diff options
Diffstat (limited to 'posts/wifi-led-driver')
| -rw-r--r-- | posts/wifi-led-driver/images/board_in_case.jpg | bin | 2898747 -> 0 bytes | |||
| -rw-r--r-- | posts/wifi-led-driver/images/board_in_case.small.jpg | bin | 817789 -> 0 bytes | |||
| -rw-r--r-- | posts/wifi-led-driver/images/boards.jpg | bin | 3642485 -> 0 bytes | |||
| -rw-r--r-- | posts/wifi-led-driver/images/boards.small.jpg | bin | 865465 -> 0 bytes | |||
| -rw-r--r-- | posts/wifi-led-driver/images/layout.png | bin | 114048 -> 0 bytes | |||
| -rw-r--r-- | posts/wifi-led-driver/images/schematic.png | bin | 301982 -> 0 bytes | |||
| -rw-r--r-- | posts/wifi-led-driver/index.html | 183 | ||||
| -rw-r--r-- | posts/wifi-led-driver/resource/lyza_schematic_and_pcb.pdf | bin | 781457 -> 0 bytes |
8 files changed, 0 insertions, 183 deletions
diff --git a/posts/wifi-led-driver/images/board_in_case.jpg b/posts/wifi-led-driver/images/board_in_case.jpg Binary files differdeleted file mode 100644 index 843900a..0000000 --- a/posts/wifi-led-driver/images/board_in_case.jpg +++ /dev/null diff --git a/posts/wifi-led-driver/images/board_in_case.small.jpg b/posts/wifi-led-driver/images/board_in_case.small.jpg Binary files differdeleted file mode 100644 index 5c0aa81..0000000 --- a/posts/wifi-led-driver/images/board_in_case.small.jpg +++ /dev/null diff --git a/posts/wifi-led-driver/images/boards.jpg b/posts/wifi-led-driver/images/boards.jpg Binary files differdeleted file mode 100644 index 79f8154..0000000 --- a/posts/wifi-led-driver/images/boards.jpg +++ /dev/null diff --git a/posts/wifi-led-driver/images/boards.small.jpg b/posts/wifi-led-driver/images/boards.small.jpg Binary files differdeleted file mode 100644 index 6f5c28c..0000000 --- a/posts/wifi-led-driver/images/boards.small.jpg +++ /dev/null diff --git a/posts/wifi-led-driver/images/layout.png b/posts/wifi-led-driver/images/layout.png Binary files differdeleted file mode 100644 index 11fc50e..0000000 --- a/posts/wifi-led-driver/images/layout.png +++ /dev/null diff --git a/posts/wifi-led-driver/images/schematic.png b/posts/wifi-led-driver/images/schematic.png Binary files differdeleted file mode 100644 index 8294f12..0000000 --- a/posts/wifi-led-driver/images/schematic.png +++ /dev/null diff --git a/posts/wifi-led-driver/index.html b/posts/wifi-led-driver/index.html deleted file mode 100644 index c7b8053..0000000 --- a/posts/wifi-led-driver/index.html +++ /dev/null @@ -1,183 +0,0 @@ -<!DOCTYPE html> -<html lang="en-us"> - <head> - <meta charset="utf-8"> - <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>Wifi Led Driver | blog.jaseg.de</title> - <link rel="stylesheet" href="/css/style.css" /> - <link rel="stylesheet" href="/css/fonts.css" /> - - <header> - <nav> - <ul> - - - <li class="pull-left "> - <a href="https://blog.jaseg.de/">/home/blog.jaseg.de</a> - </li> - - - - - </ul> - </nav> -</header> - - </head> - - <body> - <br/> - -<div class="article-meta"> -<h1><span class="title">Wifi Led Driver</span></h1> - -<h2 class="date">2018/05/02</h2> -<p class="terms"> - - - - - -</p> -</div> - - - -<main> -<div class="document"> - - -<div class="section" id="project-motivation"> -<h2>Project motivation</h2> -<!-- FIXME finished project picture with LED tape --> -<figure> - <img src="images/board_in_case.small.jpg"> - <figcaption>The completed driver board installed in the 3D-printed case. This device can now be connected to - 12V and two segments of LED tape that can then be controlled trough Wifi. The ESP8266 module goes on the pin - header on the left and was removed for this picture. - </figcaption> -</figure><p>After the <a class="reference external" href="https://blog.jaseg.de/posts/multichannel-led-driver/">multichannel LED driver</a> was completed, I was just getting used to controlling LEDs at 14-bit resolution. -I liked the board we designed in this project, but at 32 channels it was a bit large for most use cases. Sometimes I -just want to pop a piece of LED tape or two somewhere, but I don't need a full 32 channels of control. I ended up -thinking that a smaller version of the 32-channel driver that didn't require a separate control computer would be -handy. So I sat down and designed a variant of the design with only 8 channels instead of 32 and an on-board <a class="reference external" href="https://en.wikipedia.org/wiki/ESP8266">ESP8266</a> -module instead of the <a class="reference external" href="https://en.wikipedia.org/wiki/RS-485">RS485</a> transceiver for WiFi connectivity.