Lilypad + Propeller Chip

I recently purchased Sparkfun’s Lilypad bobbin because I’ve always been fascinated that you could integrate circuits into clothing. However, Auduino-happy Sparkfun doesn’t make a Propeller board for the Lilypad system, so it looked like I’d have to make my own. It was tricky finding something small enough that has through holes with no pins in them, but I eventually settled for Jeff Ledger’s Protoboard hack. I’m sorry that I have no pictures of this hack yet, but I may add some later. I didn’t leave all the space around the edge of the chip as in Jeff’s hack, but I cut down to the 2 rows of connected pins to decrease space. I left enough space at the bottom to solder the programming header and connected it as shown on Warrenty Void.

I found the Propeller setup worked when powered with a 3V coin cell battery.

Now let’s move on to the interface. As cool as single LEDs look, I wanted something, well, MORE. I was thinking a small display. Preferably, an LED matrix. However, once again, Sparkfun doesn’t make one (I’m not bashing Sparkfun now, just illustrating my love of doing it myself). Since I only had the bobbin and thread, I decided to attempt soldering 25 SMD LEDs to the bobbin, which is actually a little protoboard. I first took all of the thread off of the bobbin, which takes longer then you would think, as there is about 5 times more thread on the bobbin than is shown in the picture on the Sparkfun website. I then started to solder the LEDs in a 5X5 matrix. The cool thing is, all the holes are connected by traces, so if you cut the traces right, you only need a few wires to make the matrix!
To solder the LEDs to the protoboard, you put a small solder ball on one hole, then move the SMD LED over to it with your finger while keeping the solder molten. It should bond to the LED. If it needs adjusted melt the solder again and move the LED into place with your fingernail. Now apply solder to the other side, but you don’t need much, as most of it goes through the hole anyway.
Now repeat this step 24 times. To get the layout you want, attach them so that all columns have the polarity facing the same direction, and all rows have alike polarities facing each other (e.g. + to +, – to -, etc). After you get them soldered, (I did it before they were soldered) cut the traces. You want to cut the spaces in between the columns of negative polarity, and the spaces between the rows of positive polarity. Now for wiring. Connect all the positive ROWS together with short wires.
Tada! After hours of work you have a small but cool looking SMD LED matrix, ready to be sewn into a hat or shirt pocket. And best of all: It’s PROPELLER POWERED!!!
Here’s my result:

One more note: About the conductive thread. It looks good, it feels good, but it is impossible to work with. It doesn’t fit through the holes in the protoboard easily, when heat from solder is applied it dissolves, and when you try to wet it to straighten it out it just rolls off. It’s also hard to find a needle that it fits through, so if I ever actually get it embedded into something, it will take days to make all the connections.
Other than that, this is a pretty cool project!

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2 Responses to Lilypad + Propeller Chip

  1. Steve Neets says:

    So, there’s a Propeller and a lilypad/matrix, but no interface between the two?

    I think you need a low-temp soldering iron (500deg) for the conductive thread (God save us).
    Also, there is a tool we call “tweezers”, they come in several forms. They are very handy for holding small bits and, in this case, not burning yourself, but you probably like that.

  2. admin says:

    Oh, there is a communication between the 2. I forgot to mention in the article that I have successfully communicated between the lilypad board and the Propeller setup. I just don’t have a good object available for it yet, so I figured I would add a writeup on that when the object was complete. I’ll add this in the article so that others aren’t confused on the subject. Also the LEDs are low power so the Propeller needs no external circuits to drive them, as they would with a larger LED. I just thought that it would be interesting to see it working.
    It’s about time that I actually get a good soldering iron with adjustable temp. I’ve been using junk soldering irons for several years, and going through about 2 per year. I use one every day, so I’ll consider it. :-)
    Also, I’ve found that usually when I use tweezers I squeeze them too hard while soldering to the part and then the LED will shoot off to where I can never find it. I managed to avoid getting burned while I was working on the project, though.

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