hi i would like to add some lovely 365mn 3w uv leds i have to a pixelblaze installation. i need about 20 of them. i assume that small drivers with some SPI interface must be available, but im having trouble locating something that is not either a bare IC or a box which can drive hundreds+ leds. Since these leds will be spaced several metres apart this adds a further complication with signal integrity. any advice?
Something like our ws2811 breakouts can be used to generate the PWM signals, but you’d need some driver circuitry to efficiently feed the 3w LEDs. You could do that with a beefy PNP transistor and some power resistors, and while simple, it wouldn’t be super efficient and would generate more heat. For higher power LEDs, usually there’s a constant current buck converter (or three) involved, and you’d need one that accepts a PWM input. More complex but efficient.
There are existing addressable 3w modules for RGB that use a ws2811 and have extra driver circuitry, you might mod something like that and replace the RGB led with your UV LEDs. I’ve seen a bunch on Tindie.
The ws2811 signal is good for 10-20ft. There are ways to extend that further if needed.
ahaha as usual every time i ask here a solution is readily available. nice! i didnt know about the breakouts. well i guess i could wire 3 constant current drivers with pwm input to your ws2811 breakout, and then run the 5-7m cable runs from there to 3 of the leds. i guess the cc driver would compensate for any cable resistance… i assume that would be preferable to dealing with long runs from pixelblaze to the breakout. the only thing i dont understand looking at, for example, these:
is the description states " current control via potentiometer or pwm - as in two distinct modes… the description seems similar on all of the similar models ive seen.
i hope the potentiometer is used to set the max current and the pwm varies between that and lower outputs. if using pwm overrides the potentiometer how would i set the peak allowable current? id hate to blow one of my few leds they were not cheap …
I’d put the electronics closer to the LEDs. Should be ok with 5-7meters. Can always put an empty ws2811 breakout in between to regenerate the signal ( though you have to account for the extra ghost pixel)
Yeah I imagine the lot sets the constant current aspect, and PWM goes on top of that. If you don’t want to risk it, throw a high power resistor in there instead of your led, then monitor the voltage to figure out how much current it’s getting. That would be a safe way to adjust the pot too.
ok thank you so much for your suggestions. most appreciated.