Thursday, 29 April 2010

Formica Expansion boards have vision ... almost!

Today was the fourth day of assembling and testing our Formica Expansion Boards. The final set of components arrived, enabling us to finish assembling all the boards. We spent the morning getting all of the bump sensor to work. These consist of a pair of piezo transistors, a rectifier, filter and Schmitt trigger. The conditioned analogue piezo signal and the digital signal from the Schmitt trigger are connected to the MSP430. This will allow the possibility of doing something clever with the analogue signal in software to deduce something about the nature of the collision. I'd like to see texture recognition based on this principle at some stage, although this is beyond the scope of our project.

The final, assembled expansion pack will look very similar to the ones in the photos below:

This eye sensor are not soldered on yet, because we are still prototyping how to make the aperture. The picture below has this chip soldered on it and we successfully read a pixel dump from it earlier today. Unfortunately the PCB footprint for one of the capacitors on the eye PCB was wrong, which meant 3v3->GND shorts were really easy to induce while soldering.

In order to manufacture the antennas in a sane and reproducible way, Tom constructed a jig to make them:

Tuesday, 27 April 2010

First signs of life in Formica Expansion Board

Today we gained access to some surface mount soldering tools which ECS recently purchased. This meant we could solder on some of the more complex components such as the MSP430s. Particularly enjoyable was using the hot tweezers to rapidly solder on annoyingly small capacitors and resistors.

Below is a photo of the first signs of life from one of our expansion boards.

Unfortunately, while I was designing the board layout I reordered the programming pins (GND, DIO, CLK). This means that the programming adapters I have had to make to program Student Robotics boards are incompatible (GND, CLK, DIO). To get around this I made yet another adapter board. This lead to a rather unpleasant situation involving too many adapters. Here is a photo of the horror:

I think it is time I address this!

Monday, 26 April 2010

Ducklings on Campus

First spotting of Southampton university ducks:

Formica Expansion Boards Arrive!

As part of a final year group project I have been working to develop an expansion board for the Formica Robots. Over the Easter holidays I spent a considerable amount of time designing the PCB for the project. This is the first PCB which I have fully designed and had manufactured, so it was quite exciting. The boards arrived at the end of last week and so today (Monday) was the first chance I had to look at them and see if they work.
Here is the stack of ten boards fresh from PCB Train:

The white card behind them is a standard business card, which gives you some idea of how tiny these things are. These were then promptly cut with a PCB guillotine to separate the eyes from the expansion board:

Two eyes will stand vertically at the front of each expansion board, as the following mock up demonstrates:

The first problem experienced during construction is that the reverse of the inductor (shown in photo below) has a lot of exposed contact area. This is fine, except there is some ground plane and some signal lines routed directly under it on the board. To get around this I experimented with electrical tape stuck to insulate these tracks from the inductor.

LESSON #1: If you decide not to get a solder mask, be sure that you have not routed signals underneath components such as inductors, which have exposed conductive surfaces.

I have so far assembled only the DC-DC convert sub-circuit, due to the majority of the components being held captive by `stores' (My departments woefully inefficient system for ordering parts). Nonetheless, what has been built, works. This surprised me! The photo below shows the current state of assembly:

Saturday, 24 April 2010


The task of working out who owes who what amongst my flatmates was getting pretty complicated. There are always circular debts and bills being split amongst different groups of people. For these reasons I set about writing a program to do this for us. I have name it Pybill. It is written in Python and can be downloaded from gitorious:

git clone git:// 

Or visit the project page:

The program takes a csv file (bills.csv) as an input with the format:

payee, amount, debtors

The program then outputs the minimum number of cheques required to settle all of the bills. Each person is identified by a single character and groups can be defined similarly. At present these are hard coded at the start of the code, although I will change this to be a second CSV file soon. I am still in the process of testing the program but am confident that the algorithm to work out the payments is correct.

There are other freeware/shareware (mainly for windows) which claim to do this, along with many more websites which promise to do the same. However if you don't want all the guff that they come with, or want a simple file based solution then this may be useful.

Friday, 23 April 2010

First Barbecue of the Year

Last night my flatmates and I had our first barbecue of the year. This was the first time we used the home made barbecue that has lived in our back garden since we moved in. The barbecue itself is made from an oil drum, some door knobs off an old set of draws, an upturned shopping trolley and some chains taken off the plugs in the bathroom. We had nothing to do with the design! Of particular merit was the use of the sides from the shopping trolley as the grill.

Unfortunately, whilst it was a really good barbecue, the base of the oil drum rusted through and the legs of the shopping trolley came through it. It now has a sort of tilt to it which it didn't have before.

Playing with fire
Hot stuff
If I've said it once, I've said it fifty times. What this barbecue needs is *more* paraffin!

Burning sticks
Shopping trolley barbecue
Good times

My trident of fire

Long exposure fun
The tilt

Wednesday, 21 April 2010

Duck's Guide to 2010

Dizzy Duck
Power Tool Duck
Public service announcement duck
Scaffold duck
Technobooth Duck
Duck, Over!
Hacker Duck
George Duck
Ramp Duck
Duck at Home