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Topic: independant control on led chains. (Read 2687 times) previous topic - next topic

feltonn

Hello makers.
I need to create ribbons of white leds which could be independently driven.
I have read about addressable led strips but they are quite expensive for me and I don't need RGB colors.
I haven't found any "white-only" addressable strip.
Using shift registers does not really suits my project as I need real ribbons and no led grids.

Thus, I thought It may be possible to create little PCB  with a led and a chip ( like ones found on addressable strips) , that I could daisy chain?
I've just seen this video of an artist who seems to have build such little boards:
http://frey.co.nz/nowtheyknow
(The boards are shawn at 1'30" on the video.)

I'm a real beginner but with a great will to learn. So if you recognize the components used to build those boards, I would be glad to know more.
Thanks.

Grumpy_Mike

From the description it looks like they were not controlled at all, so the circuits they used would not be suitable for arduino control.
A shift register output dosn't have to be in a matrix, they can be arranged any way you want.

feltonn

Hello Mike.
I need a 5 meter long strip.
I thought It would be quite hard to arrange a matrix this way?

Grumpy_Mike

You keep using the word matrix, do you know what it means? It is where the anodes are connected together and the cathodes are connected together in a rectangular grid.
Using a shift register has one output per LED and they can be chained in strips.

feltonn

Sorry, I missread (sorry for my english by the way)
I'm a bit lost in the vocabulary used for multiplexing tasks. most of the "how to's" I saw was about matrices
Can shift registers be 1 meters distant from each other?

Grumpy_Mike

Quote
Can shift registers be 1 meters distant from each other?

Yes if you wire it up right and have good decoupling.

Quote
used for multiplexing tasks

Using a shift register is not multiplexing the LEDs, it is multiplexing the data line coming out of the arduino. Multiplexing an LED is when it turns on and off rapidly but looks like it is on all the time. With shift registers the LEDs are on all the time.

CrossRoads

So you are looking for something like a string of say 255 LEDs, where each LED has its own address, you would connect all with common power, ground, serial-input, each would listen for its address and then act accordingly? Could have each buffer the input and pass it along to maintain signal integrity.
5 meter, 195 inches/500cm, you could have an LED/board about every 2 cm.
Send 2 byte message - 1st is address, 2nd is data telling it what to do.
Maybe have a couple addresses that are global commands.

This kind of thing
http://www.bliptronics.com/item.aspx?ItemID=88
but with white only?

Maybe have each board have an LED, current limit resistor, 8-pin ATTiny85, and a single buffer chip.
http://www.ti.com/lit/ds/symlink/sn74lvc1g125.pdf
or make  your own with 2 NPN transistors (back to back inverters)
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

feltonn


So you are looking for something like a string of say 255 LEDs, where each LED has its own address, you would connect all with common power, ground, serial-input, each would listen for its address and then act accordingly? Could have each buffer the input and pass it along to maintain signal integrity.
5 meter, 195 inches/500cm, you could have an LED/board about every 2 cm.
Send 2 byte message - 1st is address, 2nd is data telling it what to do.
Maybe have a couple addresses that are global commands.

This kind of thing
http://www.bliptronics.com/item.aspx?ItemID=88
but with white only?


yes that is the kind of thing I was looking for but in white to get a cheaper price

Quote


Maybe have each board have an LED, current limit resistor, 8-pin ATTiny85, and a single buffer chip.
http://www.ti.com/lit/ds/symlink/sn74lvc1g125.pdf
or make  your own with 2 NPN transistors (back to back inverters)



I'm afraid, this part is far beyond my actual skills.
would this custom solution be cheaper than pre made boards?
I can use a cnc to engrave pcb.

do you know any tutorial that could explain how to wire all this?
thanks for these precious informations, and sorry for my newbie-ness

CrossRoads

"I'm afraid, this part is far beyond my actual skills."
Ok.  Here's what you're looking at. Maybe not this particular 8-pin part, but will be something similar.

"would this custom solution be cheaper than pre made boards?"
The boards are not big  - put an 8-pin DIP on a board, an LED (3mm? 5mm?), two transistors, 4 resistors - how big when done?

"I can use a cnc to engrave pcb."
What, 255 of them?

http://www.bliptronics.com/item.aspx?ItemID=114
price drops with quantity.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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