Last week we added the ‘smell machine’ to the cow. This device is custom made for the cow, and circulates a single smell placed in a container inside the machine. The smell machine was 3D printed in parts and then assembled, rather like a model kit. You can see the container for the smell in the main image below – it’s the square orange thing sticking out of the side. When you remove it completely it opens up so that you can place a smell inside. It was designed so that a standard sized cotton wool pad could be soaked in a smell and placed in it.
The smell is circulated by a large computer fan (the big black thing), chosen for its fairly compact size but high air volume. When we tested it, the fan would move across the table by itself when on full power. There are also to servos on the smell machine which open and close a pair of butterfly valves. These are intended to keep the smell inside the machine when the fan is not blowing. Otherwise the smell will just come out by itself …
To control the smell machine, there is a small wooden control box containing a Pololu Micro maestro servo controller and a small circuit board with a MOSFET to switch the fan motor on and off. The Micro Maestro was chosen because it can be programmed to respond to input – it runs a simple script which waits for the button press, monitors the control for the number of seconds, controls the servos and sends the signal to the MOSFET. I can highly recommend them, and the scripting language is easy (a bit like FORTH, if you have ever used that).
On the front panel there is a power-on light, a green push button and a rotary control to select the number of seconds for the fan to blow. The operation is simple: select number of second for fan, and then press the button. The valves in the smell machine will open, the fan will blow for the set number of seconds, and then the valves will close.
Whilst the cow was resting on the sofa (see below) we added the smell machine underneath (not shown here) and also tied up all the loose wires, for which there are many. The next job is to add a power connector for the mains and also an on/off switch.
Next week we will be trying out the cow with a group of students from Reading college, so I hope all goes well.