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?
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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.