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Topic: Building my own ws2801 string (Read 4811 times) previous topic - next topic

AceoStar

So I have this map project that I'm working on and I bought a prebuilt string of ws2801 LEDs. So far the project is going great and I'll be done with the prototype shortly, but in an effort to build a more svelte end result, I'd like to look into building my own string.  To explain, the prebuilt strings come with bulky cases, I need something that I can stick through my map, and do the wiring on the back side of the board(prob posterboard). This will allow me to place more LEDs in a small area and damages less of the map for removal (no big hole, just the LED legs).  I'm thinking the legs will come through, I'll solder them to some wire and run it over to a breadboard with the chip attached and linking back out to the next led.

Should I just buy a bunch of ws2801, http://www.aliexpress.com/item/Free-Shipping-100-PCS-LOT-X-Original-WS2801SO-WS2801-SOP/666372104.html, some RGB leds and let my imagination go wild? Is there anything I should be concerned with? I assume I need resistors? Common cathode or anode? Is the size of the chips going to give me problems, they seem small.

Here is the data sheet http://www.adafruit.com/datasheets/WS2801.pdf

KirAsh4

Follow the datasheet.  This is something I have done, it's not rocket science.  I used 5050 RGB SMD LEDs though.  The attached image shows the LEDS in the various stages:

Directly above the pencil: blank boards, front and back.
At the very top is one side of the board with the WS2801, 3 resistors, and a capacitor (each in a corner).
At the very bottom is the other side of the board where you see the 5050 RGB LED attached.
Directly below the pencil are the individual pieces once I cut them apart.

The second picture is a closeup of the IC side of the board, where you can see the WS2801, resistors, and capacitor in the corners.

The row of four holes on either side is the data/power cable, a 4-core ribbon cable, that allows me to daisy chain them to whatever length.

If you want to use through hole LEDs, you obviously can't use this method as everything on here is SMD.  These LEDs are 5x5mm by the way.

Ultimately the strings I created ended up in my window, which you can see here:

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

Why did I do that when I could've bought ready made strings?  I wanted to learn to work with double sided SMD by doing it myself.  I'd say I was successful ...

Lakes

I like this, would make a good project for those wanting to try smd soldering.

Is the PCB design available?

KirAsh4

Sure.  I also have some of them left over still, so if you're just going to try, I don't mind dropping one or two in the mail for you.  They're 4x3, so each board will give you 12 "pixels" to work with.

I attached my Eagle files. You should be able to open it as I left it as a single schematic (the actual project has multiple schematic pages.)  There are part numbers listed on the schematic page.

Couple of caveats to note:
- Both the resistors as well as the capacitor pads are 0402, however on the physical boards I used 0805.  They still fit on the pads with no problem.  However, I'm also doing a reflow method on the IC side, so the solder paste gets hidden underneath the components.  If you are hand soldering them, I would recommend changing the pads to larger ones so you have something for your iron to tack on to.

- The spacing between each individual pixel is 1mm wide and while I put drill holes in the connecting bridges, I found out afterwards that the FR4 material is rather tough to snap off with the hole spacing I used.  Ultimately I used a Dremel cutting tool and sliced through the bridges.  My cutting wheel is 0.8mm wide so it was a near perfect fit between the pixels.  If I had made an updated design I would've put the holes closer together and used only 3 instead of 5.

- The spacing on the holes for the ribbon cable is 1.5mm.  You need a fine tipped iron to get to them.  I used a 1.27mm pitch ribbon cable like this one from Digikey.  Stripped the ends and separated them just a bit so they line up with the holes.  I wanted a thinner cable versus a 1.5mm pitch.  This worked fine, no issues.

- And lastly, but most important, I made these boards through BatchPCB because they were able to do the contour cutting (notice each corner is rounded and the pixels are individually cut out except for the bridges.)  So this made it more expensive compared to say Seeedstudio or iTeadstudio or others.  If you want to go cheap and have Seeed or iTead do them for you, you'll have to do a lot of cutting afterwards, but the advantage is you can get it on much thinner material.

Lakes

Thanks for sharing! <thumbs up>

AceoStar

Awesome information so far in this thread! I feel like I'm starting to have a better understanding of what I'll need to do, but since we're mostly talking about SMD I still have some gaps.

In order to have my "loose" pixels, I'd need to have all of these parts wedged into a small area. I could put the chips on a breadboard though, with the resistors and capacitor and just plug each long LED wire into the breadboard :/

Or I guess I could build something like you've shown here but instead of connecting the LEDs directly to the chip, I'd run them via a wire for each leg of the LED.  I only need about 50 RGB LEDs so four or five of these should do the trick.

Sorry to ramble on, hoping my random thoughts will inspire someone to set me straight :p I'm pretty new at this so I apologize if my questions aren't up to par :p

KirAsh4

You really want to keep the LED close to the IC.  Running long wires between them can lead to issues.  You could use regular through hole LEDs with this if you change the layout to allow for the legs to go through, or you can bend the legs and solder them as if they're SMD parts, just on the surface of the board instead of through it.

On the other hand, having SMD lights like I did means you can put the LED behind the map without needing to poke a hole.  Might be nicer ...

fungus

I bought some of these a couple of weeks ago and they work great:

http://www.ebay.com/itm/370729430086

The WS2811 is a little bit trickier than the WS2801 but still quite easy.

