Initially i’d hoped to dispense standard, roasted monkey nuts as the squirrels love them! I’ve built many variations of the dispensing mechanism out of foam card however it was proving to be really tricky with the irregularly shaped nuts and their friction.
I’ve tried all sorts of mechanism from the simple opening and shutting of a spring loaded door to the moving of gravity fed nuts using a cut out like the board game downfall.
The downfall was my favorite but very problematic with the monkey nuts so I changed to using shelled nuts which were much easier to dispense.
Above all the design needs to be reliable so I have constructed many prototypes with the most reliable by far being a simple trap door – I don’t mind it dispensing too many nuts at once however I don’t want it to clog up and this design proved to work well.
The whole thing needed to be motorised and the foam card just wasn’t strong enough so I reverted to creating the mechanism from Lego at this stage. This was an easy decision as I have tons of it ahnging about with the only downfall ( 😉 ) being that I didn’t want to conform to the lego standard dimensions however for a prototype it would be fine.
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.
Having made the decisions about the design of the feeder I needed to begin getting the basics of the pi set up together.
AS I’m going to be using RISC OS there are a couple of hurdles to overcome that aren’t present in linux.
The shopping list for the pi setup is:
1 – Remote access for running the program (or monitoring if autonomous).
2 – Wireless networking.
3 – Sending or recording video.
4 – Get it working from battery power.
Before I get to running wirelessly I thought I’d begin with accessing the pi from a remote computer using its current remote connection – For this I used the VNC server by Adrian Lees – http://adrianl.drobe.co.uk/
He describes this as a shaky alpha release but, while a bit slow, it is perfect for running my basic program.
I accessed it from the laptop using tightVNC which provided a good & stable connection. The pi is set up to display on my tv using hdmi and I didn’t want to fiddle with the screen resolution, so I wasn’t surprised when it didn’t like running at 256 colours.
The choice of housing has helped enormously as it gives me a decent set of physical parameters to work too with the design of the internal structure was governed by the required inputs and outputs.
1. a method of dispensing the nuts (e.g. motor)
2. a method of checking that the nuts are there.
3. a way of signaling to the wildlife that food is present.
4. a way of finding out if the nuts are gone.
5. A way of detecting if the feeder is being visited.
It would also be helpful if there was a method of filming the feeding either from the actual feeder itself or remotely from an unconnected camera.
I’d like to be able to have a configurable method of linking the different inputs and outputs together and the raspberry pi was the easy choice – its pretty small but more importantly I’ve got one so no further outlay!
I will need to create a way of running the pi outside so it will need a battery along with either some way of communicating (e.g. VNC) or to be totally autonomous..
I’m no programmer however as a child I enjoyed my acorn electron as well as having access to a BBC B and and Arc 440, reaching my programming pinnacle aged 11! A few years later I’m drawing on this skill and so would like the project to run using BASIC on RISC OS – mainly as I’m most familiar with the language (although I’m very poor at it) but also because RISC OS just seems to work so well on the pi. The issue with this is that it doesn’t support simple wi-fi dongles and getting VNC to work appears to be pretty tricky.
Finally the whole system needs to be both watertight (in case of showers) and reliable (so that I don’t keep disturbing the wildlife by resetting it every few minutes).
I’ve looked online to see if there was anything commercially available that I could either buy or use the ideas from – the closest was this as posted on the Raspberry pi website:
With our squirrels and jays becoming a bit more used to our presence I though it would be fun to create an automatic feeder. Rather than simply dispense nuts the idea was to get them to work for it and to see what they see in terms of colours. Initially this consisted of a coloured l.e.d. that showed if a nut was present (e.g. red for none, green for present etc) with the nut being obscured so they could only tell via the colours.
I have grown this idea in my head to the point where I thought it would be fun to construct a dispenser that had several functions and then use them in a modular fashion to create various scenarios for the creatures to go through before they received the prize.
This idea was left for a while until my niece & nephew gave me a bird house for my birthday – unfortunately it is not possible to put up a permanent bird house in our communal gardens but the shape of it made me think that I could build my dispenser inside – so I did!
The following posts show how I am going through the design and build of this project.