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DLE (Globes of Fire) Part 5 – First Board!

When a new telescope is completed, one of the big milestones is known as “first light” – the first time that the telescope is used as it is intended.

Now that I am the proud owner of a reflow oven – a modified Black & Decker toaster oven fitted with Whizoo’s Controleo3 reflow oven kit – and I have a new version of my boards back – it’s time to think about how to build these things in a reasonable way.

The plan is obviously to switch from hand-soldering to reflow. To do that, the first thing that I need is a stencil that I can use to apply solder paste. Thankfully, kicad makes this really easy; you can modify the solder pad tolerances in the program, and the pcb editor can write out SVG files (thanks to Rheingold Heavy for this post). If I have the pads, I can easily cut a stencil, likely out of mylar because it’s a bit cheaper than Kapton is.

That would give me a way to do a single board if I could hand-align it closely enough. But each of the globes needs 12 of these boards, and hand-aligning is a pain.

So… what my real plan to do is to cut holes in a piece of hardboard (or cardboard) that will hold a number of the boards (12 or 24) and then a matching stencil. If I align the stencil one, then I can put solder paste on all of them.

IMG_9223

So, here’s the test. I took the pad svg and the board edge svg, joined them in inkscape and then cut them on the glowforge. As you can see, the boards fit perfectly into the cutouts, and the solder pads cut correctly. Next I will need to do a better version of this, with different colors for the pads and board edge so I can turn them off and off when laser cutting. I’m also probably going to cut holes for some posts that will give me registration between the board with cutouts and the stencil.

You can also see the first two boards that ran through the reflow oven. I did the solder paste without a stencil and I also skipped baking the LEDs since they showed up in a factory-sealed pack and have been sealed since, and both boards came out fine. And a 10 minute reflow cycle is a lot quicker than hand soldering…


Provisioning and using the ESP8266 controller

The ESP8266 controller is preprogrammed with the ability to connect to your local wifi network and be remotely controlled.

Provisioning

Initially, the controller does not know how to connect to your network, so it sets up its own network. Here is how to set it up:

  • Using your phone/laptop/tablet, connect to the network named something like “EDP_1002170403”. The password is the same as name of the node.
  • One you are connected, open up your browser and navigate to http://192.168.4.1. That should enter the provisioning page. Enter the SSID of your wireless network and the password, and click on connect.
  • If everything is working correctly, that will connect to your wireless network. You can find out the IP address by looking for the “EDP_…” name in your browser’s host table, or you can hook the esp board up to your computer and watch what it writes out the serial port when it boots.
  • Controlling via http

    You can control the LEDs via http by sending textual commands to controller. The format looks like this:

    http://[ip address]/message?content=[message]

    Controlling vs UDP

    If you want realtime control of the LEDs, http may have too much latency, which may result in unexpected pauses. The controller also supports communicating through UDP.

    To connect via UDP, use the same IP address and pass commands directly. The internal controller code runs at 100 Hz; if you drive with UDP messages at 60 Hz everything should just work great.

    Supported Messages

    All commands are three letters long, followed by another character (the examples use an underscore (“_”), followed by numeric parameters.

    The following commands are supported:

    Alternate

    Alternate between two colors.

    alt_r1,g1,b1,r2,g2,b2,time

    r1, g1, b1: the rgb values (0,255) for the first color (0-255)
    r2, b2, b2: the rgb values for the second color
    time: the time for each color

    Example: alt_0,100,000,000,000,000,250


    Blend to

    Blend from the current color to a specified color

    rgb_r,g,b,time

    r, g, b: the rgb values (0,255) for the new color
    time: the time for the blend

    Example: rgb_255,255,255,1000

    Color rotate

    Rotate through a bunch of different colors.

    col_speed,brightness

    speed: the speed of the rotate
    brightness: The brightness of the colors

    Example: col_5000,200

    Flash decay

    fdc_decay,min,max

    decay: the speed of the decay
    min: the minimum pause before the next flash
    max: the maximum pause before the next flash

