Hi there, I'm just starting a little project involving a PIC, some LEDs and a bit of PWM cleverness. Basically, I want to modify the Poi I built to add more colours + flashing and strobing effects. Here's a shot of them as they are at the moment :
**broken link removed**
I've posted some stuff about this on other forums, but not really got anywhere. I'm very new to PICs, but I've done a little assembly and a LOT of C/C++/VC++ coding before. Basically, I want to run 3 PWM channels to flash red, green and blue LEDs to reproduce a large range of colours. I also want to make strobing effects and colour changes and a load of other effects. Here's a few :
**broken link removed**
...now come the problems :
1) I want to run all this off 4xAAA batteries, and if it's possible, avoid using resistors to drop the voltage down. Afterall, PWM is supposed to make things more efficient isn't it?
2) I'm not 100% sure, but I think I need my PWM signal running at ~100KHz. Poi are swung around fairly fast, so too slow and the colours will seperate and you'll see the strobes seprate which is an undesirable effect. I took a vid of myself doing some Poi using my digicam earlier. It takes movies @ 15fps. Now knowing that and the length of the chains, we should be able to calculate how fast the things move and therefore, the minimum speed we need to do the PWM so you can't see it.
Here's what I've got :
Chain length : ~0.8 m (that's from the handle to the tip of the LED tube)
Frame Rate : 15 fps
Angle covered between frames : ~45°
Circumference of the circle the Poi spin through = 2*Pi*r = 5.03 m
Distance travelled by the Poi between frames = circumference * angle / 360 = 0.63 m
Approximate speed of Poi = distance / time = 0.63 / (1/15) = 9 m/s
So what kind of seperation will there be between flashes?
100Hz => 94.2 mm
1KHz => 9.42mm
10KHz => 0.94mm
100Khz => 0.094mm
Okay, that's enough for one post.. So what PIC would you recommend to run off a 5v supply to produce 3 PWM signals at the kind of speeds I'm after? Let me know what you think! All comments / suggestions are most welcome!
**broken link removed**
I've posted some stuff about this on other forums, but not really got anywhere. I'm very new to PICs, but I've done a little assembly and a LOT of C/C++/VC++ coding before. Basically, I want to run 3 PWM channels to flash red, green and blue LEDs to reproduce a large range of colours. I also want to make strobing effects and colour changes and a load of other effects. Here's a few :
**broken link removed**
...now come the problems :
1) I want to run all this off 4xAAA batteries, and if it's possible, avoid using resistors to drop the voltage down. Afterall, PWM is supposed to make things more efficient isn't it?
2) I'm not 100% sure, but I think I need my PWM signal running at ~100KHz. Poi are swung around fairly fast, so too slow and the colours will seperate and you'll see the strobes seprate which is an undesirable effect. I took a vid of myself doing some Poi using my digicam earlier. It takes movies @ 15fps. Now knowing that and the length of the chains, we should be able to calculate how fast the things move and therefore, the minimum speed we need to do the PWM so you can't see it.
Here's what I've got :
Chain length : ~0.8 m (that's from the handle to the tip of the LED tube)
Frame Rate : 15 fps
Angle covered between frames : ~45°
Circumference of the circle the Poi spin through = 2*Pi*r = 5.03 m
Distance travelled by the Poi between frames = circumference * angle / 360 = 0.63 m
Approximate speed of Poi = distance / time = 0.63 / (1/15) = 9 m/s
So what kind of seperation will there be between flashes?
100Hz => 94.2 mm
1KHz => 9.42mm
10KHz => 0.94mm
100Khz => 0.094mm
Okay, that's enough for one post.. So what PIC would you recommend to run off a 5v supply to produce 3 PWM signals at the kind of speeds I'm after? Let me know what you think! All comments / suggestions are most welcome!