Marc's Public Blog - Electronics Hacking

Issues:

I had to melt the resin until I could expose the power pins

looked ok on the bench, did not work long in the shoe

shoving the battery in was not easy

it worked on the bench, but didn't work too long in real life, by then I added an external lipo plug to check the voltage and do fast charge, bypassing USB

By then, I had what I thought was a great idea: why don't I just forget about secondary batteries and use the external connector to power my shoes from my pants that already have 5V power on the neopixels?
This felt like a good idea, but first I had to add diodes to drop 0.7V so as not to exceed 4.3V for a direct connection to the lipo (as a remminder, I cannot connect via the USB plug as if you send power there, the shoe does in charging mode and stops lighting up), but then I found out that my neopixel strips did not actually have 5V at the end due to line loss, and it was going to be complex to safely connect them to my shoes without a voltage regulator and more electronics, making the whole thing, questionable. Still, it was a tempting idea for a short while to use my mega battery pack to power the shoes forever ;)

Of course, it's all nice and good until something shorts. Thankfully my foot didn't catch fire:

So for version 4, I had slightly better connection of the external lipo connection with hot glue around the module, but the more important part is I figured out it was better to attach a flat lipo on top of the shoe so it wouldn't get stepped on:

I also had spare modules and batteries in case of failure, and a way to charge them from USB outside the shoe:

By then I had run out of my old modules that slowly failed over time, and had to find a new shoe with compatible modules. Thankfully that one has slightly better firmware that allowed lighting one LED out of two:

A big thanks to IGxx for nicely sending me extra modules so I could hack on them and have spares. Here is the shoe I recommend you buy today: https://www.amazon.com/gp/product/B07GS6GSRY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

This is the new shoe with the updated module. Very pretty shoe, but otherwise the modules still have the same 4h runtime, and still need the same work, bummer:

battery goes up there so it's not stepped on

So yeah, we're now at v4, it still relies on unreliable soldering, and extra hot glue but at least the external wires are stronger, the external battery more than long enough for 12H+ of runtime

got a few extra colorful yard lights ;)

To debug some early issues I had with the pixelblaze, I soldered a few extra wires to add serial monitoring:

the serial port is temporarily going to a rPi3a which in turn makes it available over an ssh connection

up left if the pixelblaze pro expansion board that gives 8 channels, handles power distribution and converts the 12V to 5V for the pixelblaze itself

For the pixels, I picked rolls of 1000 pixels at 5cm and 10cm pitch from Ray Wu, trusted seller of blinky stuff, and one bonus of not doing this installation a few years earlier is that new pixels have been designed: WS2818.

The last bit "more efficient" actually worked to my advantage as I was able to make a string with 600 pixels and not have to re-inject power anywhere. I measured line voltage at the end and it was only 5V but the pixels still worked great at the reduced voltage.

The advice I got on the leds are awesome group was to try hot glue, and it was a good idea. Thankfully I had a battery powered hot glue gun, which was a must have. The other important bit was a solder reflow hot air gun, which did have to be plugged in the few times I had to unglue strips to move them after I found a better routing or visual pattern:

And in all, I actually need 3 tools, the 3rd one was a battery operated air can replacement which allowed me to blow cold air on the hot glue points and have them dry in 10 to 15 seconds instead of 1mn. That was a lifesaver:

After laying strips, house looked like this:

After the first 2 days of work, I had 4 strips, around 1500 LEDs:

or on youtube:

But it really got better once I added 2 more strips and upp'ed the count to 2000, which was a lot more visually pleasing:

or on youtube:

flexible 16x32 RGBpanel

found a hat big enough that it mostly fits on it

of course, it needed a few LEDs :)

what it looked inside and it worked with a small 1S 700mAh lipo (although not long enough)

bigger battery upgrade, and BTW those batteries lie, they are only 1600mAh

testing battery draw, a bit over 0.5A which is a bit too much

So, why 3-4V lipos instead of USB battery packs with 5V that is expected by both the panels and neopixels/WS2812? Well, space is limited, USB battery packs are kind of big, and carry extra hardware to recharge that isn't needed inside the hat. There is also a side byproduct that powering both the panels and the LEDs with a lower voltage, limits their brightness and the amount of power (watts) they need, which means that a 16Wh lipo inside a USB battery pack stepped up to 5V, makes everyting brighter, but only lasts about half as long as powering directly from the lipo at lower voltage.

bigger 4Ah 1S lipo worked for 8H at full power and LEDs worked all the way down to 2.8V!