    Example: fdcx250,10,500

    Full control

    Full control is used to control the color of all the leds directly.

    ind_chunk,data-bytes

    chunk: the number of leds to apply each set of data to.
    data-bytes: colors express as two digit HEX values in the format RRGGBB

    Example: ind_011,000044440000004400

    Each color in data-bytes will apply to 11 LEDs. The data-bytes contain 3 color values:

    000044 – a blue value
    440000 – a red value
    000044 – a green value

    Save

    Save the current animation so that it will use that animation when rebooting.

    s

    Set pixel count

    Set the number of pixels that the controller will use. This will result in a reboot of the controller.

    n_count

    count: the number of pixels

    Example: n_13



    DLE (Globes of Fire) Part 4

    It’s been very long since my last update, and a fair bit has happened.

    Hardware:

    I did a rev 1.2 of the board and sent them off to allpcb for a small run (10 IIRC, so 120 of the LED boards and 15 of the end boards).

    The boards showed up quickly, and didn’t work. Well, two of the LEDs worked sometimes, but the third would not.

    Clever me, I did some led moving and I managed to route the VCC line for LED #2 right across the data out pad when I did some moving. I could break the pad by hand and get them to work, which through trying to be quick led me creating a circuit that would work for all the colors except white because I didn’t break the trace completely. Which led me to think a new real of LEDs was bad and waste a couple of days trying to track down what was going on.

    I took the opportunity to do rev 1.3:

    image

    I bumped the VCC and ground tracks up in size, redid the VCC routing, and just generally cleaned things up to be nicer. I also added (finally) a 100 nF decoupling capacitor to the right of the #1 LED, which should help eliminate glitches in the future.

    I spun a small verification order (3) through OSHPark because it was only $5, and those worked great. After that, I pulled out my little list of material costs, went back to reprice the PCBs, and found that JLCPCB would do my full first order for $83 delivered, which was about 30% less than the $120 I had written down. Given the temporary nature of PCB special deals, I put that order in, and today found this on my doorstep:

    IMG_9215

    Well, technically they were in a *box* on my front porch. That is 600 of the LED facets in the two bags at the top and 50 of the top facet in the small box. And the two pretty purple boards are the test ones from OSHPark.

    Assembly

    I’ve gotten pretty good at soldering the LEDs on the facets, but my plan all along was to reflow them. Towards that, I picked up a few things:

    That’s a nice little Black & Decker TO1313SBD toaster oven.

    And:

    That’s a Controleo3 toaster oven conversion kit. We’re going to hot-rod that oven, adding a full computer control to it (the blue board on the left), add an extra heating element, a lot of insulation, and even a servo to open the door.

    All of this will give me a reflow oven; you can put a board with solder paste and components on it, hit a button, and it will heat the board at a certain rate until the solder melts and then cool them down at an appropriate rate. It’s going to live under the garage near the laser cutter, and my guess is that I’m going to need a bit of ventilation for it.

    Firmware

    I am at what I think is the V1 firmware, for approximately the third time. This took a whole lot of time and effort, with the usual fun of running two different codebases on two microcontrollers connected over USB.

    Provisioning

    The first time setup for IoT devices can be a bit of a pain, as they have to get your wireless ssid and password. In playing around, I found that iOS doesn’t let you enumerate wireless networks or change connections programmatically, which meant it might be a real pain to set up multiple nodes by hand.

    Then, I had a small bit of insight, and realized that I already had a device that could easily enumerate all the wireless networks; the ESP can do that an I already had the code because I needed it for testing. It was merely a matter of grafting it onto the existing code.If you connect to the network for any node and give it an SSID and password, it will verify that it works and then pass it off to all of the other nodes so that they can auto-configure. That code is all done, and it’s pretty cool to watch because the current firmware shows the state of the connection by flashing. Okay, maybe that’s only a little cool.

