Marc's Public Blog - Electronics Hacking

The daughter board looks like this:

and the back looks like this, input for 12V power from the motherboard and Vret to make 3.3V

Then, because I was reckless, I swapped M2 cards while the PC was powered, thinking they were hot swappable like Sata, but they sure are not. Eventually I caused a partial failure of the board. Gemini helped me debug the linux errors from the cards plugged in itand confirmed my guess that the voltage regulator on the board was now partially damaged and gave power, but not enough to be reliable under load.
A new daughterboard is only $20, but that's 2 week shipping from China while my new server would be down. So, it actually knew the daughterboard, it knew where to buy it from and the shipping delay, and it also knew how it was made before I gave it my picture. It confirmed that the best course of action would be to desolder the 100 component that was an inductor, and I could just unsolder it and connect a new 3.3V source to it.

After helping me find a new 5A Vreg on amazon, it looked at the picture of the board, and it confirmed the top pad, is the one feeding 3.3V to the rest of the board. It suggested I use flux to help unsolder the SMD component after I declined the suggestion to use a hot air gun that would be too likely to remove other components, some of which had to be useful:

yes, it looked ugly, but the inductor was removed safely, I then cleaned the flux

Then I happened to have the right female connector in my collection of cables and plugs (happy it does come handy at least a few times), and soldered in the new Vreg:

I had to move it on the other side so it would fit with the case closed

And there you go, I literally fixed the daughterboard and the PC works again! Yeah! I honestly was impressed by Gemini's knowledge of existing boards and its ability to read pictures I sent it, identify the components and confirm test points and how to verify I was adding the new power source in the correct place.

Back to work!

so these batteries that do not look great (and they are not), are legal, but powerbanks are not.

So you're going to tell me, why don't you put those unsafe looking batteries in an enclosure? Great question, when I did that airport security wanted me to open the enclosure to see the battery inside and its readings. How about you make it professional and write the battery reading on the other side, and then add a plug to connect your things to it? Well, that's exactly what a powerbank is and those are not allowed anymore (past 2, which is a useless number for me).

See the problem? I need exactly 5 powerbanks to run my LED outfit, LED backpack, and spare charger for phone and camera. This is with no spares, often I need a 6th for a long night. This does not count powerbanks for my laptop if I end up in a plane without working power. Now you see how it's easy to get to 10 or more and why the new '2 max' really f'ing sucks.

So what are the other options?

Does it surprise you that airport folks said those batteries looked like shit? Of course they did, and that's why I worked hard to replace them with powerbanks that looked a lot better.

Seriously, fuck, this sucks, now I need to replace 10 powerbanks that were not cheap and carry less safe ones because of this idiocy. Welcome back to the past, self made crap that will not look better or be safer, but somehow is legal

History of the LED outfit:

So, why a version 8? Well, the flexible panels in v7 were nice and light, but the flexible part made them break repeatedly. The chip solder points in the back would eventually fail, causing different kinds of failures on the panels, and I had to replace them in the field (even carry spares with me). This was not a long term solution, never mind that my spares were running out and it was probably impossible to buy matching panels today.

When I said things broke, I often had to repair the outfit while at festivals. Initially repairing panels was a lot of work, and required a soldering iron. Version 7 was designed to allow easier panel replacement with just a screwdriver, but I still needed to prepare the spare panels at home (soldering them before they were needed), and I broke almost 10 in 1.5 years. This was not sustainable:

Another issue was that I would lose pixels as they would eventually fall off on the other side, and the plastic cutting board I used as a diffuser and protection layeer, helped, but was not sufficient. My favorite vendor, Hongren Su from Azerone, had a new GOB coating to protect the pixels and and even make them water proof, but he didn't have anymore legacy style panels, just new PWM panels which were not supported by the rpi-rgbpanels library that I use. Those new panels are better in theory since they self refresh at 2khz or so, but they all need a separate incompatible driver, which is a huge pain in the ass. By sheer luck, Kingdoc9 on github had the same problem and somehow managed to use a coding AI to make a driver for a few chips. Total hero!