panel worked all the way down to 3.4A before colors went wrong, 16H on a 1.6Ah battery

of course now I had to find a buy a faster 1S lipo charger with the right connectors (had to get JST adapters)

quick test that a smaller 700mAh battery would last around 5H before things got dim

After testing, I was able to confirm that both the $7 amazon controller (SP002E from https://www.amazon.com/gp/product/B09Y8SWJ77 ) and the RGBpanels, work fine with lower voltages (which is not a given since both run a microcontroller that was originally meant to be powered from 5V).
The RGBPanel controller is a bit more picky about voltage and reboots around 3.5V, while the neopixels tend to drag the battery voltage down, causing the RGBPanel to crash and reboot when a single battery runs both, so I gave it its own lipo.

Pixels still take 0.3 to 0.5A (I use a potentiometer to dial them down as the cheap controller I put has no dimming control) and the RGBPanel takes less than 0.1A, so that's nice (it actually goes all the way down to 0.05A or just 50mA) when the voltage drops.
The combined tricks should give around 18H of runtime with the 2 batteries (4Ah and 1.5Ah 1S lipos), which is enough for 17 hours of dreamstate (they are not screwing around this time, 17H !!!)

About the neopixel controller, I used a cheap $7 amazon controller that only had 3 physical buttons but sadly no dimming control, mostly because I wanted something very small, and while pixelblaze micro is also small, it doesn't have the pattern I want, and I didn't see the point of programming a pattern I already had on the other controller, so I just put a potentiometer to lower the voltage. It's obviously the wrong way to do it, but it works :)

Here is the end result:

1) Oh, I need to finish writing code to get the SAO badge holder to do something fun

2) Mmmh, why does this python global variable thing doessn't work in the function

3) Goes to re-learn python, with help from gemini and how python forks global variables by default in functions so what you write to them isn't saved at local scope (oh my, why did they do that?)

4) after more hacking, get a proper demo working:

5) publish code https://github.com/marcmerlin/2024-Supercon-8-Add-On-Badge/blob/main/README.md (actual code is here: https://github.com/marcmerlin/2024-Supercon-8-Add-On-Badge/blob/main/software/software/main.py )

6) Oh, I need to make a video demo of the SAO, but...

7) oh yeah, there was that hat on my desk I needed to add LEDs on for an upcoming party, start hacking on that

8) mmmh, the hat won't work long enough with a USB battery, start hacking on a lipo solution

9) ah, lipos work, but the front LED panels rated for 5V start failing around 3.5V, so I need to make a dual lipo solution, one for the neopixels and one for the RGB panels

10) test and measure the dual lipo solution and figure out it will last close to 12H, that's good. Ok, hat works mostly, post that https://www.instagram.com/p/DCYEl1jJd_-
11) Ah yes, the SAO video I was supposed to work on: https://www.youtube.com/watch?v=z7MSywf7js4

12) During that time, I get interesting distracting packages on my doorstep, like lovely flexible LED panels that will hopefully power my future outfit: https://rpi-rgb-led-matrix.discourse.group/t/rpi0-2w-speed-compared-to-rpi3a/913/2

13) While I'm testing them, also try some new rPi0 2w chips and microcontrollers to see if they can power my LED outfit with a smaller form factor (and yes they can): https://rpi-rgb-led-matrix.discourse.group/t/rpi0-2w-speed-compared-to-rpi3a/913 . In the interest of briefty, I'm going to skip the part that included migrating from raspbian to a new dietpi linux distro and port back all my custom changes on it :)

14) That said, I had a long-ish discussion and planning with the electrodragon folks in China on how to make a new 3 channel daughter board that is much smaller and would decrease the over footprint of all new picture frames like the one I built, and of course my LED outfit.

15) but wait, now I also find out there is a new beaglebone solution that does 6 channels output instead of 3? Ok, make a post about it: https://rpi-rgb-led-matrix.discourse.group/t/interesting-6-port-board-beaglebone-pocketcroller-v2/918/2

16) and file a couple of RFE bugs to look into it: https://github.com/hzeller/rpi-rgb-led-matrix/issues/1733 + https://github.com/FalconChristmas/fpp/issues/2054

17) Oh, I just found this old video on my laptop, why did I never post it? Ok, fix that: https://marc.merlins.org/perso/linux/post_2021-01-23_Linux_conf_au-2021-LED-Talk.html

18) Mmmh, so when I quickly posted those pictures from Neil deGrasse Tyson who just gave a talk, I got a reminder it was annoying for my blog system not to be able to link to videos directly without having to upload them to youtube.

