Turing Machine and Maker Faire

Here's a video I shot at Maker Faire UK 2011. I took the Turing machine along having just rebuilt it without testing, but it worked fine over the weekend after a little prodding and adjustment. I don't think everybody understood it, but everyone was positive about it and those that did understand what it did seemed very amused by it.

I didn't get much chance to have a look around the rest of Maker Faire, but it was an excellent event with some great minds getting together to create some great hacks (a video of Kinect controlled Tesla coils is doing the rounds at the moment).

Now that deadline's over, I can go back to the drawing board and start thinking about how to make a more reliable, precise version of this machine, or a more powerful machine which could actually demonstrate something useful - which would be better than explaining that this Turing machine would take months to add two numbers together.

3D printed cellular automaton

Work on the Turing machine continues steadily, but in the meantime I have been working on a backup plan for Maker Faire. Since I have a fair amount of spare time when I can't get to London Hackspace to do stuff with drills and hacksaws, I started work on a 3D printable automaton. The result is in the video above. It's missing two levers since I plain forgot to include them in the order, and this prevents it from actually computing anything - but this video shows the robot reading input data and altering the output data. When the levers are in place, it'll only move some of the output data, thus doing something interesting.



The input data is the row of ball bearings on the bottom of this video. They're all ones for the purpose of this video. The output data starts off as all zeros, and gets set to ones as the machine moves along. In doing so, the machine calculates the (n+1)th row of a rule 110 cellular automaton (top row) based on the nth row (bottom row).




Although it's a lot simpler than my mechanical Turing machine, it does exactly the same function - but it needs replacing manually at the end of each row (generation). Moving in only one direction is a really big deal, and makes everything much simpler.

Both this and the Turing machine will be on display at Maker Faire UK next weekend in Newcastle (12th & 13th March). At least one of them will be working, but sadly I've had to forego steam power in order to run it indoors.

Turing machine preview video

Here's some video I shot at London Hackspace last weekend. The machine isn't working properly, but this should show roughly what it'll look like when it does. There's some mild swearing on the soundtrack; mute it if that offends you.

I'll be back at the Hackspace tomorrow, making another lifter (5th revision!) which should make it easier to pick up ball bearings and allow more space for a better centering system when the ball bearings are returned to the track.

I've been accepted to Maker Faire UK in Newcastle in March - I'll have the machine running on a stand there with some more cellular automata stuff. See you there hopefully.

December machinery

The Turing machine ran three instructions in a row on Wednesday morning. I caught the 9am Tuesday train down to London Hackspace and worked through till 9am on Wednesday. The only problem remaining is getting the ball bearings to land reliably on the correct grid space. Direction change and movement are all solved problems now. I've added a gate released by an existing cam to stop the ball bearings exiting the machine too quickly, but the ball bearings often miss their correct grid spots.

This can be fixed by placing guards onto the grid, but I really want to avoid modifying the grid. Modifying an infinite tape requires infinite effort.

BigTrak + IGEP

So here's what I've done with the BigTrak so far. I've mounted the IGEP on the back, mbed in the nose and arranged battery power for all the electronics and set up WiFi to remote control it. Boring technical details are at http://www.srimech.com/projects/bigtrak/. The audio on the video is poor, sorry about that. I wanted to be able to hear the motors and my voice is pretty soft at the best of times.

Annoyingly, the biggest challenge by far has been getting the drivers working on the IGEP. It's a neat board, but not very popular so there isn't much community support out there for it. It took me a couple of weeks to get WiFi and usb-acm (necessary to talk to the mbed) working at the same time, and the next challenge is to get it to recognise a USB webcam.

November Turing machine update

Had a couple of days to work on the Turing machine during November. It's now on its fourth revision lifter, this time there are two lifting arms, one which will stop at the top of the state box and the second containing the magnets which will continue on, so the magnets are separated from the ball bearings at the top. This seems much more reliable. It needs a longer movement on the string which lifts the arms up, so there's a pulley system to double the effect of the cam lever. I've also made some changes to the reversing mechanism, using a weight which is just slightly stably balanced so requiring a very small force to switch over to the other direction. This should be operating at the end of another day's work.

Robot Hackday success

Nearly three years ago I wrote a little blog post about the MUTR micro rover kit which I'd just received then. I put together a basic rolling chassis then but then got distracted and didn't do anything more with it - until this opportunity came up.

Enter Robot Hackday, a day organised by MadLab and HacMan. People bring down old electronic junk and attempt to make automata out of them. We succeeded in making an army of wonderful robots, from scribblebots and shaking Altoids tins to furry tanks with glowing eyes. It was great to have a bit of banter with other hackers as we tried to get a robot ready within the day. One of the special guests this year was Tim Hunkin, a hero of mine since he presented The Secret Life of Machines many years ago. Tim's a really friendly chap and he spent ages helping me get my robot working.

In the photo is WrigglyBot, the robot I built on the day. I seem to have been photobombed by a robotic raptor. Someone else there (I forgot your name, sorry) named it as the front of the chassis ended up low enough to the ground to scrape chewing gum off the floor. The axles needed trimming to fit both gearboxes side-by-side, and then I drilled holes for the rear axle and redrilled the rear wheels so they were loose on the axle. There are three relays controlling the motor, one does the forward/reverse control for each motors, and the third is the main on/off control for both. As it stands, it can't run just one track at a time.

The relays are switched by the ever popular ULN2803 chip, and the whole caboodle is orchestrated by an mbed board. This is the first thing I've used an mbed for, and apart from a minor panic when MadLab's wifi left me without access to the mbed online compiler, it worked very nicely - certainly a lot less hassle to program than my usual microcontrollers. There's two batteries on board - the main 4x C cell runs everything, and would have run the mbed but it kept resetting when I switched the motors on, so I put in a separate 9v battery to run that.

The only problem is the clip-in worm gear sets. The worms tend to rise up when the gearbox is put under strain, and this will strip the gears if allowed to run for too long. Mine was still slipping despite lots of Araldite and wire holding the motors down. I think they need something to hold the worms down at the front.

Thanks to everyone at MadLab and HacMan, that was a great day out.