Showing posts from 2015


I've now got a Python webserver up an running (on my Linux server, for now), which offers a list of modes for the user to select from. When a mode is selected, it uses jQuery to push this back to the webserver, which then tells the other thread to change which animation it should play.

It's on Github, obviously -

The letters have arrived too, and I had to re-jig the LED layout a bit. It was tricky to get something that lines up in nice neat rows, but I think I got there in the end. After a few goes on the computer using LibreOffice Draw, I decided to just use chads from a hole punch to get the layout right.

Christmas with a Pi Zero

I picked up a couple of Raspberry Pi Zeroes (plus one with the Mag Pi magazine, which I'm not going to open) when they went on sale. It's Christmas, so what better than a Christmas Pi project?

While in the local garden centre, I saw a Christmas ornament I quite liked - the word XMAS in MDF lit up with LEDs. But they were just regular LEDs, and that's dull. An idea formed.

The project is underway, but here's where we are so far:

Four letters (X, M, A and S) ordered in MDF from I considered making the letters myself, but I don't yet have access to the scroll-saw at work and I figured I'd just make a mess doing it by hand. I'll put up some photos when they arrive. I've gone for a flat bottomed Arial Bold, as the serif fonts are generally asymmetric and that messes with the LED layout.

40 off WS2811 5mm Neo-Pixel LEDs ordered from The standard LED format will be so much cleaner when mounted in the letters than the more common …

Back to our regular programming

A recent holiday gave me time to catch up on things. One of them was the electronics to control the automatic signalling for my model railway.
I found an interesting chip from ONsemi. The NCV7608 is a 8-way FET driver with SPI interface. The particularly useful feature is that it exposes both drain and source on each of the 8 output FETs, allowing it to be used for high-side and low-side applications.
A small PCB with an NCV7608 could operate 8 colour signalling aspects, regardless of whether they were wired common-anode or common-cathode and regardless of the voltage the resistors were set for. With an RDS(on) of 1.2 ohms, the chip can source (or sink) a fair amount of current before going pop, so you could also use it as a relay driver to operate points (although perhaps driving the points directly might be a bit ambitious).
I feel some Eagling coming on.

New bike!

I decided to switch from taking the bus to work, to cycling. As it's about 14 miles each way, I thought the best starting point as an electric bike. Then, if it's a howling gale or horizontal rain, I'll still be able to make the journey without collapsing.

The bike I chose was the Kudos Tourer with Nexus 8-speed Hub. It's quite an interesting setup, and not very well documented, so I thought it was worth a few notes.

The battery pack slides on to a shelf on the rear pannier. It is a 36V nominal 10Ah pack, which charges up to 42 V open circuit. It has a key switch and the battery management and balancing must be internal. There is a four pin socket on the back, of which two pins are connected, and an RCA phono jack under the handle for charging. The charger is from Sans and its rated output is 42V 2A. My first battery wouldn't charge and my second had an intermittent cutout. Hopefully my third will be reliable!

The battery power comes into a hollow plastic box stuff…