    Animation

    I wrote a few of the simple animations that I want; some color rotations, a flash and decay animation, and a blend from the current color to a new one.

    I also wanted to be able to go fully to the metal and control every LED remotely and quickly. That led me to a better Http server for the ESP, a brief flirtation with TCP, and finally an implementation based on UDP. The server is fast enough that you could send the data for all 33 leds 500 times a second and it would work; it is currently constrained to 100 Hz because that is the speed the animation loop runs at, and I expect that for real applications sending data at 60 Hz would be fine.

    I am particularly happy with how the command processor worked out; the implementation is nice and clean.

    The wireless information is stored in permanent memory, and it is also possible to store the current animation so that it will resume on startup.

    Software (app)

    I want to have an app to control all of this. It needs to support both Android and iOS, which made Xamarin the logical choice; I can support both and I can write C# code which is a huge plus in my book.

    Like many open-sourcy software, it can be a real pain at times, but I’m able to build an app that deploys to my phone and debugs, and that’s a decent first step. I’m working on network discovery right now; once the provisioning is done, the app needs to enumerate all local ip addresses and see if one of my controllers is hiding there.

    And I’m using Xamarin Forms, which is built on top of XAML, which I guess is an advantage since I did XAML professional for a fair bit, but it’s a bit of a mind-bender as usual.

    I wanted to do something different for discovery, so I wrote a graphical pinger. Here’s a video.

    The app still needs a lot of work; it needs a way to do the initial provisioning, a way to list the different animations it can do, a color picker, etc.


    DLE (Globes of Fire) Part 3

     The new boards arrived from allpcb.com. To recap, this, time I went with standard 0.1” (2.54mm”) header pins between the boards. I ordered some angled headers from the Amazon to use for the connections.

    IMG_9061

    After I populated 11 faces with LEDs, it was time for assembly. Here’s the first approach:

    IMG_9063

    The first concept was to wire the faces together with short pieces of header on the back. This worked poorly; it took a long time to hook them up and the angles were rarely right. The first half was technically done, but I was unhappy.

    For the second half – and keeping in mind that prettiness was not a requirement – I decided to go with another approach. I would use angled headers on the outside, and just solder the pins together where they overlapped.

    But first, I needed a better way to set the angle. The led to the following design in TinkerCAD:

    image

    And then a long session of setup to migrate my 3D printer from an absolutely ancient laptop to one that was merely old. I printed up a whole set of these, and then used them to hold the faces at the right angle for soldering. That resulted in this upper ring:

    IMG_9068

    The alignment clips on the right worked very well; it only took about 30 minutes to do this whole ring. And yes, it’s very ugly.

    Time to hook them together, and then attach on the end face. These are attached with small pieces of header pin on the outside.

    IMG_9069

    Then it’s time to wire up the 5 volts, ground, and data, and take it out for a spin.

    The first attempt was not successful; one ring lit and the other didn’t. A quick check discovered that the ground connection between the two rings was not functioning, so I added an additional connection. Which led to this:

    IMG_9071

    The driver is running some simple rainbow code, so each LED is a slightly different color.

    Finally, adding on the requisite acrylic globe gives us the following:

    Globe of fire from Eric Gunnerson on Vimeo.

    Overall, I’m mostly happy. It would be nice if the header holes were a bit tighter on the pins, and I could clearly get by with 2mm or even 1.27mm pins. The 3d-printed alignment clips could use another iteration to make them easier to use.



    DLE (Globes of Fire) Pt 2

    A week or so goes by, and I get a package back from allpcb, so I started building one.

    Each half has a ring of 5 pentagons plus one the end, so I started hooking 5 boards together:

    IMG_9044

    The WS2812 LEDs are only 5mm on a side, so the whole board is roughly 15mm x 17mm. That’s tiny, and frankly working on it was a huge pain. I did this, put the boards into a box, and closed it.