The PCBs have resistors, capacitor, etc. built-in, ready to go. The ones I received are smaller than shown there - about 9x13mm.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

AceoStar

#8
Mar 20, 2013, 03:38 pm Last Edit: Mar 20, 2013, 05:22 pm by AceoStar Reason: 1

You really want to keep the LED close to the IC.  Running long wires between them can lead to issues.  You could use regular through hole LEDs with this if you change the layout to allow for the legs to go through, or you can bend the legs and solder them as if they're SMD parts, just on the surface of the board instead of through it.

On the other hand, having SMD lights like I did means you can put the LED behind the map without needing to poke a hole.  Might be nicer ...


I see. Thanks for setting me straight on the LEDs being wired at a distance vs closer to the actual chip. My first vision of this project involved lots of TCL5940 but I would still end up running the LEDs 2-5 feet away from the chip.

You mention being able to put the LED behind the map. Do you mean put it behind the map and have the light shine through? I hadnt thought of that, but it could potentially work, however I do have like 12 pins to put in florida so even on a 5 foot map I need a bit more standout per pixel.

Something like this http://www.ebay.com/itm/370729430086, (in a ws2801 version) may work for me, I could run the LED through the paper, stick it into the chip on the backside of the board, and then connect each chip together. Seems kinda clunky tho, maybe I'll have to cut the hole in the map :/

Or this looks close too http://www.freetronics.com/products/rgb-led-module#.UUngu6LVD2s but 10 per LED seems kinda steep.

KirAsh4


Or this looks close too http://www.freetronics.com/products/rgb-led-module#.UUngu6LVD2s but 10 per LED seems kinda steep.


That is exactly the same thing as what I created.  And yes, $10 per pixel is very steep in my opinion.  Mine came out to just a little over $1 per pixel.  Like I said, you could just take a regular 3mm through hole LED, bend the bottom 3-5mm of the legs at a 90 degree angle and solder that to the boards I created.  You just need to sort out the red, green, and blue pads and the cathode goes opposite (on any one of the three pads.)  Not that hard to do.

AceoStar

#10
Mar 21, 2013, 12:44 am Last Edit: Mar 21, 2013, 01:31 am by AceoStar Reason: 1
Now for some even more basic questions. How did you go about creating those boards? I've heard (and seen you guys) talk about Eagle. Do you just load up the sketch in eagle and then have someone fabricate the parts? How expensive is that normally? I assume to get them down to $1 a piece, it would have to be pretty cheap or did you get some bulk discount?

You mentioned putting the LED behind the map, were you thinking of the light shining through the paper or something else? Super dumb question, but I shouldnt have any problems with conductivity when plugging a LED through the paper and then posterboard before connecting to the chip should I?

KirAsh4


Now for some even more basic questions. How did you go about creating those boards? I've heard (and seen you guys) talk about Eagle. Do you just load up the sketch in eagle and then have someone fabricate the parts? How expensive is that normally? I assume to get them down to $1 a piece, it would have to be pretty cheap or did you get some bulk discount?


Eagle (http://www.cadsoftusa.com/) is a schematic and PCB design software.  It has nothing to do with Arduino sketches, or Arduino in general.  If you read the datasheet for the WS2801, it will have example schematics in it for different configurations.  The typical layout is all you need (without the load resistors.)  Or, you could also grab the schematic and board files for the same thing from SparkFun here https://www.sparkfun.com/products/10504

I merely shrunk the design for my purposes to 11x15mm.  I could've gone smaller but for me, this was small enough.


You mentioned putting the LED behind the map, were you thinking of the light shining through the paper or something else? Super dumb question, but I shouldnt have any problems with conductivity when plugging a LED through the paper and then posterboard before connecting to the chip should I?


Yes, shine through the paper if using SMD LEDs.  If you're using regular through hole LEDs, you can use 3mm ones and poke them through.  Paper doesn't conduct electricity (not exactly 100%, it's resistance is just very very high.)

KirAsh4


Now for some even more basic questions. How did you go about creating those boards? I've heard (and seen you guys) talk about Eagle. Do you just load up the sketch in eagle and then have someone fabricate the parts? How expensive is that normally? I assume to get them down to $1 a piece, it would have to be pretty cheap or did you get some bulk discount?


I forgot to answer the other part of your question:

Each board holds 12 pixels in a 4x3 grid.  One order of 10 boards (from iTead) is $9.90.  So, each board is $0.99.  Divided by 12, that's $0.0825 per pixel.

The LED, bought in bulk, was something like $0.67.  The IC, again, in bulk, was $0.13.  Resistors were $0.015, capacitor was $0.014.  Add it up and you get $0.9115.  That's based on buying everything in bulk though.  I rarely buy less than 5,000 when it comes to thing like resistors and capacitors.

KirAsh4

#13
Mar 24, 2013, 09:02 pm Last Edit: Mar 24, 2013, 09:06 pm by KirAsh4 Reason: 1
While these aren't RGB pixels, the process is the same for any panelized design I create, including the layout for the WS2801 + SMD RGB pixel in this thread.  I needed to make 630 bright green LED pixels and rather than buying the LilyPad pieces (https://www.sparkfun.com/products/10046) which would've cost me upwards of $500, I decided to make my own.  On a 50mmx50mm piece I can cram 23 of them: a grid of 7x3 plus two extra to fill the rest of the board.

Production of boards was $30 + $5 shipping.  LEDs and resistors just over $200.  My time: priceless.  :)

Here's me cutting a single board into pieces, takes me a little over 2 minutes each (I already trimmed off the extra two that are along the top edge of each board).  I should point out that these are 0.8mm FR4 boards, however the WS2801 pixels I created above were done on 2mm FR4 boards.  Cutting is just a bit slower for those.

http://www.youtube.com/watch?v=C_2T23rSzJo

Lakes

And he still has all his fingers!! :D

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