Monday, February 10, 2014

Addressable LED Jacket

LED Jackets

This is a fast and dirty post to share a few notes on a my LED jacket project. I wanted to do a project using the addressable strips of LED's. I saw that Ada fruit had a lower density strip, only 30 LED's per meter, for $17. I decided to make LED jackets for me and my wife.

We ordered 4 meters. Interestingly the strips came as one continuous piece but you could tell that they were soldered up from several separate pieces. The segments were not always the same length and the solder joints were of varying quality. Look under TUTORIALS in the product information to see some of the projects done using the NeoPixel strips.

This Adafruit guide has everything you could want to know about the NeoPixels and how to communicate with them. My experiments have consisted primarily of modifying the examples given in the guide.

I also used a force sensor to allow the LED's to respond to user input.

We purchase two inexpensive fleece jackets to use the LED's. I pulled Arduino Uno's from other projects for control. The power wiring was done with 20 ga wire that was routed from one pocket and around the back of the jacket using the existing channel provided for an elastic cinch. The power was routed to the bottom of each strip. The power was a 3 AA battery pack with built-in switch. The data lines used wire-wrap wire that was sewn into the jacket.

We purchase 2m for each jacket for a total of 60 LED's per jacket. We decided to use the strips vertically in strips of 10 with 3 strips on the left front and 3 strips on the right front. We used blue painter's tape to define the top and bottom placement of the strips. I recommend mounting the strips a few inches higher on the jacket. I mounted mine as low as possible to match up better with the height of the strips on my wife's jacket (since I am a little taller)

We then placed marks for the strips on the tape for equal spacing. .

I thought this looked like a good adhesive for the project. We considered sewing the strips into the jacket but there were no holes in the pcb's large enough for a sewing needle. (Anyone want to make LED strips with sewing size holes?) The glue tool was used to spread the adhesive on the back of the strips.

We put a generous bead of adhesive on the strip. Stop short of the ends to allow easy access to the pcb for soldering the wires. 

Use the glue tool to spread the adhesive, again keeping away from the last inch or so near the end of the strip.

An oops moment came when I managed to pull off a pad from one of the data lines! Not sure if I over heated the joint (probably) or if I damaged the strip when cutting them. Or I might have just pulled too hard on the wire when working on the jacket.

I had conductive copper tape from another project that I cut down to make a piece small enough to wrap around the end of the pad.

  Bottom view of the tape before soldering.

 A quick dab with a soldering iron and the pad was usable.

Bottom view of the soldered pad.

Here you can see the Uno with the wire-wrap wire connections sewn into the jacket. The Uno draws much less power than the LED strip so the smaller gauge wire was not an issue. Power to the LED's is provided directly from the battery pack by 20ga wire that is not visible in this image. You can also see the Velcro used to mount the Uno.

I ended up writing a sketch to do random color flickering of the pixels. I set one of the jackets to only use red and green to flicker them randomly as a percentage of the total pixels. This made it easy to tune the ratio of lit pixels to dark pixels.

I also used the pressure sensor to increase the percentage of pixels illuminated. This allow me to set the jacket to just light a couple of pixels until I pressed on the sensor. Only a little pressure was required to shift from a few pixels to all of the pixels lit in random changing colors.

I did some pixel dropping effects in orange for Halloween but need to find some photos.

Here is a video of the jacket's scrolling text.

My wife iceskating in her jacket at Rockefeller Center.

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