Building an addressable LED strand with WS2801 (custom pcb)

And final module size?

Similar size to yours by the looks of it, around 30mm x 30mm. The leds in particular are really tiny so I don't think that will be a problem (3.2mm x 3.5mm to be exact).
The other thing is the header(s), I had trouble figuring out if what I was looking at was suitable on farnell, maybe its best to go for the same ones you used.

I just used regular rectangle headers, SMD mounted. Something like this:

http://uk.farnell.com/samtec/tsm-104-01-s-tm/header-2-54mm-smt-12way/dp/2044053

I specifically used a 2x6 header for several reasons. Two rows so I have a good grip on the board and less chances of ripping it off. And 6 pins so I can have 2x VCC, 1x DATA, 1x CLK, and 2x GND. Duplicate it for the second row.

Then I used ribbon cable plugs to connect to the boards, like these:

Ok they look good, they are not £3 each are they?! that would set me back more than the 540 leds! does it mean for 5?
2 rows makes sense to me as well...
What would be the next step then? build a schematic?

Eh, that specific one seems a bit high yes. There are others, just search for board headers, rectangle, 2.54mm pitch, 12 pins, 2 rows, SMD mount.

I might just try to find some bulk packs from china, might save me alot of money in the end...
So whats next? Is it important to know exactly what components to use before making the schematic?
btw, I have just got my 'led pixels' Overview | 36mm LED Pixels | Adafruit Learning System so I can finally start playing around with the code for the ws2801 :slight_smile:

No, the schematic is simply symbols. Actual parts (as far as whether it's a through hole or SMD, and what size) is mainly done on the board side. So either you figure out what parts you want to use and tell me, or I build the board and tell you what parts to get (this is what I normally do.)

Code for WS2801 is easy. Download FastSPI and run the testleds sketch (after adding a setDataRate(2) delay before the .init() call.)

Ok,
When you say build the board, do you mean 'theoretically', or mean to actually build one?
I'm sure you would be better at picking the parts than me so maybe that's a better solution, the only parts I need for sure are the leds, apart from that I guess reasonably cheap smd parts are what I'm after,
not so fussed about the size... I have played around with some 0603 resistors, I can work with them no problem.

Code for WS2801 is easy. Download FastSPI and run the testleds sketch (after adding a setDataRate(2) delay before the .init() call.)

will do, thanks

No, I mean building one in Eagle. Ready to go to a fab house of your choice.

Ok, perfect!
I will be using the avago leds and the same header dimensions you used, all smd parts, and 12v input. Apart from that I guess the layout can dictate the rest.
Just let me know what else you need
Thanks

Jules

Aight. I'll work on it over the weekend. I need to re-create the Avago LED in Eagle first and go from there. Different pads and dimensions. Do you have a preference on size for the other components? For example, do you prefer 0805 resistors or can you work with 0402?

Amazing! thanks.
I guess I can work with 0403 but I don't really have a preference, whatever you would do really, considering cost as well.
This is really exciting for me, thanks

Jules

Cost difference on one specific one:
0402: £0.011
0603: £0.007
0805: £0.024

Depending on the actual resistor needed, I may or may not be able to get the size I want to use and will have to use a different one. For example, sometimes I can't get a 10K in 0402 size and have to use 0603. And I'm trying to stick with Farnell since you said you're in the UK.

That's fine, if there's so little in it I am not so concerned, equally, I am not going to mass produce this so I am not so worried about variations in size.

But, but, but, mass producing them will be cheaper! grin

Seriously though, buying 50 of the same resistor is cheaper (as a single unit) ... I have yet to buy less than 100 when it comes to stuff like that. I'll always find a use for them in whatever future project I come up with.

In your case, if you don't foresee having a use for them in the future, then yeah, buying them in small quantities will be the way to go.

hahaha, Your right
I will have to buy 540 Leds minimum so I guess its bulk in a sense, but the boards will still be assembled by hand so I guess from a mass manufacturing point of view component size wont make such a difference...

Hi Kirash,
Did you manage to do anything with the pcb layout?
Best

Jules

I'm dead in the water here

Kirash,

I can see now that this thread is dead but I would like to thank you for all the help you gave me for getting to this point, Cheers!
Best

Jules