Rachel’s “Pig in a Bucket”

Rachel’s original design of the “Pig in a Bucket” is shown in the photo below, bottom centre. She wanted her pig to make sounds when you squeezed its nose. We have also added sensors to the ears!

Group photo, showing Rachel's "Pig in a Bucket" at the front.

Group photo, showing Rachel’s “Pig in a Bucket” at the front.

This is still a work in progress, and although much of the hardware has been constructed, the sensors for the nose and ears have yet to be built. Here is what we have so far.

There’s a hole in my bucket ..

We started with a plain galvanised 15l steel bucket, and then cut the bottom out of the bucket with a jigsaw to provide access to the electronics (when they are fitted). The hole had quite a rough edge after using the jigsaw, so this was flattened down with a planishing hammer and dolly!

Galvanised steel bucket with bottom cut out.

Galvanised steel bucket with the bottom cut out.

A small hole was also drilled in the side of the bucket for fitting the on/off/volume switch. The electronics are mounted on a wooden panel that fits into the bucket near the bottom, but leaving enough room for the electronics. The photo that follows shows some of the electronics mounted onto the board:

Amp and speaker mounted on base board - the Arduino was removed for this picture.

Amp and speaker mounted on base board – the Arduino was removed for this picture.

The board was glued into place in the bucket, so that it does not fall out:

Base board glued into place

Base board glued into place near the bottom of the bucket

Rear view of bucket showing the base board with the electronics mounted. You can see the on/off/volume switch at the side of the bucket. The sound is produced by an Adafruit WaveShield attached to an Arduino Uno. The sound is fed through a 3.5W mono Kemo amplifier and into a 5W Visaton full range speaker. There is a small amount of buzz which I haven’t managed to remove, but it is not noticeable when the sound is playing. The whole thing is powered by a 1000mAh Turnigy Li-Po RC battery, as they are light and powerful.

Electronics mounted onto base board and glued into the bucket

Bottom view – Electronics mounted onto base board and glued into the bucket

The bucket still needs to be decorated (as per Rachel’s design), the pig fitting and the sensors fitting to the pig. We’re hoping to complete this part by next week ready for the next workshop at MERL.

Below – we are attaching the new nose (containing an off the shelf pressure sensor) and the ears (which each contain a pressure sensor constructed form resistive plastic). The pressure sensor in the nose is situated between the cream coloured foam and the pink foam which forms the end of the nose (which Kate made independently, and managed to get the dimensions spot on!). It was intended as a ‘push’ sensor, so pushing on the end of the nose would trigger the sound, but it also appears to work well when squeezed, which is an added bonus.

Adding the new nose and ears to the pig

Adding the new nose and ears to the pig

The ears were more difficult to construct. We wanted the whole area of the ear to work as a sensor, rather than an isolated area, which would be the case if we used a small off the shelf pressure sensor. So we used conductive (copper taffeta) fabric with resistive plastic (Velostat) sandwiched in between. The resistive plastic becomes more conductive the harder you squeeze it, so it works like a simple variable resistor.

Constructing the ears

Constructing the ears from resistive plastic and conductive fabric

One downside to the construction of the ears was that they have to be kept flat. Bending them would lose the resistivity. We did (obviously) try to create curved ears, but they were very inconsistent in operation and unreliable. Hence we stuck with flat ears and made sure they were attached to the pig flat! The wires were attached (using ordinary wire) to the ears by sewing them with conductive thread to the tabs at the bottom (see image below), and then gluing in place:

Squeeze sensor ears for the pig in a bucket

Squeeze sensor ears for the pig in a bucket

There was also a slight bug in the software when we initially tested it out, but it was easy to solve, and the finished item is below. It’s beautifully colourful!

Rachel's 'Pig-in-a-bucket'

Rachel’s ‘Pig-in-a-bucket’

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