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[on:]

Hi Everyone
I am new to Arduino and I have an led project i'd like to attempt. I have 5 x 1m strips of led's operating on a 12vdc supply. I need to have them switch on sequentially, but with fading. When triggered, strip 1 needs to fade in to maximum brightness, stay on for 2 minutes and fade out. Strip 2 will then fade in and do the same for the rest until strip 5 fades out. Sequence would then start again. I have fairly good electronic knowledge but not on arduino. Please advise as to what I require to get me started. Thanks Guys.

[Reply #1 on:]

Hi Everyone
I am new to Arduino and I have an led project i'd like to attempt. I have 5 x 1m strips of led's operating on a 12vdc supply. I need to have them switch on sequentially, but with fading. When triggered, strip 1 needs to fade in to maximum brightness, stay on for 2 minutes and fade out. Strip 2 will then fade in and do the same for the rest until strip 5 fades out. Sequence would then start again. I have fairly good electronic knowledge but not on arduino. Please advise as to what I require to get me started. Thanks Guys.

I'm assuming you are using static strips. Meaning, The four wires are 12V DC, Red, Blue, and Green. (not in that order, possibly). For these types of strips, what you want to do is impossible, unless you connect each strip to it's own ports in the arduino (All can use 12 V). However, if you want them to fade, each wire would have to be connected into a PWM Port. I know for the arduino, there is only 6 of these (So only 2 total strips could fade). So for 3 colors * 5 strips, you'd need 15 PWM ports.

You may be able to do it with a latch and such. But pure Arduino, it's impossible.

**Note: I'm also assuming you're using RGB LED strips.**

[Reply #2 on:]

Apologies for not giving more info on the led strips. I am using the single colour white led strips, so they will only have 2 wires 12v+ and neg. Is it possible with these? Thanks

[Reply #3 on:]

Apologies for not giving more info on the led strips. I am using the single colour white led strips, so they will only have 2 wires 12v+ and neg. Is it possible with these? Thanks

Anything is possible in the world of Electronics. Yes, it is possible with these.

As i said earlier though, each strip (so 5 strips) will need to be PWM-ed. Since there is only one color, you will only need 5 PWM ports, so an Uno, for example, will work perfectly!!

Instead of trying to explain, this example from Adafruit is what I am using doing this project. Granted, it uses a RGB strip, but it should be the same thing (and according to their site it is!):

http://learn.adafruit.com/rgb-led-strips/usage

Hope this helps!!

[Reply #4 on:]

Thanks Alot !!! I will attemp the project and let you guys know how it turned out.

[Reply #5 on:]

I believe it is possible even if you have RGB strips, just roll your own PWM code and 5x3 = 15 port on Arduino, of course, your CPU time will be tied up.

In my opinion, the PWM from Arduino causes flicker when dimmed closed to zero because the PWM frequency is NOT high enough. You can increase the PWM frequency on Arduino to avoid this. To do that, google it please, I am new to Arduino, too :-)

Regards

[Reply #6 on:]

The " standard" PWM frequency on the Arduno boards is 500 Hz. Frequencies over 100-120hz are not visible to most people.
It may have more to do with the 8- bit resolution of the Ardinos PWM signal in combination with the non linearity of the human brightness perception.

In my own projects trippylighting.com I use an Led driver board http://ledshield.wordpress.com/ with 12 bit resolution, allowing me a CIE brightness corrected dimming, alas at about 120Hz (IIRC) PWM frequency. Smooth as butter dimming without any perceivable flicker.

[Reply #7 on:]

The " standard" PWM frequency on the Arduno boards is 500 Hz. Frequencies over 100-120hz are not visible to most people.
It may have more to do with the 8- bit resolution of the Ardinos PWM signal in combination with the non linearity of the human brightness perception.

In my own projects trippylighting.com I use an Led driver board http://ledshield.wordpress.com/ with 12 bit resolution, allowing me a CIE brightness corrected dimming, alas at about 120Hz (IIRC) PWM frequency. Smooth as butter dimming without any perceivable flicker.

I did a RGB LED strip controller with IR remote, I coded my own three channel PWM with 8bit resolution, I did not see flickering even thought the MCU is a 8-pin PIC12F629 running at 4Mhz (1 MIPS, though as PIC divides clock by 4). With all the looping and conditions, I think I was running it at 20KHz (not very sure because of IR decoding logic was also in the code).

I think you are right about perception -- at low intensity, a bunch of lower intensity cycles are perceived together as dark, thus the enlongated "dark" cycle that appear as flicker.

Just a hunch.