19) Ok, learn about html5 video tag, hack my blog system to support videos, and push a new blog with my first video tag: https://marc.merlins.org/perso/outings/post_2024-11-14_Neil-deGrasse-Tyson-back-at-San-Jose-Center-for-Performing-Arts_-An-Astrophysicist-Goes-To-The-Movies_-the-Sequel.html

20) ok, but why did I have to rescue my video from my phone because the H265 recompressed version did not work in the blog? Ah, because of royalties on H265 being too high, most browsers refuse to add support for it: http://marc.merlins.org/perso/linux/post_2024-11-17_Vidrename-Script_-Clean-up-Normalize-Video-Filenames-and-Add-Codec-And-Container-Format-With-Mplayer.html

21) Ok, sure, but now I need to upgrade my vidcomp script to support VP9 and AV1: http://marc.merlins.org/perso/linux/post_2024-11-17_Vidcomp-Script_-recompress-videos-on-linux-with-mencoder-or-ffmpeg-to-div3_-div4_-div5_-xvid_-mpeg4_-h264_-h265_-VP9_-and-AV1.html

22) then I find an Email from a chinese engineer who is willing to talk to me about making better LED shoes. That's exciting, let me reply to him first

23) ok, now I can recompress my videos to VP9, which I benchmarked to somehow be faster to compress and still smaller file size than AV1 (not supposed to be the case, but that's what I'm getting). On the plus side, VP9 works with more browsers than AV1.

24) what as I doing again? (now days have passed). Oh yes, I was supposed to write a blog on hackaday supercon: http://marc.merlins.org/perso/electronics/post_2024-11-01_Pasadena-Hackaday-Supercon-2024.html

25) of course the ridiculous amount of time spent to allow these 2 videos in that post, is a bit hard to justify, but it's really solving a problem I've had for over 10 years, and never got to the top of the pile, because, well, you see what happens when I try to put something on top of the pile :)

26) and I was good, I didn't even play with the micropython rpi micro I received in the mail this week, or the electromage pixelblaze and I/O board, or more LED panels that somehow showed up at my doorstep :)

27) mmmh, and there are all those webcams I ordered and need to configure, but now it's clear I'm going to have to re-install my camera controller, shinobi, from scratch, and that's yet another rabithole...

28) in the meantime I have to finish my LED hat, and design my new shirt and pants for Dreamstate in 4 days... Wish me luck :)

SAO stands for Shitty Add Ons, all explained here:

A challenging SAO that was offered to me was the "Yo Dawg, I heard you like SAOs in your SAOs", which including some micro SAOs that were challenging to solder. That was an excuse for me to learn SMD soldering with solder paste, flux paste, and the heat gun I had.

links:

I didn't do a great job, but it worked, which is what mattered. The motherboard was easy to solder with a real soldering iron, but this micro SAO was the challenging one:

The micro SAO didn't really have clear indications on positive vs negative, so I had to test the board and LEDs to make sure they were in the correct direction:

They, I had to lay out the components:

Cover with solder paste and flux:

oh boy, not looking pretty :)

And after heat gun, things mostly went into place:

And it worked!

Success!

It was very cool that I got to wear my LCA SAO badges for the first time:

This post, because of its 2 video inserts, a new addition to my blogging software, was also an interesting exercise in non linear time and tasks, more on this page: Getting Things Done in an ADHD World

Day 1, Friday

Thanks to Anthony for letting me know about it, and I was able to attend. Went there early on friday for the pre-conf to work on the badges:

the conference badge was this 6 port micropython rPi micro with a couple of SAOs.

they nicely provided food all 3 days

essential geek survival food :)

They gave us a quick primer on how the badge worked, although it would have been better on a webpage with links and info for total beginners who had never used micropython and thorny or knew what thorny was (that included me):

I'm glad I took pictures of these slides, they only made sense many hours later. They should have been online

finding fellow LED geeks :)

learning blinkies for beginners, scan this

While I was there, I 9ound out they had a wonderful 4 bit computer some years back. I actually really regret not having been there that year, programming that in hand crafted assembly would have been epic:

someone hacked a basic I2C on it

people now hard at work

I used the opportunity to bring previous LCA toys and show them off (and fix a few)

People came with plenty of SAOs:

some came more ready than me :)

SAO extenders, cool!

SOA badge holder bag, sweet!

I found Tom Verbeure, the person who had been hacking on RGB Panels with open source FPGAs (colorlight). Cool project for sure. See: https://github.com/q3k/chubby75?tab=readme-ov-file#colorlight-5a-75b and https://github.com/lucysrausch/colorlight-led-cube/tree/master

Also, finally got to meet Henner Zeller, the rpi-rgb-panels author I've been working online with for years:

epic watch!

