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Topic: Building an addressable LED strand with WS2801 (custom pcb) (Read 9830 times) previous topic - next topic

bograt

Hello All,

I am working on a project to build an arduino controlled strand of 90 Monochrome addressable (and dimmable) 'pixels', each pixel is made up of 6 x smd 5630 Leds, all controlled by a WS2801. I think I know how to do it now but as I am not very experienced I could really do with some advice.
I want to achieve something very much like this: http://www.adafruit.com/products/683 but after much research I have realized that the only real way to achieve this is to build the pcb's myself.
I have bought some stuff to build pcbs using copper clad board but now I need to build a schematic of the board, this is something that I have not done before but the circuit should be simple enough.
I basically want to recreate this: http://www.adafruit.com/products/683  but with the more powerful 5630 white leds. I have bought 300 leds all laid out on a tape ( http://www.miniinthebox.com/5m-6w-5630-smd-300-led-white-light-strip-lamp-dc-12v_p398471.html ),
I was hoping to cut the led stip into groups of 6 leds and have each group controlled by a ws2801 chip.
Maybe I could just adapt the schematic for this a bit? https://www.sparkfun.com/products/10504 Schematic: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/WS2801-Breakout-v11.pdf
I guess my main concern is that the power usage of the 6 smd leds will be greater than the single rgb led so I would have to isolate the chip from the higher powered leds?
I have been trying to solve this for a while but I am just not that experienced with this stuff so I am struggling to make progress, any help will be greatly appreciated!!
Best

Jules


bograt

O.k, I may be complicating this a bit.
Basically I am willing to pay someone if they can help me build a schematic for this.
I need to build a small pcb 'breakout' using the WS2801 IC to control 6 SMD 5630 LEDs, both on and off and dimmable controls, I will also need to be able to 'daisychain'  the modules so that I end up with a 90 'pixel' strand, all of which are individually addressable.
To keep things simple I would like to use a chain of 6 LEDS cut from a strip like this: http://img.totobay.com/images/xv/201209/20/119613.jpg
Can anyone help me achieve this?
This is a very important project for me so as I mentioned I will be willing to pay, It really does not look all that difficult to achieve, but I simply have very little experience in writing schematics.
Thanks

Jules

elcojacobs

I will put a small RGB LED strip with 8 RGB LED's on 10 cm in my webshop soon. The PCB's are manufactured today.

It has 8 LED's on the front, and 3 TLC5916's on the back, so it is compatible with ShiftPWM.
With the LED's on the front and the drivers on the back, the LED's can be placed very close together (1 every cm). The LED side is also completely flat, apart from the LED's. So you can stick the LED's through a (laser cut) panel.

bograt

Thanks for the reply, I don't quite understand what you are offering... can you elaborate a little bit?
I would be interested to see if the pcb is suitable, can you send me a link?
I really need the 5630 leds because of the colour rendering accuracy which is why I have been avoiding rgb units.
Thanks

Jules

elcojacobs

Oh wait, I did not see that you where using white LED's. I am sorry. I do not have pictures of the PCB yet (next week), but if you want pure white it will not be suitable.

I might be able to make another strip, compatible with different types of single color LED's, but I am very busy at the moment. So if time is critical I cannot help you.


KirAsh4

#5
Nov 27, 2012, 10:56 pm Last Edit: Nov 27, 2012, 11:27 pm by KirAsh4 Reason: 1
Not hard at all.  Just follow the datasheet for the WS2801.  I have a similar "pixel", but with (up to) six 5050s.  I say "up to" because you can also run it with just three.  Basically on the board, I have traces laid out for LEDs 2, 4, and 6, shorting the anode and cathode pins.  If I want to use those LEDs, I just cut the traces and solder the LEDs on.  So by default you start with three LEDs in a triangle configuration.  If you want all six, cut the traces, and add the remaining three.

NOTE: My schematic is based off of the 5050 RGB LEDs which are 20mA per channel (60mA total).  The 5630s are 100mA, SINGLE channel LEDs.

bograt

Elcojacobs, thanks for the help but I have to get things moving with this project. I would still be interested to see the rgb led version you mentioned so update me.