At the same time, adafruit made an active-3 low profile board which is not ideal since it covers the CPU, hinders cooling and points the connectors up, but it's better than the electrodragon low profile passive 3 board:

And still at the same time (talk about me being lucky), Hongren Su from Azerone, nicely offered to make a custom metal frame for me, with 5 degree bend, which solved both the problem of panels breaking due to repeated flexing, but also significantly simplified mounting of new panels as I only had to slap them on and the magnets did the rest (and boy those magnets are strong):

new versus old, piece of wood used to stir paint, and 3mm screws with limited reach

trying both boards

Now another vexing failure point I had, was the ribbon cables from front panels to rear ones. I used a trick to only drive the front panels with a Raspberry Pi and had ribbon cables to pick up the signal coming out of the front panels, and feeding it to the rear panels. This was a great idea, it ran the rear panels for free, I didn't have to have a 2nd rPi in the rear and saved on power.
But, as there is always a but, wearing the panels, put stress on the ribbon cables and they would eventually break. I did put straps that would get the stress and in theory prevent those failures, but they still happened, worse by then it was the HUB75 plug on the panels that would fail. That was very annoying as it caused my rear panels to have display bugs after the plugs were losing pins and there was nothing I could do short of replacing the entire panel:

note the straps to protect the HUB75 cables

this was supposed remove stress from the HUB75 plugs, but didn't do well enough

there are the HUB75 plugs that would fail

with the new setup, 2 computers (really 4 with the ESP32s), no more ribbon cables front to back

One other build optimization is I did what I should have done a long time ago, which was to use the fat power cables to send power around. Those cables even have ends that plug directly into my 20V-5V DC-DC converter. Why did I not do that earlier and insisted on using JST 2 pin cables everywhere (which I had to solder on each new panel). As an added bonus, those big power cables are thick enough that a single one going across to the back (the only connection between the 2), is enough. In the process I also removed 2 straps between the mid and top panels, as they were unsightly and now unnecessary:

So the new build runs both screens independently:

while both sides are setup to display the same thing, they render independently. This is not a problem of course

Now, I had to write a fair amount of ESP32 code (I used gemini for help), so that the 2 chips would coordinate, the front one would be master (selected by switch) and the rear would listen for a broadcast, become slave, and send its IP to the master. The master would then send a UDP command to the slave to update the pattern every time the master changed. End result:

This is how it works with remote control:

Same communcation panel to panel;

People sometimes ask me if I can "just add" a graphics on the fly. In real life I have to use gimp to shrink the graphic to 128x192 or close to it and convert to gif, it takes a little while:

The new driver is not as fast as the old driver in pushing data to the panels (yet), so I had issues with tearing in some animations as the panel refresh was happening half way through a slower frame push to the panels. I had to fix this by implementing double buffering, and you see the before vs after (left panel vs right panel):

Now, the only problem I have left is increasing the panel refresh from the Pi3as, so that they hopefully allow the panels to refresh faster and not show these half refresh screens. Never a dull moment :)

0.004s

0.002s

0.001s

0.001s

this will more or less fit :)

nothing really looked wrong, but the power supply was dead

So I ripped out the power supply, connected a 2.5mm jack female, and now any external 5V power supply will do the job:

new fan spinning on happy switch

back online

The solution was to find the right dimming/blinking controller, which was quite hard to locate (didn't want to build my own). Uper right is most of the ones I found, they were too big, did dimming but not blinking, also they were USB based, so I have to solder JST connectors. Lower right is a better version, still USB only, although at least it had flashing. And then I finally found the right ones, bare wires, easier to just solder in my JST connectors, and they support flashing and blinking:

new board this year, radio communicator

People working hard:

and fun stuff

Met someone who made LED shoes, which predictably broke because they can't take the flexing:

I came decked out:

Random slides and talks:

SAOs are still fun things to play:

Evening parties:

A fun workshop was a 64x64 matrix connected to an ESP32 S3 with adafruit shield, I actually ended up spending more time on that because blinky :):

a new badge :)

Good times, looking forward to next year