I’ve gone back to working on the led cube. I’m using a great design for the supports but the power supply support boards for each panel don’t fit my particular led boards. So I’ve started making my own. Because the designs of these things have to change a bit I’ve made the program as flexible as possible. If you want an OpenSCAD program that you can use to make a plate with holes and rectangles in, then this could be just want you want.
It turns out that sometimes the only way to find out how to do something is to try and do it. That’s what I’ve been doing today. I’m building a cube out of LED panels. And today I ran out of reasons not to start assembling the parts. Above you can see one of the led panels that are going to be the faces of my cube. I’ve removed the original chassis from the back of the panel and fitted one that I printed yesterday. The new chassis is slimmer and has bevelled edges that let the sides fit closely together.
My printed panel fits exactly (more power to you Una the Ultimaker). I just had to remove the teeny tiny screws that secure the panel to the original chassis and then refit them into the the newly printed chassis. This is a fraught business. The screws engage with really tiny holes in the panel circuit board. If the screws miss their holes they tend to cut through tracks on the panel (that’s one panel broken). If you try to line up the panel with the chassis by pushing a pin through the hole in the pcb board this can catch on the leds on the front of the panel and remove them (that’s two panels broken)….
I managed to fix one broken panel by scraping the paint off and then re-making the connection with a blob of solder. The other panel has three LEDs on one edge which don’t light up red. Oh well. I ordered one extra panel in case of problems like this and I can still use my “broken” one in a picture frame as I just have to crop out that three pixel column from the side. On the whole, I’m going to call this progress…
If you want to see the work in progress I’ll be taking all my bits to the Hardware Meetup tomorrow. You can sign up here.
Una, my 3D printer has been behaving wonderfully over the last few days. She’s been turning out beautiful speaker covers. I knew it had to end sometime…. The above print is my first attempt at a panel support for the LED cube. It’s a right old mess. I used “gyroid” support because it sounded cool. That might have been a mistake. But the bigger mistake was to print the whole thing upside down. This means that all the support is in the wrong place, impossible to remove, and ruining the top surface. Hopefully it will print better next time.
My dreams of a led panel cube have been on hold for the last couple of weeks while I wait for the panels to arrive from China. Today I did something I should have done a while back. I did some digging to find out what was going on. Turns out that my local Parcel Force depot had sent all the letters about a customs payment to the wrong address. This raises a couple of depressing thoughts:
They must have a process where a post person reads the address off the parcel and then enters it into a different system to send out the letter. Amazing. Rather than have something automatic they have a process which is guaranteed to introduce errors every now and then.
Rather than pondering why I might not have responded to their first letter and maybe checked that the address they were using was right they just sent another reminder to the wrong address. So, once they have got a system that is prone to failure they then take no action when it might be possible that it has failed.
Anyhoo, if you have an AliExpress (other suppliers are available) package that seems to be stuck it turns out that sorting this out is very easy.
Use the ParcelForce site to find the package – the Aliexpress tracking number works here: https://www.parcelforce.com/track-trace
Find the depot phone number. York Depot is: 01904 888512, you can find other depots here: https://www.parcelforce.com/depot-finder
Ring the number. They just need your postcode and you can pay the duty there and then.
The panels arrive tomorrow. Here’s hoping.
Yesterday I ordered the panels for my LED cube. Today I find out that number one son has got a set for quite a bit less money from a different supplier. This should not annoy me. It is not as if the price I paid was too high, and I can afford it. However, it does annoy me. Does this make me a bad person?
We’re taking our first steps in building a LED cube. I dug out some of my old panels and we tried running them from a Raspberry Pi 4 with the Adafruit LED Panel Bonnet. We made the tweak described here to use the Raspberry Pi sound hardware to generate some of the display waveforms. This improves display stability at the price of disabling sound output from the Pi. This seems a trade well worth making, in that after the update the panel display was glitch free.
The led panels are interesting. I’ve used them with an ESP32 in the past. The way that the hardware works, only one in 32 rows of pixels are turned on at any given time. The host device must repeatedly light up all the pixels in sequence. It gets even more tricky if you want to control the brightness of individual pixels as this must be performed using pulse width modulation of the multiplexed display.
The word on the street is that a Raspberry Pi 4 can drive 6 panels of 64x64 pixels. We’ve not gone beyond 3 panels of 32x32, but we are hopeful.
Next step is to order the panels….
I really want one of these. As does number one son. In fact I think we’re going to build some.
Rob Miles is technology author and educator who spent many years as a lecturer in Computer Science at the University of Hull. He is also a Microsoft Developer Technologies MVP. He is into technology, teaching and photography. He is the author of the World Famous C# Yellow Book and almost as handsome as he thinks he is.
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