    Then I came back the next day and decided to have another try. Rather than connect on the outside, I decided to use a much lighter wire and connect on the inside (back) of the boards. Here’s a set of 5 with VCC and GND hooked up:

    IMG_9046

    Yes, that’s some *ugly* soldering, but in my defense I’d like to note that the spacing on the holes is about 0.05”/1.3mm. This then gets folded into a ring. Eventually, we end up with the top and bottom:

    IMG_9050

    Next, those two are soldered together with wires to carry VCC and GND between halves, and you end up with this:

    IMG_9052

    Next was to wire through the data ports. Basically, it starts at one face at the open end, goes around that ring, goes around the lower ring, and finally travels to the bottom. Add in some hot glue to help hold things together, and put the LEDs on, and here’s the result:

    IMG_9053

    That is one ugly bit of construction, and it took a lot longer than I had hoped.

    IMG_9055

    After soldering a few hundred WS2812s, you learn how to do it without burning them up. On the left is one face from the 3-LED version that I tested to verify the layout.

    V1.1

    The first version was technically a success, but only because I so cussedly kept on. I was wondering if I could make something small enough to fit in an ornament ball, and the answer is “yes”, but you really don’t want to do it.

    So, it’s practically a failure.

    The biggest problem is the connection between the faces; the holes are too hard to solder, and using individually-cut wires is a pain…

    So, I’m going to abandon the single-LED version (kindof – more on that later) and work on the 3-LED version. I started by going with standard 0.1” (2.54mm) header spacing, and the plan is to use angled headers. The angled headers will stick out to the side, and two faces are connected by soldering the ends of the header pins together. It’s going to look a big weird, but should be a lot easier to construct.

    Here’s the old design and the new one:

    image

    Obviously, the big different is the connectors; they are much larger, though the overall design is only a big bigger. I’ve used the extra space to pull the LEDs a bit farther apart because trying to hand-solder the LEDs in the first version was a difficult. And I added a little bypass jumper; if you solder a wire (or better, a 0805 zero-ohm resistor) across those pads, you can omit the bottom two LEDs and things will work fine.

    If you read backwards, you might see that it says “Dodecahedral Light Engine” on the back, which is the new name for the boards.

    A fully-populated DLE will features 33 LEDs, pull 2 amps @ 5V with everything on white, and put out quite a bit of light.

    I need one more design review pass before I send this one out to have boards made.





    Globes of Fire!

    The parts for the new controller have started trickling in, but until they all show up I’m a stuck there, so I’ve been thinking in other areas.

    In the olden days – pre LED – I had a number of the 50 or 100 light globes in my display:

    See the source image

    I liked them for their intense burst of light, but the ones I had gradually died, and I haven’t found a replacement.

    So… I got thinking again about options. When I built my Animated Snowman, I used WS2182 leds on the faces of 3d-printed dodecahedra. It worked fine, but the hand-cabling was a pain:

    IMG_8435[1]

    Using the acrylic lamp globes worked great, however. They are cheap, easy to get, and fully waterproof. I just needed a better way to get the LEDs in place.

    One of the nice things about dodecahedra is that the faces are all pentagons. I remember a hack-a-day article a couple of years ago when somebody built one by soldering pc boards together, so I decided to do a design of that what that might look like:

    image

    The concept is that any face can hook to any face. You wire up the ground and VCC connections on all faces to give rigidity to the dodecahedron, and then wire up the DIN and DOUT connections from face to face in whatever pattern makes sense.

    This design gives me 12 LEDs (well probably 11, since the top or bottom one will be used for support) in the space of about an inch, so that would easily work in the small acrylic balls (6”, or 4” if I can get them).

    Of course, why do one LED per face when you can do 3:

    image

    Same concept as before; hook up DIN from another face, it will chain through all three LEDs and then head out through DOUT.

