My version two charlieplexed lighthouse circuit PCBs (charliediscs) have arrived back from the Seeedstudio’s fab. I used the same deal as for my last boards, this time it took around 3 weeks in total. That’s pretty good for 20USD!
I thought I’d have a go at getting my PWM controller PCB made professionally.
I had an email from a friend who has built my lighthouse circuit but whose LEDs were lighting up in the wrong order. This is exactly what happened to me when I built it the first time too. But no worries!
The great thing about charlieplexing and this circuit is that it doesn’t matter which order you place the leds on your board as you can change the code to match the correct sequence for your final layout. This means that you can layout your circuit for ease of wiring rather than having to keep the LEDs in any particular order. As long as the circuit is correct and that you have an LED everywhere you should have one the ordering can be sorted out later.
After about a day of messing about I finally managed to program the damned thing using ICSP rather than pulling the PIC each time.
Schematics lie! Especially when you draw them yourself. Guess what. Pin 5 of the PIC12f683 isn’t the ICSP clock line… Pin 6 is! Ah! Well there’s a lesson learned the hard way. Next time I’ll be more diligent when drafting things out in Eagle.
Here’s a quick video of the thing in action. It’s a bit fast for a lighthouse, more like a beacon. I’ll slow it down and maybe add a potentiometer to allow speed changes later on. I deliberately chose the input pin to be GPIO 4 as it’s one of the IO pins that is multiplexed with the analog to digital converter.
Apologies for the manky looking video, it’s hard to get
the camera to work well in low light conditions.
UPDATE Aug 7th 09 : You can get the Eagle CAD files here.
UPDATE Oct 2nd 08 : You can grab the source code and circuit diagram for this project from this blog post.
I’ve been working on a variant of the circuit I developed for my Lego beacon. It’s the same basic circuit but this time with 12 rather than 8 LEDs and rebuilt into a circular 40mm dia (1.5 inch) double sided disc.
The idea is to use this as a simple “lighthouse” that when powered up will rotate the beam around the 12 LEDs. I’m not sure why I’m building it, I have no real need of a lighthouse… Maybe it could be useful for a model railway or something similar. But I kind of like the idea of it and had some neat OSRAM SIDELEDs in my parts box that were calling out for some use.