</p> -</div> -<div class="section" id="the-electronics"> -<h2>The Electronics</h2> -<p>The schematic was mostly copy-pasted from the 32-channel design. The PCB was designed from scratch. This time, I went -for a 5x7cm form factor to allow for enough room for all connectors and to give the <a class="reference external" href="https://en.wikipedia.org/wiki/ESP8266">ESP8266</a>'s WiFi antenna enough -space. The board has two 5-pin <a class="reference external" href="https://www.phoenixcontact.com/online/portal/de?uri=pxc-oc-itemdetail:pid=1757019&library=dede&tab=1">Phoenix-style</a> for two RGB-White (RGBW) tapes and one 2-pin <a class="reference external" href="https://www.phoenixcontact.com/online/portal/de?uri=pxc-oc-itemdetail:pid=1757019&library=dede&tab=1">Phoenix-style</a> connector for -12V power input. The control circuitry and the serial protocol are unchanged, but the <a class="reference external" href="http://www.st.com/resource/en/datasheet/stm32f030f4.pdf">STM32</a> now talks to an <a class="reference external" href="http://www.watterott.com/de/ESP8266-WiFi-Serial-Transceiver-Modul">ESP-01</a> -module running custom firmware.</p> -<p>The LEDs are driven using a <a class="reference external" href="http://www.ti.com/lit/ds/symlink/sn74hc595.pdf">74HC595</a> shift register controlling a bunch of <a class="reference external" href="http://aosmd.com/pdfs/datasheet/AO3400.pdf">AO3400</a> <a class="reference external" href="https://en.wikipedia.org/wiki/MOSFET">MOSFETs</a>, with resistors in front of -the <a class="reference external" href="https://en.wikipedia.org/wiki/MOSFET">MOSFETs</a>' gates to slow down the transitions a bit to reduce brighntess nonlinearities and <a class="reference external" href="https://en.wikipedia.org/wiki/Electromagnetic_interference">EMI</a> resulting from -ringing of the LED tape's wiring inductance.</p> -<p>The board has two spots for either <a class="reference external" href="https://en.wikipedia.org/wiki/Resettable_fuse">self-resettable fuses (polyfuses)</a> or regular melting-wire <a class="reference external" href="https://en.wikipedia.org/wiki/Fuse_(electrical)">fuses</a> in -a small <a class="reference external" href="https://en.wikipedia.org/wiki/Surface-mount_technology">SMD</a> package, one for each RGBW output. For low currents the self-resettable fuses should be okay but at higher -currents their <a class="reference external" href="http://m.littelfuse.com/~/media/electronics/datasheets/resettable_ptcs/littelfuse_ptc_16r_datasheet.pdf.pdf">trip times get long enough that they become unlikely to trip in time to save anything</a>, so plain old non-resettable fuses would be the way to go there.</p> -<!-- FIXME finished board photos --> -<!-- FIXME board with test tape picture --> -<figure> - <figure class="side-by-side"> - <img src="images/schematic.png"> - <figcaption> - The schematic of the driver board, with the ESP8266 on the top left, the STM32 microcontroller for LED - modulation below, the shift register in the middle and the LED drivers and outputs on the right. - <a href="resource/schematic_and_pcb.pdf">Download PDF</a> - </figcaption> - </figure><figure class="side-by-side"> - <img src="images/layout.png"> - <figcaption> - The board layout with the top side being visible. The top side contains the footprint for the ESP8266, the - microcontroller, fuses, filter cap, connectors and the shift register. The LEDs are connected on the left, - with one connector per LED tape segment. The power input connector is on the bottom right. The LED driver - MOSFETs are in small SOT-23 packages on the back of the board. Since this board is not intended for - super-high currents, the MOSFETs are adequately cooled just through the board's copper planes. - <a href="resource/schematic_and_pcb.pdf">Download PDF</a> - </figcaption> - </figure> -</figure><figure> - <img src="images/boards.small.jpg"> - <figcaption>The completed PCBs of this project (front) and the `multichannel LED driver`_ project the driver - circuitry was derived from (back). - </figcaption> -</figure></div> -<div class="section" id="the-firmware"> -<h2>The Firmware</h2> -<p>The <a class="reference external" href="http://www.st.com/resource/en/datasheet/stm32f030f4.pdf">STM32</a> firmware only had to be slightly modified to accomodate the reduced channel count since the protocol remains -unchanged. The ESP firmware is based on <a class="reference external" href="https://github.com/Spritetm/esphttpd">esphttpd</a> by <a class="reference external" href="http://spritesmods.com/">Spritetm</a>. The modifications to the webserver firmware are pretty -basic. First, the UART console has been disabled since I use the UART to talk to the STM32. The few bootloader messages -popping out the UART on boot are not an issue, since they're unlikely to contain the fixed 32-bit address prefix the -serial protocol requires for the <a class="reference external" href="http://www.st.com/resource/en/datasheet/stm32f030f4.pdf">STM32</a> to do anything.