I had been thinking about this project for a while and got really inspired by Hans Forsberg's videos and comments. I wanted to make a very simple version of what he's been doing. I also wanted it to be small, cheap, using common analog components and discarded items.
I wanted to avoid programming and 3D printing - not that I don't love that stuff, but to keep this mechanically and electrically simple, cheap and accessible.
I hope this can be the type of project you can build easily, try it out and improve on it over time. There is a lot of room and possibilities for improvement and enhancement. Solar charging, cameras, computer vision, do it all with a microcontroller, print better parts, more efficient design... lots of room for improvement :)
I've already built a prototype and started testing it with birds that visit my balcony (mostly pigeons, but some jackdaws, crows and magpies). The vibration motor does not startle them - especially when they learn it means a peanut is coming,
The circuit is fairly straightforward:
- PIR sensor (the one thing I could not find laying around and had to buy. This turns on the rest of the circuit when triggered.
- 555 monostable vibrator to keep the circuit on for ~30 secs after the PIR is triggered. There is a diode leading from pin 6/7 to the trigger. This allows the PIR to reset the timer during a cycle, keeping the thing continuously on while a bird is in front of the PIR.
- LM358 dual op amp for the IR proximity sensors made from IR leds and phototransistors
- another 555 for a bistable vibrator - when the drop sensor sees something it turns the vibration motor on, when the dispense sensor sees something it turns it back off
- a third 555 astable vibrator - to use as an optional timed dispense to get birds used to it as a food source
- small DC motor (the one I used is marked 2 volts) with a slice of cork pressed on the axle and some screws in one side of the cork to make it vibrate
- some resistors, capacitors, a few transistors and diodes and signal LEDs to indicate what's going on
The circuit was the simple part.
Biggest problem I had to solve was dispensing one (or maybe two) peanuts at a time reliably without a complex mechanism or making peanut butter. A vibration feeder made from two jar lids with offset holes finally did the trick. This was a challenging puzzle to solve. I probably spent most of the project time on this.
The next one was sunlight - some leaks and reflections were triggering the sensors. Some foil tape and a better enclosure fixed this.
One interesting thing I discovered was that black shrink tubing did not trigger the IR proximity sensors, making it a great material to use as a backstop, letting you turn up the sensitivity a bit without extending the range - great for monitoring openings and chutes for passing objects.
Only the PIR and the FEEDER ON/OFF (monostable vibrator) are on until the PIR is triggered.
If it's in timer mode, the TIMER (astable vibrator) is also on.
- PIR sensor triggers monostable vibrator
- 555 Monostable vibrator turns on rest of circuit via an NPN transistor and keeps it on for ~30 sec after the last PIR trigger
- Deposit sensor detects passing object and triggers op amp 1
- Op amp 1 triggers bistable vibrator to go high
- Bistable vibrator turns on vibration motor via an NPN transistor
- Dispense sensor detects a passing peanut and triggers op amp 2
- Op amp 2 triggers bistable vibrator to go low
- Bistable vibrator turns off vibration motor via an NPN transistor
The above is still true, but in addition:
- 555 astable vibrator completes ~50 min cycle and its output goes high to trigger
- NPN transistor to turn on the sensors and motor switch
- NPN transistor to turn on the motor
- Dispense cycle triggered as described above
The schematics in the project description should be readable. It's broken into modules, but the interconnections are labelled.
- For the monostable, bistable...