KirAsh4, This is exactly the kind of thing I am after!
I don't have time to take a closer look at this tonight but I will take a look tomorrow, If you would be happy to help me tweak this to suit my purposes I would be more that happy to pay you for you time!
I had a look at the data sheet but I am honestly not that proficient in electronics so I was unable to figure it out, If you take me up on my offer I will explain in more detail what exactly I need.
Thanks

Jules

KirAsh4

Can I ask what this is for?  90 pixels of 6 LEDs each, each LED potentially up to 100mA, that's 54 Amps.  Not knowing what this is for, I can't decide whether this is over kill in brightness or what.  But, as a comparison, I created a 160 pixel display last year.  Each pixel was a single 5050 LED which runs up to 60mA with all three channels lit (white).  That's a total of 9.6 Amps.  It was full color, single LED pixels, and very bright sitting in my window:

http://www.youtube.com/watch?v=-3ex1k8f_Nk

bograt

Yep that does sound like a lot, It is actually for photographic purposes, Its is really to be able to control lighting distribution, but brightness and light color is fairly important.
I bought two lengths of tape like: http://img1.buyincoins.com/gallery/1m-led-strip-white-04_01.jpg , each with 300 leds.
I was intending to use these cut into lengths of 6 because it saves me re'soldering all leds and resistors into groups, Also, I know that I can run 300 of them on a single power supply so (I though) power draw would not spiral out of control.
The setup you did looks amazing, and in fact very bright, but I was trying to avoid rgb pixels because of color purity issues.
I just read the back of the power adapter I was given to run these 5630 strips and it says output: 12v--2A...  something seems wrong here.
Do you think the adapter is seriously under powering them? or maybe the resistors are over resisting?
I have clearly missed something here because the data sheets say: output 50 lumens/led, multiply that by 300... 15000! That's way more than I need anyway.
Maybe I will re-think using 6 leds per module, I do need alot of light but maybe 4500 lumens will be enough (90x50 lumens)

Jules



KirAsh4

It's possible that the design itself is limiting the LEDs.  Looking at the strip, it looks like there are 3 LEDs per segment, however I only see 2 resistors per segment.  Not knowing how they are wired together, I can only make assumptions here.  However, let's assume they are connected in series, that means that you have 3 LEDs with a voltage drop of 3.2V (nominal) for a total of 9.6V of voltage drop.  So the 12V supply is correct.  However, the 2 Amp is questionable.  Not knowing how the strips are assembled and where the resistors are, it's really hard to figure out what they're trying to do.

This is my number one pet peeve with these things, they're never what they say they are.  Which is why I resort to making my own.  Sure it takes more time, and possibly a bit more expensive, but in the end I will end up with a product which I know works the way I designed it to work.

I have a lightbox made from LEDs (hey, I take photos as well).  I used RGBW LEDs though.  This allows me to control the light temperature quite easily, and I can also use it as a color flood.  But, be prepared for the sticker shock on those LEDs ...

Here are two datasheets for you to consume:

http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXML_Color.pdf

http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampMCE.pdf

bograt

Wow, those look nice... but damn they look pricey (I need 90!). In all honesty It is certainly on the cards for an upgrade, the colour control would be amazing
I think you are right about doing this from scratch, I only went for the 5630 strips to play around with and because they are so cheap.
I guess from this point it might be a good idea for me to design a pcb based on the smd 5630, I can then possibly upgrade to the cree colour leds when I have more of a system in place.
Do you think you will be able to help me design a pcb that I can 'toner transfer' onto copper clad board? Again I will pay you for your time!
I have been trying to figure out how to make this for many months but I think I am finally getting somewhere, I just don't have the know-how to design the schematic (I can certainly build it though)
Thanks for all your input

Jules

bograt

Or I could always use a slightly cheaper white cree LED if its more suitable

bograt

I can't edit my previous post so I will just have to write new ones...
I am liking the look of this: http://www.cree.com/led-components-and-modules/products/xlamp/discrete-nondirectional/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XlampMLE.pdf
In particular: CREE - MLESWT-A1-0000-0003E3 (series), The specs look perfect and I can source them very easily.
How easy do you think it would be to design a pcb like the schematic you provided but using a single one of these per board?


KirAsh4

Those LEDs have a forward voltage of 9.6V (series) driven at 167mA.  You'll need at least 12V to drive a single board.  A better solution is to use the parallel version, however no one seems to stock those for whatever dumb reason.

But yeah, I can certainly build a board that has one of these on it, with a WS2801 and necessary components to drive the LED.

bograt

DAMN IT! There are some things I just don't understand about electronics...
I realized yesterday that the best option for my project would be to utilize all 3 outputs on the WS2801 and run 3 seperate LEDs (but never at the same time, just one after the other)
So my ideal design is very similar to the schematic you originally provided, just with 3 seperate Leds rather than rgb channels.
There are still some things I just don't understand technically but if you think there is a way to make this work with these, or some similar LEDs (3 per board) then we can talk money, and I will paypal you a deposit!
By the way, I was maybe thinking of powering this with a computer power supply...? (like what others seem to so)
Thank you so much for your input, this is invaluable to me!

Jules

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