimmer Plug controls up to 16 LEDs or other lamps, and is based on the PCA9635 chip:
It’s driven from the I2C bus, with a couple of jumpers to allow daisy-chaining up to 8 plugs on a single port:
Here’s an extract of the datasheet, showing the different ways to hook up LEDs:
Basically, you can drive one LED directly per pin, or add a transistor to drive many more in parallel or in series. The chip just does the PWM part, with various blinking options and more, all from an I2C bus.
To drive high-power displays, the outputs can be tied to darlington arrays such as the ULN2803, or to MOSFETs. There are no drivers on the plug because there are too many different usage scenarios. It all depends!
Originally, I wanted to make this plug also fit on a the back of a display such as this one:
That pressure plug on the photo was added for size comparison. It’s the same size as this Dimmer Plug, which happens to allow daisy-chaining two such displays tightly next to each other when you include the headers.
But I can’t make it fit without widening the plug and mounting components on both sides. So I’ll leave it as is – it could still be mounted on the back by adding lots of little wires and 16 resistors, but it will take some more work. Or one could add a little board to sit in between, with 16 resistors and pins to stick into the 3×6 headers.
Now I’ll stop with this plug madness. Need to finalize all the layouts and traces, send the designs off, and then the waiting starts. Luckily, there’s still enough other stuff left to do around here :)
Update – there are some errors in the schematic. I’ll fix them before sending off this board.