    This board is roughly an inch in size, so the resulting dodecahedron will be around 2” in size. That will give us 33 LEDs and live up to the title of the post, but it may be overkill, which is why I’m going two versions. I’ll drill a hole through the 12th face and use a threaded rod and nuts to mount the DLE (Dodecahedral Light Engine).

    I need to do some design cleanup and then send off for a run of these to see how they work.


    Snowflake–custom controller

    The Adafruit Huzzah was a nice starting point for the snowflake, but it’s both more expensive and not well-tuned for what I need. To drive the WS2812s, all I need is a single output, and I don’t need dedicated buttons on the board.

    I went back and forth on whether I wanted to do two controller boards – one that used the ESP8266 and another that used a cheaper AVR, but the ESP can be had so cheaply that it hardly seemed worth it. I considered a number of different ESP modules – or even building directly from the ESP8266 and adding flash, but the ESP-12 is pretty cheap and it has FCC certification (or is claimed to, at least).

    So, basically, I took the Huzzah design and looked at it in Eagle, and then pared off things that I didn’t need and did my design in KiCad. It currently lives here.

    The design is pretty minimal; it has a small 3.3 volt linear regulator to power the ESP (I used the same SPX3819 as on the Huzzah), appropriate resistors to put the ESP in the right state, diodes to handle level conversion between the 5V world and the 3.3V world and two headers. There’s a 6-pin programming header that has power, serial connections, and the reset and GPI00 pins on it, and there’s a three pin header for operation that has 5V and GND in to power the board and the data line out for the WS2812 string. Simple and straightforward. There will probably be another version with another sensor; I’m going to need a way to reset these things to handle wireless setup and my new design will be fully encapsulated, so I’ll probably do something magnetic.

    Here’s the schematic:

    image

    Once I had that, it was off to do the PC board layout. That is really my favorite part of the process; to go from a set of random components on the board to something functional (and perhaps even elegant) is a rewarding process. Here’s the layout.

    image

    I decided that I wanted both sets of connectors at the bottom and the ESP-12 at the top. Basically, the jacks are at the bottom, the 3.3V supply is in the middle, and the resistors, diodes, and LEDs are on the sides. All of the small components are 0805 sized, since I wanted something that I could hand-solder if necessary, and those will also reflow reasonably well if I want. Given the need for two jacks and the space they take up, there’s not a lot of margin in going smaller at this point.

    One of these times, I’m going to do snapshots of what it took to get to a decent layout.

    The PC boards got finished and sent out to AllPcb.com, who sent me 10 (actually, 11) copies of the board for a total of $5.49 with about a 7 day turnaround. I don’t understand the economics of how that can be profitable, but I’m not going to complain right now.

    Initial guesses at the overall costs for the controller:




    Part Price
    ESP-12 Module $1.78
    3819 regulator $0.06
    Other parts $0.11
    PC board $0.50
    Total $2.45

    No labor in there yet, but it’s just a matter of putting the parts on there and reflowing them. It should be pretty quick, and I’ll check to see what it would cost to outsource it as well.

    The boards have showed up, but I was too cheap to pay for fast shipping of the other components, so they’ll trickle in and then we’ll see if my design works.



    Snowball pricing analysis

    I’ve been thinking about maybe selling the snowflakes – or a variant of the snowflakes – commercially. Pursuant to that, I did a few calculations on parts costs.

    Here’s what it would take to build the prototype in volume (say, 100 units):



    Part Price
    PC Boards $2.04
    55 WS2812 LEDs $3.72
    Adafruit Huzzah $7.96
    Acrylic $4.07
    Printed separators $1.00
    Labor @$13/hour $26
    Total $44.79

    The labor is frankly a bit of a guess; it’s probably quite a bit worse than that.

    Assuming I wanted a 50% margin, that would put the retail cost at about $90. The snowflakes are nice, but I’m not sure they are $90 nice.

