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Author Topic: PWM rgb ledstrip  (Read 1833 times)
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Hello,

I'm having some issues with PWM-ing a rgb ledstrip.

I've bought the following ledstrip: http://www.ladyada.net/products/rgbledstrip/ (3 meters/30 leds p/m => 90 rgb leds => 270 leds)

I'd like to make my own RGB-led controller using RF to turn it on/off/change colors. This means I have to use VirtualWire. This takes up my timer1. So I only have 4 pwm pins left. I've tried some combinations, but somehow this always results in flickering leds when I turn them down to ~25%.

I've thought of buying the tlc5940. But if I'm correct, the library for the tlc5940 uses timer1 and timer2. So I can't use virtualwire in combination with tlc5940?
Now I've ordered https://www.sparkfun.com/products/10444, but I'm not sure if this will solve my issue.

Can someone enlighten me on what my problem is here? Is it because I use 2 different timers to PWM the ledstrip? Or is it possibly the powersupply? Will the WS2801 solve my issue?
« Last Edit: September 26, 2012, 03:34:10 am by Cypher87 » Logged

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If the strips are continuous you only need one PWM output pin per color.  If things start to flicker noticeably I would suspect the power.  At 600 mA/m and 3 meters of lights you need a 1.8A (or higher) 9V to 12V power supply.  What is the power rating on your power supply?
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Yes it is continuous. I've bought a 12v/5A power supply. This should be plenty right? If I turn the leds to 100% (analogWrite(x, 255)), the strip is not flickering. Only if I turn it down to ~25% it's very noticeable. Could this still be a power related issue?
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Do you have power transistors for each color?

Flickering almost certainly leads to dirty power/ground issues.
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I'd like to make my own RGB-led controller using RF to turn it on/off/change colors. This means I have to use VirtualWire.

How so?  I built several RF controlled modules last year with RGB LED strings.  My setup consisted of two strings containing 20 RGB LEDs each, driven by WS2801s (one per RGB LED).  I used bit banging to control the strips.  I used an nRF24L01+ RF module which uses SPI to communicate with the µC.  Didn't use VirtualWire.

One module acted as a master, sending RF signals to the others, telling them how to change.
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Do you have power transistors for each color?

Flickering almost certainly leads to dirty power/ground issues.

Yes I do have power transistors. If it would be a dirty power/ground issue, shouldn't it be flickering disregarding the pwm duty cycle?

How so?  I built several RF controlled modules last year with RGB LED strings.  My setup consisted of two strings containing 20 RGB LEDs each, driven by WS2801s (one per RGB LED).  I used bit banging to control the strips.  I used an nRF24L01+ RF module which uses SPI to communicate with the µC.  Didn't use VirtualWire.

One module acted as a master, sending RF signals to the others, telling them how to change.
Even so, the flickering shouldn't occur anyway rights? Using pins 3,5 and 6?
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Even so, the flickering shouldn't occur anyway rights? Using pins 3,5 and 6?

Well, I'm sure your circuit isn't the same as mine.  I did not have flickering issues with PWM controlled brightness on LEDs, so yeah, I'd say something's up.  Can you post a schematic of how you have things wired up, what components and such?  Perhaps collectively we can figure out what's going on ...
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This is basically what my schema looks like:



This is (of course) without the RF receiver. Which has a gnd, 5v and a data pin.

The npn I took of a rgb controller like this one:



Two of them say: d3002, 0604, MO235F
The other one says: mdd1653
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Only suggestion I can think of is to try powering the LEDs with a separate 12v power source.  I'm wondering if the operation of the arduino if causing the VIN voltage to waiver on you.
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