Turing-Welchman Bombe physical build – part 8.

August 19th, 2015

Well, a bit of a setback today. I replaced my main board with a new one that is using latches so the second and third drums hold their position much better between steps. That worked great. Except then when running through a Bombe run nothing would work properly! For some reason the motion of the drums was very uneven and jerky. I spent hours last night trying to figure out why and in the end went to sleep with the problem unsolved. Today, at lunchtime, I decided to take a 5 minute break from work and give it another try. Unfortunately I was rushing and I accidentally plugged my 12 volt battery into the 5 volt rail. No magic smoke escaped from anywhere but my Raspberry Pi got killed! They do contain some voltage protection, including a polyfuse, so it may come right. If not I will have to get another. So far then this project has claimed the life of one Arduino and one Raspberry Pi!

In the meantime I was rethinking the design and am going to try running it in a different way. Previously the Pi told the Arduino when to make the drums step and stop. This is one reason the motion was jerky I think. It relied on me sending the pulses very accurately from the Pi end. I have reworked it so now the Arduino effectively free runs but it sends pulses to the Pi every letter it steps. The Pi can then tell it when to stop. I think this should work much better. I have updated the Arduino software to do this (without the signals from the Pi yet) and it is MUCH better. I have made a little film to show this since I am too lazy to do a big write up today and because my friend Dani, a teacher, keeps telling me off for my chronic abuse of commas.

The other thing I did was order a little USB back plate. I am going to remove one of the connectors and mount it on the Bombe backplate for the Menu USB stick to plug into.

IMG_4304_1 IMG_4305_1 IMG_4306_1



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