Go Down

Topic: how to drive 12v 1 W rgbLED with COLORDUINO? (Read 1 time) previous topic - next topic

Mengo

Hi there,

I recently bought a COLORDUINO, and I find it very nice.

I was wondering how could I build a 'buffer' stage, in order to drive 64 x 12V 1W RGB led.

Finding the right 12V power supply won't bother me, but what would be the best choice between MOSFET or simple transistors or an array of these: http://www.ic-on-line.cn/view_download.php?id=1494504&file=0248%5Culn2001_39642.pdf ?

or should I go with something like these? http://www.onsemi.com/pub_link/Collateral/CAT4101-D.PDF

I can't really figure out how to connect any of these solutions with the colorduino.

It would have been much simpler with a classic TTL signal and common ground configuration. But what's the story in this situation?

Hope someone can help me, and spark ideas to others

thanks in advance!

Grumpy_Mike

Quote
I recently bought a COLORDUINO, and I find it very nice.

A link would be good so we can see what you are on about.
The constant current drive would be the way to go, you will ned one chip per LED, how many have you got? the darlingtons will not help you here.
Are you dealing with a multiplexed array? If so then it is tricky to increase the drive without pulling it all appart.

Mengo

ok, here is the link of the ARDUINO compatible board we are talking about, the COLORDUINO:

http://iteadstudio.com/product/colorduino-v1-3-preview/


and here you can find schematics both from the whole board, and from the led driver chip itself:

http://iteadstudio.com/produce/colorduino-schematic-and-demo-code/


It this then clear, that something simple like this won't work:

http://www.google.it/imgres?um=1&hl=it&biw=1280&bih=911&tbm=isch&tbnid=stBAFyL4LC79EM:&imgrefurl=http://la.thepublicschool.org/class-notes/256&docid=W9QDxeWngNM8ZM&imgurl=http://la.thepublicschool.org/sites/la.thepublicschool.org/files/multiple_leds2.jpg&w=871&h=441&ei=x2RgT6q1LcGGswa87sy7CQ&zoom=1&iact=hc&vpx=169&vpy=560&dur=1815&hovh=160&hovw=316&tx=171&ty=92&sig=115366282750720556699&page=2&tbnh=108&tbnw=213&start=31&ndsp=25&ved=1t:429,r:15,s:31

as there is no common ground, but both ground and positive are switched on and off by the controller.


Maybe something with NPN transistor on the 8 Vcc pin(LED's common anode), and PNP transistor for the 24 RGB pin?

mumble mumble...   :)

Grumpy_Mike

Quote
and here you can find schematics both from the whole board, and from the led driver chip itself:
http://iteadstudio.com/produce/colorduino-schematic-and-demo-code/

How is this for you? I only get a PDF file with squares and lines on it. No part numbers, no pin numbers, no IC signal names. It could be the schematic for anything. I am running a Mac so it might be an odd sort of Widows PDF.

Quote
as there is no common ground, but both ground and positive are switched on and off by the controller

Yes that is how a matrix works. See my page:-
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html

Quote
Maybe something with NPN transistor on the 8 Vcc pin(LED's common anode), and PNP transistor for the 24 RGB pin?

It is not as simple as that because you need something to limit the current through the LED. A resistor will not cut it for a 1W LED because the forward voltage drop of these is not stable. Therefore you need something like a constant current supply to limit the current as well as hefty drivers. FETs will be better than transistors at these values.

Mengo

Quote
How is this for you? I only get a PDF file with squares and lines on it. No part numbers, no pin numbers, no IC signal names. It could be the schematic for anything. I am running a Mac so it might be an odd sort of Widows PDF.


well, it's not the best diagram I have ever seen, but still you can get an idea of the schematic. The most usefull link is mabe the comprehensive 163 chip datasheet, wich at least give you an idea of how the maytrix is driven.



Quote
Quote
as there is no common ground, but both ground and positive are switched on and off by the controller
Yes that is how a matrix works. See my page:-
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html


ok! so maybe you could suggest an amplifier for your circuit, and that could apply to mine and others as well!! :)



Quote
Quote
Maybe something with NPN transistor on the 8 Vcc pin(LED's common anode), and PNP transistor for the 24 RGB pin?
It is not as simple as that because you need something to limit the current through the LED. A resistor will not cut it for a 1W LED because the forward voltage drop of these is not stable. Therefore you need something like a constant current supply to limit the current as well as hefty drivers. FETs will be better than transistors at these values.



well, to be honest my LED modules already have an internal resistor in order to make them work with 12V, so maybe this won't be a problem..

anyway you think something like this could work?

http://www.sparkfun.com/products/10213

or you suggest a normal FET?


thanks again!!

as I thought, it's not so easy to 'boost' a matrix then, but I need to do it!! :)

Grumpy_Mike

Quote
anyway you think something like this could work?
http://www.sparkfun.com/products/10213

That will work for one of the FETs, the one that pulls down, it is an N-channel one. You will also need a P-channel FET to source the power. As you want to drive 12V then the gate of this FET will have to be driven through a transistor or n-channel FET to get the 12V to 0V signal to turn it on and off.

Quote
my LED modules already have an internal resistor in order to make them work with 12V,

So again lack of information hampers a sensible reply. What LED have you got? Module, strip, component, just what?

Quote
well, it's not the best diagram I have ever seen, but still you can get an idea of the schematic

No you can't it is total pants. It is dishonest of the person to put it up and I would have nothing to do with him if it were me. At least a complaint would be going in. I assume it is a crude attempt to stop anyone copying the design, but something like that is deplorable.

Mengo

Quote
That will work for one of the FETs, the one that pulls down, it is an N-channel one. You will also need a P-channel FET to source the power. As you want to drive 12V then the gate of this FET will have to be driven through a transistor or n-channel FET to get the 12V to 0V signal to turn it on and off.


ok, so, any suggestion for the p-channel fet?


Quote
Quote
my LED modules already have an internal resistor in order to make them work with 12V,
So again lack of information hampers a sensible reply. What LED have you got? Module, strip, component, just what?


as already said, I have led modules.

to better understand let's say it's something like these:
http://led-modules.zapled.co.uk/rgb-led-full-colour-modules

but my question is about any 12V rgb led module, as the question here is not how much hefty the transistor must be , but how to connect it to a matrix driver.


Quote
No you can't it is total pants. It is dishonest of the person to put it up and I would have nothing to do with him if it were me. At least a complaint would be going in. I assume it is a crude attempt to stop anyone copying the design, but something like that is deplorable.



to be honest I don't know about iteadstudio.com policy, but maybe this is something we should discuss somewhere else.
I was just wondering how to have fun with this (and maybe any other) matrix cirucit board, if someone can help...


Grumpy_Mike

Quote
as already said, I have led modules.
to better understand let's say it's something like these:
http://led-modules.zapled.co.uk/rgb-led-full-colour-modules

Sorry but if you have a module like this then you can't connect them up in a matrix.

evanrich

I agree 100% with Grumpy_Mike about the schematic PDF.  That is by far one of the worst I've ever seen.   All the capacitor values are "???" and every resistor is "0R".....It's like getting someone 90% of a solution, then giving them the finger on the last 10%.    The layout is mediocre, not very well organized, some part #'s/values are missing, sheet info is missing,  some symbols are hard to understand.    This thing is crud.
My first major project (looking for people who would like to help contribute) Bluetooth Sure 32x16 LED Displays!: https://github.com/evanric

Go Up