SpeedTwin Update

Recently I’ve been focussed on finishing off my radio controlled model SpeedTwin ST-2. This guy is not the biggest model I’ve built in terms of wingspan, but it wins in terms of chunkiness and complexity. I started it in 2012, but it stalled at some point because everything was blocked by scary “one shot or it’s ruined” style tasks. I recently dug it out and decided to get these things over with so I could get it back on track.

This thing is pretty huge!

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Foobot is a project I started around November 2014. It’s still a work in progress, but the time when I should have written it up is more than due.


Foobot is robot table football game, with two teams of two tiny adorable robots. The robots are controlled by classic Nintendo and Sega controllers, hopefully it can can finally settle the age old console wars. :)

Foobot Robots

The intention eventually is to build some games around these robots. Possibly with the ability for a computer to control some of the robots via some image processing if I’m feeling really ambitious.

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Finished Tricopter

I’ve been neglecting this blog recently due to various distractions but have several projects I want to write up. Around April I found myself with the urge to build a multicopter. In the end I settled on a tricopter design as it’s a little unusual and because the wider angle between the arms allows plenty of clearance to mount a camera without getting the propellors in frame.

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Simple PCB drilling jig

Drilling jig in action

Recently I’ve been making a lot of printed circuit boards. One of the common problems I run into is aligning holes correctly when hand drilling. This is especially troublesome on boards with large arrays of pins, such as my hexapod controller (I promise I’ll write that up soon!). A misaligned hole will prevent IC sockets from fitting correctly or cause pin headers to sit at crazy angles. This is really obvious on the first version of my hexapod controller board as shown below.

Wonky pin headers

In order to work around this for the second version of the hexapod board I used my CNC machine to drill the holes. This is great for relatively large jobs, but the setup time makes it less attractive for small one off boards.

Since I was scheduled to have an induction on Nottingham Hackspace’s new laser cutter and given the option of cutting my own project during the induction, I came up with a simple mechanical solution to drilling holes at the 0.1 inch spacing required for most IC sockets and pin headers.

Simple PCB Drilling Jig

The concept is very simple: a zigzag line is cut through a piece of plywood with a “wavelength” of 0.1 inches. One side of the cut is clamped to the work surface of a pillar dril,l and the board to be drilled is taped to the other side. The serrated edges can be moved around, and when pushed back together they naturally align to multiples of 0.1 inch. I went with a sawtooth style wave in the end so pressure can be applied in towards the flat edge of the sawtooth without the piece slipping.

Drilling jig in action

The photo above shows masking tape, but double sided tape would have worked better if I’d had any with me when taking the photos.

In order to make grid style layouts I added a second layer of serrations at 90 degrees to the first. I’ve not had chance to test this as the work area of the pillar drill I’ve been using does not have space. The intended usage is that both of the outer stages would be clamped in place and the inner piece manipulated by hand to drill columns of holes. Once a column is complete the middle stage would be un-clamped, adjusted then re-clamped. This is repeated for as many columns as necessary.

I’ve used the jig with a single stage on a few boards now, and it works well so long as the initial hole is well aligned. An easy way to ensure this is to align the drill bit with the smallest hole in the row and then clamp the jig in place.

To ensure that the board is aligned correctly in the jig, I usually find the longest run of holes on the board and put a ruler against the edge. Drawing a pencil line along the ruler provides alignment marks on the board that can be matched up with the etched lines on the jig.

In the current version, the inner section of the jig is a sacrificial piece which will eventually become full of holes. I toyed with the idea of making the inner section in an L shape into which the board would fit, but this would rely on the edges of the board being cut exactly parallel with the grid so it’s less useful in practice. Hopefully the sacrificial part of the jig will last long enough, and it’s cheap enough to just make another when it wears out.

FTDI breakout breakout

Earlier today I used the jig to make a very simple breakout board to match the pinout from an FTDI board to an Arduino style six pin header. The 6 pin header and 32 pin (minus 4 due to the weird layout on the FTDI board) IC socket I used fitted perfectly first time.

Perfect fit

I’ve made the CAD drawing for the jig available to download. Hopefully it will be useful to someone.


Arcade Control Panels

Charlie’s SuperGun had me inspired to build my own at some point, but I thought I’d start at the other end and build some appropriate controllers first. Partly as a birthday present to myself I decided to make a pair of arcade control panels.

After a long time reading SlagCoin, I settled upon a fairly simple box design with a joystick and 6 buttons on the front face and a pair of buttons on the left and right. I eventually settled on a black and white theme, with a black Perspex face plate and white buttons.

Finished Controller

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Loot of the Forest

I just finished participating in the 28th Ludum Dare game jam. This time around the theme was ‘You Only Get One’.

I chose to interpret this fairly literally as a game mechanic and came up with Loot of the Forest. It’s a game about bribing forest guardian creatures as you make your way through their forest maze, but you only have a single item per species of guardian.

Loot of the Forest

Loot of the Forest

Expect puzzles and weird animal based puns.

Play it here.

The game was written in HTML5/Javascript, with graphics drawn in GIMP, and sound effects generated by the awesome . It was fueled by sleep deprivation and cold pizza.


I’ve been a bit quiet on here for a while, and slacking on the PCB milling experiments I’ve been meaning to do, though I have made some progress on that front.

Anyway, here’s what I got sidetracked by building:

This is a small budget hexapod, using 18 of the cheapest servos I could find (£2.50 each). It uses a custom board with a power supply and 3 shift registers to control the servos. This in turn is controlled through an SPI bus to a Minimus USB AVR board, pretending to be a USB to serial device. The data sent over the serial line is interpreted as servo IDs followed by the desired position of the servo.

Mark 2 servo controller board

Mark 2 servo controller board

The control software I wrote for the hexapod can run on any Linux computer with a USB port. For dev I use a netbook but it also runs nicely on a Raspberry Pi.

The original plan was to use the Raspberry Pi’s SPI port to control the servo board directly, unfortunately due to Linux’s scheduling not being particularly real time even in real time mode there was a lot of timing jitter leading to real life servo jitter. Switching to the Minimus meant having a very dedicated if much slower CPU generating the pulses resulting in much smoother control of the servos.



I’ll hopefully post a full making of post on the hexapod soon, but for now I just wanted to post a video of some stomping!