The hardware for the project can be broken down in to 2 main sections – the electronic control of the various sensors and the mechanism to dispense the nuts.
A) Electronic control.
Having played around a bit with breadboard I’ve worked out what I’d like to have for the various inputs and outputs:
1. Motor to drive the nut delivery system behind a reed switch or relay.
2. Microswitch to tell the pi where the motor is – to stop it chucking out tons of nuts or none at all!
3. Motion detector – I’ve bough one from Tandy which works pretty well .Not sure of the use for it yet but I:m going to add it in should it be necessary in the future.
4. Switch to trigger if the nuts are deployed. (possibly an IR breaker beam rather than a switch to avoid complex mechanical issues).
5. LED. A light that I can configure to show different colours. I’ve chosen a RGB LED so that it can be positioned in one place with the colours showing the status – I’d considered several different coloured ones but was concerned that the wildlife would notice the position of the light (i/e 3rd from left) rather than the colour = possibly a new experiment, though.
I wanted something that was easy to connect to the pi and so have come up with a veroboard circuit that connects to the pi via a ribbon cable.
This has the various connectors in place to make it fairly easy to connect up the swiitches etc and the ribbon cable to ensure that they are alwas connected to the correct pins on the pi.
The second piece of veroboard has the connection for the lego motor – these have special connectors and I decided to use an old battery box as a doner for the plug. I then soldered this on to some board and glued it down having worked out the pin arrangement from here: http://www.philohome.com/pf/pf.htm
It all works pretty well however the wires are inclined to come off the pins at the slightest vibration! Also I’ve had trouble passing 9v through the opto isolator as it sticks at anything over 3v – I’ve since got some relays that may prove better.