Also got to meet Daryll Strauss from precision insight, later acquired by VA Linux some 25+ years ago:

People still hacking at night:

I was lit up enough not to get lost :)

Day 2-3, Saturday & Sunday

went to attend a few talks

hacking radio sound and B&W video from a chip, super cool!

learned about an online microcontroller emulator, wokwi, very nice

who thought SAOs were a simple standard? :)

I got to see a pick and place machine, nice to see them work and glad we don't have to do this by hand:

this is what the machine was 'printing'

I tried the SMD challenge, that was hard as hell:

we got old and fat irons, making things harder :)

I couldn't get the last 2 LEDs working, they were so stupidly small

I had someone help me fix mine :)

and they all worked, thank you to the master solderer!

added the result on my badge :)

Random fun shots :)

people hard at work

During the weekend, the SAO wall got populated:

Original from Burning Man

more and more

and more :)

Saturday evening party had a nice real time AI image generator:

some were far out :)

The conf ended with a presentation of best SAOs:

This guy won the contest of biggest SAO, he had a printer working off USB, run by his SAO

Sunday ended with a party at a bar, thankfully I had my battery soldering iron :)

This was loads of fun, and I definitely learned some good stuff. Sad I didn't go earlier but glad I went this year. Thanks bunch to all the organizers and attendeers who contributed!

And I also made 2 pages on SAOs:

More pictures: https://photos.app.goo.gl/2hYRaaB5dF5mvv4N8

In 2021 I got my first SAO Conference Badge from Linux.conf.au (clickme for more) That LCA board had 4 SAO ports and came with 2 little cute penguins that I hacked a bit:

one of them was then in charge of running a neopixel necklace

I got a few spare SAOs to attach to my heavily hacked LCA badge :)

Anyway, back to Pasadena Hackaday Supercon 2024, they gave us a 6 SAO badge also running a micropython chip:

attendees nicely donated a few extra SAOs to me, which I wrote code for

even got an SAO extender :)

I had to solder it from parts at the after party in the pub

Oh, and has homework, I got a micro-SAO (Yo Dawg) with SMD Soldering to do at home (click me) [*SMD*/209*]

Back to the conf SAO and code I wrote, here is the result:

Micropython Code:

Main repo:

This was loads of fun, thanks to the organizers!

They are of course not all the same real usable capacity, and I've learned not to trust vendor capacity claims anymore either, due to the amount of sellers that plain lie on amazon. The good news is that Neither Xtar nor EBL lied about their cell capacity as long as you understand that the actual energy you can output will be lower due to conversion losses and some safety buffer to give the cell longer longevity.

https://docs.google.com/document/d/1z9o7O5o70SxJnQwKHJD8JdlPdScZZ1o09scHqUlDxeE/edit?usp=sharing

Here is a quick summary without pictures:

New Xtar: Rating: 4.15Wh, Charge: 5.5Wh, 3.45Wh Usable discharge at 1A

Old Xtar: Rating: 3.3Wh, Charge: 5.3Wh, 2.7Wh Usable discharge at 1A

10.6Wh to charge 2 batteries, or 5.3Wh charge per battery

EBL 3.3Wh rating, Charge: 4.3Wh, 2.7Wh usable discharge at 1A

Summary:

Deleepow 3.4Wh rating, 3.8Wh charge, 2.4Wh usable discharge at 1A

Summary:

Just like last year, Illuminaughty was about as far across the playa as a camp can be, so it was nice when we arrived :)

Ran into a bunch of people will cool gear:

Very cool hat:

Impressed that the newer panels can bend pretty well

a lot of work went into these patterns

Anthony had a lot of cool gear he built, I was very impressed:

Obligatory group picture:

Thank you to Chuck for organizing this year again, it was lots of fun.

And if you want even more details and history >>> See this full article on the why and evolution of my LED outfit <<<

For all these years, my outfit has relied on a fanny pack filled with batteries, and with an unslightly tether from the fanny pack to the panels, bringing 2 feeds with 5V (as backup and to spread out the amps over 2 wires). That system worked for many years and would survive the failure of one of the 2 5V connections, or even the 16V connection meant to feed the rPi from its own power source stepped down to 5V on the panels (so that it doesn't see a voltage dip on the remote 5V rail when the display sare fairly bright). All in all, it worked, but the fanny pack tether and wires were cumbersome, and some security folks didn't like all the wires.

