LED project help

Using Arduino LEDs and Multiplexing
1

I am trying to do a LED installation that is not working.

I have two color faders, each powered by its own 300W power supply and arduino. From the power supply and Arduino each color is connected by about 20 feet of 12AWG stranded cable and Cat5 for the pwm to power 45 feet of RGB LED strip. This is happening twice, i.e., I am running this cable from the power supplies and arduino in the center of the room to each side. Each color on each side is using IRF510 MOSFETs to drive the common anode LEDs.

When I run just one color to both sides, or when I run two colors to one side, everything is fine. But when I run two colors to two sides the LEDs flicker erratically and are overall dimmer. Does anyone have ideas? I would be surprised if it was a problem with voltage drop since I have two power supplies.

Thanks for any help.

2

I am trying to do a LED installation that is not working.

Looks like you have succeeded. You are trying to make something that does not work and it doesn't, well done.

Your problem is supply decoupling or rather lack of it.

3

"Looks like you have succeeded. You are trying to make something that does not work and it doesn't, well done."
Yes, well I'm good at my job.

Thanks for the idea, I didn't even think of caps. Nearer to the MOSFETs I assume, right? Any guesses on the value?

4

Any guesses on the value?

I would guess a 0.1uF ceramic for the high frequencies in parallel with a 100 to 470uF for the low.

Nearer to the MOSFETs I assume

Across the supply close to the LEDs

5

The 20feet of CAT5 cable for the PWM would worry me a bit was well. I would expect some signal degradation particularly if the PWM is running at higher fequencies.

6

Well it is not only that but that amount of cabling will radiate like **** with PWM so the project might not even be feasible.

7

Thanks everyone for the help—the caps totally fixed the problem. The installation is complete and working, but just for future reference, what would y'all recommend for PWM cabling instead of CAT5? Any other suggestions for running long stretches of power and PWM data for a similar project?

8

I imagine you will have better results with coaxial cables with good shielding. cat5 cables have crappy shielding, it mostly relies on twisted pairs.

9

cshannon:
for future reference, what would y'all recommend for PWM cabling instead of CAT5?

Shielded cable like coax tends to have a high capacitance that degrades the signal. Flat ribbon cable is perhaps the best with one wire signal with a ground carrying wire on either side.

Any other suggestions for running long stretches of power and PWM data for a similar project?

Try and avoid it if you can with the design of your system.