</p> -<p>Second, I added LED control by adding drivers for the serial protocol and a bunch of colorspace conversion functions. -When I first tested the prototype software, I noticed that color reproduction was extremely poor. When I just sent a -<a class="reference external" href="https://en.wikipedia.org/wiki/HSL_and_HSV">HSV</a> rainbow fade from a python command line, the result looked totally wrong. The fade did not seem to go at a constant -speed and some colors, in particular yellow, orange and greens, were not visible at all. The problem turned out to be a -stark mismatch of the red, green and blue channels of the LED tape and less-than-optimal color reproduction of the pure -colors. I decided to properly measure the LED tape's color reproduction so I could compensate for it in software. This -turned out to be an extremely interesting project, the details of which you can read in my <a class="reference external" href="https://blog.jaseg.de/posts/led-characterization/">LED characterization</a> -article.</p> -<p>Third, I updated the built-in websites with some ad-hoc documentation on how to use the thing and a basic interface for -LED control.</p> -<!-- FIXME screenshot of firmware website --> -</div> -<div class="section" id="making-an-enclosure"> -<h2>Making an enclosure</h2> -<p>To be actually useful, the driver needed a robust enclosure. Bare PCBs are nice for prototyping, but for actually -putting the thing anywhere it needs a case to protect it against random destruction.</p> -<p>The board has four mounting holes with comfortable spacing in its corners to allow easy mounting inside a 3D-printed -case. The case itself is described in an <a class="reference external" href="http://www.openscad.org/">OpenSCAD</a> script. To make it look a little nicer, a little 3D relief is laid -into the lid. The 3D relief is generated with a bit of blender magic. The source <a class="reference external" href="https://en.wikipedia.org/wiki/STL_(file_format)">STL</a> model is loaded into blender, then -blender's amazingly flexible rendering system is used to export a depth map of a projection of the model as a <a class="reference external" href="https://en.wikipedia.org/wiki/Portable_Network_Graphics">PNG</a> file. -This depth map is then imported as a triangle mesh into <a class="reference external" href="http://www.openscad.org/">OpenSCAD</a>.</p> -<p>For the relief to look good, I chose a rather high resolution for the depth map. This unfortunately leads to extreme -memory use and processing time on the part of <a class="reference external" href="http://www.openscad.org/">OpenSCAD</a>, but since I have access to a sufficiently fast machine that is -not a problem. Just be careful if you try opening the <a class="reference external" href="http://www.openscad.org/">OpenSCAD</a> file on your machine, <a class="reference external" href="http://www.openscad.org/">OpenSCAD</a> will probably crash -unless you're on a beefy machine or interrupt it when it starts auto-rendering the file.</p> -<p>The board is mounted into the enclosure using knurled insert nuts that are pressed into a 3D-printed hole using a bit of -violence.</p> -</div> -</div> -</main> - - <footer> - -<script> -(function() { - function center_el(tagName) { - var tags = document.getElementsByTagName(tagName), i, tag; - for (i = 0; i < tags.length; i++) { - tag = tags[i]; - var parent = tag.parentElement; - - if (parent.childNodes.length === 1) { - - if (parent.nodeName === 'A') { - parent = parent.parentElement; - if (parent.childNodes.length != 1) continue; - } - if (parent.nodeName === 'P') parent.style.textAlign = 'center'; - } - } - } - var tagNames = ['img', 'embed', 'object']; - for (var i = 0; i < tagNames.length; i++) { - center_el(tagNames[i]); - } -})(); -</script> - - - <div id="license-info"> - ©2020 by Jan Götte. This work is licensed under - <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/">CC-BY-NC-SA 4.0</a>. - </div> - <div id="imprint-info"> - <a href="/imprint">Impressum und Haftungsausschluss und Datenschutzerklärung</a>.<br/> - <a href="/about">About this blog</a>. - </div> - </footer> - </body> -</html> - diff --git a/posts/wifi-led-driver/resource/lyza_schematic_and_pcb.pdf b/posts/wifi-led-driver/resource/lyza_schematic_and_pcb.pdf Binary files differdeleted file mode 100644 index 6532888..0000000 --- a/posts/wifi-led-driver/resource/lyza_schematic_and_pcb.pdf +++ /dev/null |
