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Driving string of RGB LEDs over distance

M

Mike

Jan 1, 1970
0
Hi,

I need to drive 40 x RGB LEDs spaced at 25cm intervals over a distance
of 10mts.

Initial thoughts are to make a small PCB for each LED and use 3
Infineon BCR401R constant current LED drivers for each to ensure even
brightness along the cable run.

Hook-up wire for daisy chaining the PCBs will probably be solid AWG24.
Space is quite tight - the PCBs need to fit in a channel which is only
10mm wide.

The LEDs will be driven in PWM mode (for colour mixing) using a micro
and NPN bipolar/P channel FET switching the high side of 5, 9V or 12V.

Any suggestions or "gotchas" please?
 
B

Ban

Jan 1, 1970
0
Mike said:
Hi,

I need to drive 40 x RGB LEDs spaced at 25cm intervals over a distance
of 10mts.

Initial thoughts are to make a small PCB for each LED and use 3
Infineon BCR401R constant current LED drivers for each to ensure even
brightness along the cable run.

Hook-up wire for daisy chaining the PCBs will probably be solid AWG24.
Space is quite tight - the PCBs need to fit in a channel which is only
10mm wide.

The LEDs will be driven in PWM mode (for colour mixing) using a micro
and NPN bipolar/P channel FET switching the high side of 5, 9V or 12V.

Any suggestions or "gotchas" please?

I did some experiments with Kingbright 5mm RGB-Leds. It is not a good idea
to use drivers, because you need to adjust each LED to the same white colour
with all segments on. First use 2x47R for the 2 blue chips for a total of
50mA from 5V. then the green needs around 12mA, use ~120R and finally the
red needs less current, 9mA with ~330R. Adjust the resistors for each Led
individually, but keep the 50mA for the blue, as they are the weakest.
Best to do this with a duty cycle of 50%, to avoid overheating. compare the
color in a breadboard.
The resistors can be of the 100mW axial ones, use shrinktube to cover them
and make different lengths for each connection to avoid shorts. No PCB
needed, which will only break.
AWG 24 is to small, use it only for the gn and red and take AWG20 for gnd
and blue. Do not use higher current for the red or gn, since you will
overheat the chip and get the blue too weak.
 
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