    To reduce the price, we need to look at the places that are the most expensive. Clearly, labor is a problem, so making the design easier and more robust to assemble is going to be critical. And the cost of the Huzzah is a big part of the parts cost, so coming up with an alternative that is easier and cheaper to use makes sense.



    Snowflake Final

    The snowflakes – five in total – have all been finished.

    Well, mostly finished… there are three animating themselves on the gutters of the house right now, while the remaining two (which were on the house until this afternoon) are waiting for their waterproofing to cure.

    This post will cover a lot of ground, since I missed a couple of updates along the way. 

    Assembly

    When we last left our story, we had a PCB in the snowflake form and some laser-cut pieces of translucent acrylic that go on the front.

    The next step was to put the LEDs on the board. My hope had been that I could use the hot air rework station to reflow all the LEDs, but a bit of experimentation showed that I was melting the LED cases and hand soldering was faster, so I went that way. I think a cheap reflow oven is in my future.

    I used the following approach:

    1. Add solder to all the solder pads on the snowflake (55 * 4 = 220 of them).
    2. Carefully hold an LED in the right position, and touch two of the pads to tack it in place.
    3. Press down hard on that end of the LED, and touch each pad until the LED sinks down even with the level of the board at that end. .
    4. Repeat on the pads at the other end of the LED.
    5. Reheat the first two pads to get rid of the stresses induced when the second end was dropped down.

    That was mostly straightforward, except it turns out that if you put the LEDs in backwards, they turn into HEDs – Heat Emitting Diodes – and you get to remove them and put new ones in their place. I put my new hot air rework station – a 9570W+ – to work at that.

    Eventually, I got all of them soldered correctly, fixed some connection issues between the boards, and had something I could run my initial animation code on.

    It worked.

    My original plan was glue the PCBs directly to the acrylic, but I discovered that I liked the result better if there was some space between them. I did tests using pennies as spacers, grabbed my calipers to get some measurements and drew a quick drawing, and then came up with this in TinkerCad:

    image

    And then printed up a bunch of them in clear PLA. They mostly work pretty well; the only downside is that the connection at the small end needs to be flexible to warp around the board but that also makes it a bit weak, so I’ve broken a few of them. Carefully put them on the PC board and squeeze in the acrylic, and you end up with this:

    image

    Call this the first prototype. At this point, I was a bit tired of soldering and was waiting for some more parts to show up – and finding out that Amazon’s two-day prime shipping is only aspirational at times – so it was time to write some code.

    Code

    Both the code and the circuit designs live in GitHub here.

    I’ve written four or five versions of color-blending animation code. Last year I wrote a nice abstraction that worked great for the linear strip animations I was doing, but it didn’t adapt very well to what I wanted to do here, so I went back to first principles.

    Using polar coordinates, the code knows the location of each LED on the snowflake. For some of the animations, the color is determined by either the angle or distance of the LED from the center, and in these, there is just a simple mapping that says “add the animation offset to that number, and then use it to find a color”.

    The nice part of this approach is that is gives me appropriate color blending across the whole snowflake.

    I spend a few days on the code, and it’s decent as a first try. It implements four animations:

    • A continuous rotation of all the colors around the arms of the snowflake.
    • An animation of colors based on the distance of the LEDs from the middle.
    • A “sparkle” effect; all the LEDs smoothly and slowly blend between colors, while random LEDs flash full white and then fade back to the current color. I wrote some nice code for this.
    • A bouncing effect called “worm” that is a bit of a take on the Larson Scanner, but across opposite arms of the snowflake, also with color blending.

    I had more ideas for animations, but decided to freeze the implementation so I could finish the build.

    Autonomous display

    For the prototype so far, I was driving it with a ESP that was powered by the serial port, and with a short ribbon cable carrying signals to the snowflake itself.

    My plan was to put the ESP remote from the snowflake (so it could be under the eaves and shielded from rain), so I cut two-foot lengths of red/black/yellow wire (for power and signal), wired everything up, plugged it in…

    And the LEDs started flashing randomly. Tried decoupling capacitors, tried signal resistors, tried a whole bunch of things, and nothing worked; if I made the signal line longer than about 10”, it wouldn’t work.

