Cheap RGB LED Strip (non-addressable)

Other Hardware LEDs and Multiplexing
1

Has anyone used the RGB strips like these - http://amzn.to/15h07J3 at £17 / 5m? It seems incredibly cheap compared to the ones from mainstream dealers. e.g. the seemingly equivalent from protopic is £15 / 0.5m.

I don't quite understand why they can only be cut every 3 LEDs though, and why it says they only support 16 colours, so there must be more to it than simply RGB and ground.

I'd like to try some but wondered if anyone had any experience of them? There's hundreds similar on ebay etc.

thanks!
Mark

EDIT: I think the 16 color thing might be referring to the control box, which is extra. If anyone has used these and has any advice I'd love to hear it!

2

markvr:
Has anyone used the RGB strips like these - Amazon.com. Spend less. Smile more. at £17 / 5m? It seems incredibly cheap compared to the ones from mainstream dealers. e.g. the seemingly equivalent from protopic is £15 / 0.5m.

There's big differences between those and the ones with built-in controller chips...

markvr:
I don't quite understand why they can only be cut every 3 LEDs though

They run at 12V.

12V can power three LEDs in series so they're wired as parallel strings with three LEDs in each string.

markvr:
and why it says they only support 16 colours, so there must be more to it than simply RGB and ground.

That's just the matching controller. If you're PWMing it yourself you can do full color.

3

fungus:

markvr:
Has anyone used the RGB strips like these - Amazon.com. Spend less. Smile more. at £17 / 5m? It seems incredibly cheap compared to the ones from mainstream dealers. e.g. the seemingly equivalent from protopic is £15 / 0.5m.

There's big differences between those and the ones with built-in controller chips...

The ones I was comparing to were these - http://proto-pic.co.uk/rgb-flexible-led-strip-30-way-0-5m-length/

markvr:
I don't quite understand why they can only be cut every 3 LEDs though

They run at 12V.

12V can power three LEDs in series so they're wired as parallel strings with three LEDs in each string.

Ah, cool that makes sense.

markvr:
and why it says they only support 16 colours, so there must be more to it than simply RGB and ground.

That's just the matching controller. If you're PWMing it yourself you can do full color.

Excellent thankyou, these look perfect then for doing colour washes. I also found someone who has done something similar - http://ikennd.ac/pictures/ArduinoDioderWiring.pdf

Does that circuit look OK, or would I need constant current drivers or similar?

4

markvr:
The ones I was comparing to were these - http://proto-pic.co.uk/rgb-flexible-led-strip-30-way-0-5m-length/

Those are much too expensive. Not a good comparison.

I was comparing with these: http://www.ebay.com/itm/160907739909 where each individual LED has a built-in PWM controller.

markvr:
Does that circuit look OK, or would I need constant current drivers or similar?

They should have built-in resistors to work at 12V, no current driver needed.

5

Does that circuit look OK, or would I need constant current drivers or similar?

Yes the circuit looks OK note that each UNL2003 can only drive about 650mA in total due to thermal considerations.
See:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html
So you might want to use one UNL2003 for each of the colours. You can parallel up the inputs and outputs of each single device and if you feed them from PWM capable pins you will have good control over the colour.

6

Cool thanks for the advice both. Am making a Tron Legacy costume, but with a twist that I want the strip colours to be sound reactive.

7

That circuit looks cool but I'd rather use three MOSFET to drive these LED strips -- they are constant voltage type of strip, so it is much easier to drive.