LED Grid: RGB, The Evolution
2020-Jun-01, Monday 03:00 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
chebeThis started with wanting a new outfit for EMFcamp. EMFcamp ended up being cancelled this year, but the project had begun (in earnest at SciHackDay), so I had to finish it (at campGNDd). At least I'll be real prepared for 2022.
Once upon a time I made a 7x7 blue LED matrix grid top, with LED beads and conductive thread. (I've since misplaced it. *sad face*) I wanted something similar, but green, and that could survive hanging out in a field for several days. I've learnt a few things in the last *checks* ten years, so wanted to upgrade things a bit.
First things first; RGB LEDs. Single colour LEDs have their place, but the limitations are rather absolute. NeoPixel Mini Buttons are the smallest breakouts available. They come in five packs (Adafruit / Pimoroni), and in fifty packs (Adafruit / Pimoroni). You simply snap them apart, and chain them up, to use. The solder pads are on the back, the usual 5V in/out, GND in/out, Data in/out.
I did some rough calculations, involving likely power source and rough area of the front of my tshirt, and decided on a 9x9 grid. Although 9x9 doesn't seem that big an increase over 7x7 it is actually 81 versus 49, and instead of two solder joints (to attach the crimp beads) per LED there are now six. It is a fair bit of work.
And if I'm doing all that soldering anyway why add the extra work of attaching everything with conductive thread? Which is uninsulated and likely to short while dancing. This is where Silicone wire (Adafruit) comes in. It is flexible, and insulated. All my dreams come true.
To begin I draw out a 9x9 square grid, all the intersections 1.5" apart, on some paper as a guide. Then I place the buttons down and get measuring. I need lengths of silicone wire about 3.5cms. First I solder the centre Data pins, in nine runs of nine. Make sure to connect Data out to Data in the whole way.
Then I soldered the Power and Ground lines. Now is a good time to test each string to make sure they work as expected.
This process resulted in quite a lot of irregularity. If I do this again I'd make a small jig to hold the NeoPixels and predefine the length of the wires more exactly, with less effort.
Next the nine strings get connected into one long string. Start with the Data pins (double check going Data out to Data in), with lengths of wire about 7cms. Then the inner wires, about 5.5cms. And the outer wires, about 8cms.
Connect all three pads (Power, Data, Ground) on the first NeoPixel, but only two (Power and Ground) on the last NeoPixel. I made the wires on the last NeoPixel long enough to run around the outside of the grid and meet up with the wires into the first NeoPixel. This is to help power be more evenly distributed through the long string of NeoPixels.
We now have many exposed solder joints involving thin wire. I want to insulate them (from body sweat, spills, etc), and provide some physical support. You can hot-glue them, but as I'm going to wear this I don't want to worry about body heat softening the glue. So I'm going to Sugru the backs. Little round balls of Sugru, pressed into the backs to make discs. Leave for two days to cure.
I want to add more support, so I also add little crescents of Sugru to the points the wires meet the NeoPixel boards, from the front. Leave to cure for two days.
Okay, the NeoPixel string is basically done. But we need it to be a grid. To help the NeoPixels keep the shape we want, and to help support the weight, I made a square, with a cross inside it, from cotton webbing/stay tape sewn together. But wait, how am I supposed to wear it? I want this to be removable, not permanently attached to any one garment. So I made sure to sew loops into the ends of each tape as attachment points.
Lining up two flexible things is awkward, but I found hair grips/bobby pins worked great to hold everything roughly in place while I hand sewed the wires to the tape. You want to make sure that it is the tape that is taut, not the wires, to reduce pulling.
With the wires sewn to the tape, weave the long wires from the last NeoPixel through the other wires, along the outside edges of the grid, on the way back to the first NeoPixel.
Now it's an actual grid. But it needs to connect to a microcontroller. Best practice says to use a resistor (300-500 ohms) on the Data in line. So I added a tiny three-strip wide stripboard before the first NeoPixel. Make sure to break the board connection beneath the resistor. Then I soldered the Data line to connect with the resistor, both Ground wires into the one line, and both Powers into the other line. On the other side I soldered a three-pin connector (e.g. 3-pin JST). I then covered the stripboard with two layers of heat-shrink tubing.
Okay, moment of truth, time to test. I used an Adafruit Flora, the basic strandtest example, and turned it on. Oooh, pretty.
When I say silicone wire is flexible, I really mean it. It can bend and conform to surfaces with almost no memory. And any memory is easy to correct. Here is my grid wrapped around a plastic tube.
And here it is twisted around itself many times in the middle. (This is probably not the best photo, the strandtest example had moved on to the blinking rainbow section, those NeoPixels are intentionally off, not shorting.)
Here it is worn (under a semi-sheer top), off. You can see the lumps of the NeoPixels themselves, but nothing is constricted or compressed. The grid is conforming to my body, rather than the other way around.
And here is it worn, and on. Again you can see the grid conforming to my body rather than constricting it. You can also see that I only have it attached at the top two corners. The grid is so flexible that its own weight (91g) is pulling it down in the middle. (Easily corrected by attaching more points of the top tape to the outfit.)
So it's flexible, it's versatile, but how durable is it? This is the first version, so we'll have to wait and see.
Once upon a time I made a 7x7 blue LED matrix grid top, with LED beads and conductive thread. (I've since misplaced it. *sad face*) I wanted something similar, but green, and that could survive hanging out in a field for several days. I've learnt a few things in the last *checks* ten years, so wanted to upgrade things a bit.
First things first; RGB LEDs. Single colour LEDs have their place, but the limitations are rather absolute. NeoPixel Mini Buttons are the smallest breakouts available. They come in five packs (Adafruit / Pimoroni), and in fifty packs (Adafruit / Pimoroni). You simply snap them apart, and chain them up, to use. The solder pads are on the back, the usual 5V in/out, GND in/out, Data in/out.