    Trying to fix that consumed the better part of a day. Ultimately, I decided that the problem was that I was getting a lot of transients, so I decided to run the 5V power directly to the snowflake, and then chain the ESP off of that.

    And it worked perfectly the first time, leading to this arrangement:

    image

    Plus 4 = 5

    During the long hours of making four more of the PCBs – cursing my choice to use tiny pads for data connections and not doubling them – I realized that there was a far better way to do the attachment; if I allowed the boards to overlap vertically, I could use through-holes that aligned between the parts and just solder component leads into the holes. My guess is that I could do that basic board in about 1/10th the time, even less than that if I could reflow solder the LEDs. And the boards can probably be (mostly) square, which will make them easily fababble, easily broken apart, and they will fit tighter for better utilization.

    Sounds like version 2 to me.

    I didn’t take any pictures during this time, but it was a huge pain in the butt to get them all working; the tiny data paths were especially troublesome.

    Finally that, was done, and I could turn to other matters. Four more Huzzahs were wired up:

    image

    and were all attached to the snowflakes.

    With the Huzzah mounted close, it needed some protection, so a bit more time in TinkerCAD yielded a nice little case:

    image

    That’s a PrintrBot simple metal pro with a custom heated bed on it. I had the usual problem getting tolerances right, but eventually got to here:

    image

    Power

    Whenever anybody asks me what the hardest part of these projects is, I always respond “cabling”.

    LEDs are power hungry, and unfortunately small wires introduce voltage loss, which means you get color shift. If I had 3 snowflakes on one wire, the last one is going to be dimmer and the colors will likely shift as well. In my previous projects I’ve resorted to powering strips at both ends and using thick landscape lighting wire, but it’s a huge pain.

    This time, I got smart.

    WS2812s pull about 60 mA max if they are all white, and with 55 of them I needed 3.3 amps @ 5 volts. Since I can live without full white, I decided that 3 amps would be sufficient. And bought 5 of these:

    image

    One of these will be right next to each snowflake, and then I just need wires that supply something around 12 volts, and everybody will get a nice solid 5V supply and be happy. I reused the 10-gauge wire I had for the project this replaced, but I could easily get by with something like 18 gauge.

    I’m not sure powering with DC is the right approach, however; it might be cheaper to go with small 5V AC power supplies and just use standard AC cords.

    Waterproofing

    I live in the Seattle area, and the holiday season is generally quite wet, and the electronics will need some protection from the elements.

    I have quite a bit of West Systems epoxy sitting in the garage leftover from a custom subwoofer enclosure I did a while back, but their website didn’t yield much information about its conductivity. So, I built this:

    image

    and embedded it in a whole lot of epoxy:

    image

    image

    Works fine…

    Distractions

    About this time, I had a couple of distractions. First off, this showed up from Italy:

    IMG_8960

    Getting it picked up, legs on it, and ordering parts to recondition it took a bit of time.

    And, I had an event where I needed the snowflakes to be part of the display, so I totally finished two of the snowflakes and put them out on the house, trusting that the weather would stay unseasonably dry. Here’s the bench test:

    image

    You can see the DC->DC converter to the left of the lower snowflake.

    I should at this point mention that pictures or video never do these colors justice; they are much more intense than they show up here.

    Waterproofing part 2

    To keep the attached wires in the right spots, the wires and the Huzzah needed to be supported above the PCB which will be covered in epoxy. Here’s what I ended up with:

    image

    After I carefully poured epoxy over all the parts of the board that needed them, the boards got hung up to cure:

    image

    It being about 40 degrees in the garage, they did not cure overnight and eventually I had to pull them inside to finish curing. They looked like this when they finished curing:

    image

    I retested them. One of them worked perfectly, the other two did not; only some of the LEDs worked.

