Every project needs a main project box and this one is no different.
The box must be moisture proof, since that will keep out the cold and wet in the winter months and by being waterproof, that will keep out the red mites that love to feed on the chickens blood whilst they sleep - which can make them anemic and eventually die, they will find all manner of crevices to hide out in, so we must be vigilant when making the project.
We also need to get heat out and have all the wiring from the various sensors and controls coming into the box, so I selected a larger IP68 waterproof box from Maplin
Along the top and right, we have the various sized cable glands that allow us to make waterproof connections into the box. All are pre drilled, since its easier than adding more it at some point in the future when it's all wired up. All the unused ones have a 20mm piece of clear perspex rod inserted and are tightened up, hence maintaining the waterproof state of the box. These are easy to remove when necessary.
On the left is the user interface, this is made up of two 4 digit 7 segment displays, these are preferable over a more advanced TFT screens, since they work well at low and high temperature and various light levels. Below the displays are 4 buttons, some of which have integrated LED's. The displays are stuck in and waterproofed with some silicon sealant.
Inside the box is an aluminium base plate, since we cant drill holes into the back box and maintain the waterproof box, this is also a handy heat sink to spread the heat.
at the top are the obligatory 78 series linear voltage regulators to give us the required supply voltages from the only 12V power source - the lead acid battery, we have 6V and 5V for the door control servos and logic supply respectively.
At the top right, we have the Raspberry PI with the logic shifter board on top of it
Below the Pi is the power driver board, this provides the high power MOSFET driven outputs and all the power wiring. Everything is protected by a 20mm fuse, just in case - I'm thinking about the dry wood, copious amounts of straw and not having roast chickens again.