NeoPixel Mini Button PCBs
Photo by chebe
I did some rough calculations, involving likely power source and rough area of the front of my tshirt, and decided on a 9x9 grid. Although 9x9 doesn't seem that big an increase over 7x7 it is actually 81 versus 49, and instead of two solder joints (to attach the crimp beads) per LED there are now six. It is a fair bit of work.
And if I'm doing all that soldering anyway why add the extra work of attaching everything with conductive thread? Which is uninsulated and likely to short while dancing. This is where Silicone wire (Adafruit) comes in. It is flexible, and insulated. All my dreams come true.
To begin I draw out a 9x9 square grid, all the intersections 1.5" apart, on some paper as a guide. Then I place the buttons down and get measuring. I need lengths of silicone wire about 3.5cms. First I solder the centre Data pins, in nine runs of nine. Make sure to connect Data out to Data in the whole way.
Nine strings of NeoPixel Mini Buttons, nine NeoPixels in length, with only centre Data lines soldered using black silicone wire
Photo by chebe
Then I soldered the Power and Ground lines. Now is a good time to test each string to make sure they work as expected.
This process resulted in quite a lot of irregularity. If I do this again I'd make a small jig to hold the NeoPixels and predefine the length of the wires more exactly, with less effort.
Same nine strings, now with Power and Ground lines soldered using black silicone wire as well
Photo by chebe
Next the nine strings get connected into one long string. Start with the Data pins (double check going Data out to Data in), with lengths of wire about 7cms. Then the inner wires, about 5.5cms. And the outer wires, about 8cms.
Same nine strings made into one long string with curved wire connections
Photo by chebe
Connect all three pads (Power, Data, Ground) on the first NeoPixel, but only two (Power and Ground) on the last NeoPixel. I made the wires on the last NeoPixel long enough to run around the outside of the grid and meet up with the wires into the first NeoPixel. This is to help power be more evenly distributed through the long string of NeoPixels.
Under view of the long NeoPixel string, now with wires to/from first and last NeoPixel
Photo by chebe
We now have many exposed solder joints involving thin wire. I want to insulate them (from body sweat, spills, etc), and provide some physical support. You can hot-glue them, but as I'm going to wear this I don't want to worry about body heat softening the glue. So I'm going to Sugru the backs. Little round balls of Sugru, pressed into the backs to make discs. Leave for two days to cure.
Under view of long NeoPixel string with white Sugru covering backs
Photo by chebe
I want to add more support, so I also add little crescents of Sugru to the points the wires meet the NeoPixel boards, from the front. Leave to cure for two days.
Under view of long NeoPixel string with black Sugru covering base of wires
Photo by chebe
Okay, the NeoPixel string is basically done. But we need it to be a grid. To help the NeoPixels keep the shape we want, and to help support the weight, I made a square, with a cross inside it, from cotton webbing/stay tape sewn together. But wait, how am I supposed to wear it? I want this to be removable, not permanently attached to any one garment. So I made sure to sew loops into the ends of each tape as attachment points.
Lining up two flexible things is awkward, but I found hair grips/bobby pins worked great to hold everything roughly in place while I hand sewed the wires to the tape. You want to make sure that it is the tape that is taut, not the wires, to reduce pulling.
Hair grips/bobby pins holding cotton tape frame to long NeoPixel string, back view
Photo by chebe
With the wires sewn to the tape, weave the long wires from the last NeoPixel through the other wires, along the outside edges of the grid, on the way back to the first NeoPixel.
Weaving long wires from last NeoPixel through other wires on way back to first NeoPixel, front view
Photo by chebe
Now it's an actual grid. But it needs to connect to a microcontroller. Best practice says to use a resistor (300-500 ohms) on the Data in line. So I added a tiny three-strip wide stripboard before the first NeoPixel. Make sure to break the board connection beneath the resistor. Then I soldered the Data line to connect with the resistor, both Ground wires into the one line, and both Powers into the other line. On the other side I soldered a three-pin connector (e.g. 3-pin JST). I then covered the stripboard with two layers of heat-shrink tubing.
Stripboard with resistor adding connector to NeoPixel grid
Photo by chebe
Okay, moment of truth, time to test. I used an Adafruit Flora, the basic strandtest example, and turned it on. Oooh, pretty.
NeoPixel grid, on, displaying rainbow pattern, laying flat
Photo by chebe
When I say silicone wire is flexible, I really mean it. It can bend and conform to surfaces with almost no memory. And any memory is easy to correct. Here is my grid wrapped around a plastic tube.
NeoPixel grid, on, displaying rainbow pattern, wrapped around a plastic tube
Photo by chebe
And here it is twisted around itself many times in the middle. (This is probably not the best photo, the strandtest example had moved on to the blinking rainbow section, those NeoPixels are intentionally off, not shorting.)
NeoPixel grid, on, displaying blinking rainbow pattern, with middle twisted
Photo by chebe
Here it is worn (under a semi-sheer top), off. You can see the lumps of the NeoPixels themselves, but nothing is constricted or compressed. The grid is conforming to my body, rather than the other way around.
NeoPixel grid worn, under semi-sheer black tshirt, off
Photo by chebe
And here is it worn, and on. Again you can see the grid conforming to my body rather than constricting it. You can also see that I only have it attached at the top two corners. The grid is so flexible that its own weight (91g) is pulling it down in the middle. (Easily corrected by attaching more points of the top tape to the outfit.)
NeoPixel grid worn, under semi-sheer black tshirt, on, displaying rainbow pattern
Photo by chebe
So it's flexible, it's versatile, but how durable is it? This is the first version, so we'll have to wait and see.