    So, out came the air rework gun to debond the epoxy in an area and then I could trace from there. I ended up replacing about 5 LEDs; from what I can tell they were touching but no soldered, and the cold weather shrunk things enough so that the epoxy could get in there. I also had one pcb trace break (really?). Then, those two got an epoxy touchup to cover over the reworked areas. .

    Finally, the huzzah box got hot-glued to the back and silicone was used to plug the hole.

    Not perfect, but version 1.

    image

    You can also see the molex connectors that bring 5V into the snowflake.

    Videos:



    Snowflake from Eric Gunnerson on Vimeo.



    Version 2

    *Lots* of ideas for version two, which might be a commercial version.

    • The whole mounting and waterproofing approach is far too finicky and may not work very well. I’m considering vacuum-forming the snowflake out of thinner plastic with both a front and back, and those can then be solvent welded (or siliconed) together to give me something that is truly waterproof. It will also give much better support for the PC boards.

    • The approach of “click-together” pc boards worked, but it required fine-tuning for each and every joint and then detailed soldering for each part. And then rework when the stresses built up. Instead of click-together, I’m going to use overlapping boards that are connected with through-hole wiring. That will take me down to 10 easy-to-solder joints per arm, or about 60 in total. I also think I can get each of the PCs to be rectangular in format, and that will make panelization easier and waste less space. I think.
    • I really need a way to reflow solder all the LEDs, and it may be time to make/buy a tiny reflow oven. Or *maybe* get somebody to do that for me, though the initial quotes I looked at are higher than I expected.
    • Moving the ESP8266 onto the snowflake board, probably on the back. That would require adding a simple 3.3V regulator for power and (probably) programming pins. I’m currently using an ESP-12; I could probably get away with a simpler one but they are pretty cheap already so it may not be worth it.
    • Add more built-in animations. Color wipes in the x/y direction, flash and off animations, concentric rotating color blends could all be done.
    • WiFi coordination between standalone snowflakes, with a dedicated network just for the snowflakes, and *maybe* a separate gateway to connect to an existing wireless network.
    • WiFi connection to an existing wireless network to allow control of the snowflakes. This might encompass setting their default set of animations, being able to download new animations, or being able to do “command control” over the wireless network, either just setting the animation that’s being run or driving every LED independently.


    Snowflake update…

    Have made decent progress on the snowflake. I have two PCBs assembled and populated. The right way to do it would be to use a reflow oven, but I’ve settled on using my new hot air rework station and solder paste to do the data lines – since the pads that I need to connect are tiny – and hand soldering everything else, including the LEDs. I did reflow on a test LED and it worked, but I had to get things hotter than I would like.

    I finished the outline design and cut the snowflake fronts from white acrylic. This was a bit frustrating; the Glowforge is advertised as being able to cut about 11.5″ in the forward/back direction, but they haven’t been able to achieve that, so I had to cut slightly smaller than I wanted.

    I used one sheet each of #7328 and #2447 acrylic so I could see which one I liked better:

    IMG_8876

    After playing around a bunch (something like 15 variants) with both plastics and with keeping them different distances from the LEDs, we settled on 2447 spaced about 10mm away.

    Then it was off to Tinkercad to design a clip that would hold the front to the pc boards, which finally led to this. You can see the clips (printed in clear PLA) holding the snowflake at the right distance.

    MVI_8888 from Eric Gunnerson on Vimeo.

    After a false start or two, I think I have a handle on how I want to structure the animation code; it’s nice and mathy…

    Now I just need to order some more Huzzahs to drive the other snowflakes, figure out how I’m going to handle the cabling, and buy some waterproof 12V –> 5V buck converters (I’m tired of worrying about voltage drop).

    The video is powering the LEDs from a USB port using tiny wires, and the 5V supply is sagging down to around 4 volts because of the load. So, it will be brighter than this.


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