Power over Ethernet, LaserDiscs, miscellaneous projects
In my last electronics-related post I mentioned I'd been working on a few projects. It's about three months since then, so lets give some updates and talk about new projects!
LaserDisc Player
As mentioned, a few of us at the hackspace were trying to fix a VP406 LaserDisc player. Originally it was sort of working - it was playing a disc but the video was shifted to one side. You could see the colourbursts from the PAL video signal on the disc. This hinted that it could be an issue with the remodulation, which it apparently does to try and improve video quality. While debugging that, several other things seemed to go wrong. We ended up on a wild tangent of reverse engineering the ROMs in Ghidra, which pointed us to a signal with incorrect timing. We managed to get that working, but now something else isn't working and the disc spins up, keeps spinning up faster, and doesn't stop trying to spin up. We ran out of steam a bit and have put this project on hold, but there's detailed notes over on the Nottinghack Wiki.
GPIB Addon for the Glasgow Interface Explorer
This was a bit of a fun adventure FPGA stuff, which I'd done before. There was much to learn, and whitequark was exceptionally helpful. I made a small PCB with a GPIB socket, and the applet successfully captures data from an oscilloscope and other bits of test equipment. This wasn't the first time I'd messed around with GPIB. I'd replicated a project to use an Arduino as a GPIB adapter, and also written a 2.11BSD driver for the IBV11 GPIB controller on the PDP-11. Anyway, the pull request is still open. There was a lot of other activity in the glasgow project at the time, but I think it put some code review on hold. We'll come back to it eventually I think.
Hackspace Radiation
I've had a Geiger counter sitting in my drawer for a couple of years. It was one of those cheap-ish kits you can get off eBay. Since I have a Radiacode (the bast portable radiation detector ever), I didn't have much use for it. Wanting to put it to use, I modified the code on one of the LED matrix displays at the hackspace to count the number of pulses and push it to MQTT. It's now being displayed on the hackspace grafana. Unsurprisingly, someone strapped an Americium source (a smoke detector) to it within a couple of days.
Measuring Vibrations
While I was messing about with grafana and the radiation detector, I was thinking about the incredibly loud people above us at the hackspace. We are below a dance school, and while it's mostly small children dancing, they sound like elephants when they are jumping about in tandem. We make our own fair share of noise, so I don't mind too much, but I was curious about the type of vibration. Also, it's free data to graph… There is now an Arduino strapped to the ceiling with a WizNet ethernet hat, and some kind of accelerometer (I can't remember which one). Running on the Arduino is the ArduinoFFT library, which is putting the amount of vibration into frequency bins and pushing to MQTT. I'm not sure how useful this is, and I've yet to notice any kind of trend, but it's fun.
Power over Ethernet
One of the network switches starting acting up recently at the hackspace and we didn't have any sparse left. I decided to order a pair of Cisco 2960S switches - they're gigabit and I'm quite comfortable with the Cisco IOS interface. I think they accidentally sent the PoE variant. While I've used plenty of PoE devices in the past, combining it with some of my recent electronics projects made me curious about how PoE works.
I did some web trawling and found an interesting post about implementing Power over Ethernet. It doesn't talk much about the ethernet side of things, but goes into plenty of detail about a circuit to get power. I decided to implement my own, using the same MP8007 and Coilcraft transformer as the post, but tie it in with an Arduino and a WizNet W5500 controller.
The boards arrived earlier this week, and surprisingly the PoE part works fine. What I wasn't expecting was the WizNet to have problems - I've built quite a few boards at this point which have both the Arduino and the WizNet on board, so found this quite confusing. It mostly didn't work, but would occasionally start working for brief moments. I decided to adjust some of the traces and add more vias. After submitting the board to JLCPCB though, they asked me for another $80 to do via tenting and kelvin testing, pointing out that my vias were too small. Urgh, I hate big vias, but perhaps this is the problem. When I last uploaded the design files, I didn't have this issue, but the vias were still small. Anyway, I've made them bigger now, so we'll see if the WizNet starts working on the next version.
As a brief side note, we recently ran a pledge drive for a Pixel Pump. For those that don't know, this is where a bunch of us pool some money into buying a new tool for the space. It arrived, and we printed the case and put it all together. For placing chips it is far easier than using tweezers. For placing small resistors etc, I think I prefer tweezers, but it works well for both.
As another side note, since I mentioned pledge drivers, I ran another pledge drive at the space for a neon sign. I'm very excited and will post pictures once it's done. I'm glad many other hackspace members were as enthusiastic about this as I am, or at least, enthusiastic enough to pledge towards it.
Anything else?
Not sure really. Although back on January 1st 2025, I placed an order for a MNT Pocket Reform kit. At the time it said it would be dispatched within a couple of months - obviously it's now August, but last week I received the dispatch email. It should arrive on Friday, so once that's up and running I will have to attempt to write a blog post from it.
Related posts:
Wanting to leave a comment?
Comments and feedback are welcome by email (aaron@nospam-aaronsplace.co.uk).