Jan 31, 2024

This Vending Machine Rewards Birds for Their Labor

Humans are successful as a species because we have the intelligence to bend nature to our will. We didn't like being cold, so we built condos and central heating. We didn't like being hungry, so we invented agriculture, factory farming, and genetic modification. But our endless quest for comfort and convenience has led to a lot of environmental issues, such as litter. It would be great if we could convince nature to pick up after us, and Stephen Chasey found a way to achieve that with a vending machine that rewards birds when they deposit trash.

Chasey found inspiration in the work of Hans Forsberg, who trained birds to exchange litter for morsels of food. Birds are intelligent and it doesn't take them long to figure out how the trades work. Chasey liked the idea and wanted to adopt it, but wanted the vending machine to be more affordable. His version is easier to build with scrap material and traditional tools—no 3D printing or laser cutting necessary. He also wanted to avoid digital components that would require programming.

The machine Chasey designed utilizes mostly analog components. Most of us would have turned to a microcontroller for a project like this, but Chasey realized that it would be possible to control everything with standard sensors and components like op-amps and 555 timers.

The process starts when a bird lands next to the machine and triggers a PIR sensor, which activates the rest of the circuit. Then a monostable vibrator built with a 555 timer waits for around 24 seconds. If nothing happens during that time, the circuit turns off. But if the bird drops something into the collection chute in that time, it will pass in front of infrared proximity sensors. An LM358 dual op-amp boosts the signal from those sensors, triggering another 555 timer-based monostable vibrator that drives the dispenser motor. The dispenser will run for 11 seconds or until more infrared sensors detect food falling out. Then the system turns off and waits for a bird to trigger the PIR sensor again.

This design is efficient and very flexible, which makes it practical to deploy at scale. While there are sure to be unexpected downsides, a whole fleet of these vending machines around a city would keep birds fed while also removing litter from the streets.