After switching to a new neopixel controller that is directly USB powered, it made more sense to power the panels locally and put the batteries on the panels:

For comparison, the old panel on the left only has the rPi and a small 16B to 5V converter and than relies on that tether cable to the white box on the left which has the DC-DC step down and the ESP32:

finished design with padding, power routing from 3 lipos or 2 USB attery packs

While this was not new for v6, made sure the camera still worked, it turns out to not be super reliable on batteries, but when it works, it's a crowd favorite:

The new version works like the old one, but with batteries directly attached to the panels, which in turn makes them much heavier, but oh well. Video with Lipos and DC-DC converter:

However, the more interesting upside is that I could also replace the 16V lips that get stepped down to 5V, with 5V USB Battery packs. the reason I never did that at the time is that the entire system takes way more than the maybe 2.5A you can get from USB packs on a good day. A somewhat cumbersome workaround to this problem is to use 2 USB battery packs with 2 independent outputs each, meaning 4 independent 5V busses able to put out up to 2.5A depending on the battery pack. So, I split my power system in 4:

In total it means the whole thing uses about 3A at 5V, or 15W, which means 180Wh for 12h. In theory 2x 99Wh battery packs would work for 10H, but in real life, the first battery pack gets a lot more load since it runs the rPi, so it only really lasts about 7H before I have to replace it. Not ideal, but still nice that I can run from USB instead of lipos if needed:

Video of the USB version:

After some unfortunate feedback soon after I built the new version, I added a makeshift back cover with duct tape, mostly to hide the "scary" electronics, while still giving me accesss to them since this is still a prototype that needed occasional work and tweaks:

Since the original design with lipos, the good news is that lipo chargers have finally become much smaller. They are now small enough that I can simply leave one in my travel backpack forever:

Now I don't need this "custom made" battery box ;) which worked for its time, but didn't allow bigger batteries being an issue during 12H festivals (2 batteries wasn't enough), and was an issue during airport inspections when they wanted to "see inside the box":

I however found out over time that some airports really didn't like to see the panels in X-Ray with batteries attached. All airports were fine with the panels on their own, and the batteries on their own, but if I left the batteries in the outfit, which honestly is a lot more convenient to me, some airports really freaked out in totally irrational ways and now complained about "too many wires" "looks like a bomb" and all that good stuff. The 2 airports that delayed me enough that I barely made my flight (bangkok and Ontario, CA), literally said they would have been fine if I had packed the batteries together and still carried everything I was carrying, just not plugged in (of course everything was off, and plugged in is actually safer since you don't have loose power connectors that could somehow short).
So I'm not interested in missing a plane due to this and honestly nonsensical and irrational reactions (after all, no one said fear was rational or logical), so I eventually made a "battery pack" that I can more easily slide in and out before and after each flight:

Oh yes, it's still home made looking, could somehow get/make a box for it, but if I do they'll want to open it to see inside, going back to the original box I had earlier, so I'm not sure there is a good way to win this. Also if I make it look too much like one battery instead of 3, they'll complain it's 290Wh (over the limit) instead of 3x 98Wh (under the limit).

And to show how things evolved, this was the v3 outfit with neopixels and only 24x32 instead of 128x192, but much brighter. I did use v3 a couple of times again at day festivals, as it can be made bright enough to work in full daylight, but after doing this a few times (and that required extra batteries), I decided not to bother anymore, and skip the LED panel during day hours (I still have LEDs on arms and legs that can be made bright enough if need be):

Separately, I often have to explain to people, that my outfit is actually a scaled down version of the RGBPanels you see on stage. Once you have the display, it can scale up:

And another question I get is "how long does it last?". 2 batteries of my old 5Ah 4S lipos, was a bit short for an all night 12H festival (EDC), but back then I was also powering the LEDs on my arms and legs, which took an additional non trivial amount of power. For wiring ease, the LEDs are now on a separate battery, which allows the main system to run longer. I also upgraded the batteries from 5Ah to 6.7Ah. As a result, I found out a bit after the fact that actually 2 batteries would have been enough, since I put 3 as per my old setup, I ended up with a full runtime of just under 19H (I stopped the test before the batteries were totally drained since it's not great for them to do so). As I'm writing this, I now realize that with just 2 batteries, I could last 12.5H, which is still more than enough (and it would remove some weight, so I may want to consider that.

310Wh out of my 3 batteries, more than I thought, and almost 19H

because all meters have measurement errors, recharging pushed back in 20.4Ah instead of 21.2Ah which doesn't quite add up, but close enough