CharityBot

For a Hackathon on UT, I created in a team of 5 people an automatic charity vendor.

One of our group members runs a charity on campus for which he bakes cookies, and students can donate any amount of money they want to charity and they get a cookie in return. We wanted to take some of the work from his shoulders so we created a machine which collects money and gives cookies automatically.

The machine is shaped like an oven, for it contains freshly baked cookies, which can be viewed through the screen in the door of the oven.

As visible in the picture, there is a slot for coins on the right of the front side of the machine. If a person throws in a coin, the lamp with "READY" will burn and the door will automatically open. Then the user can take out a cookie. After a while the lamp with "PLEASE CLOSE THE DOOR" will burn and the user can close the door shut. The door is being held shut by a strong magnet.

During the design process, we found a working solution almost instantly. At first we thought of a way more difficult system, which would have cookies in different cabins in the machine, and the cabins would open using a motor to dispense the cookies. It would be a safer design but we didn't have enough time to make it. Instead we went for this design, we laser cut all the wood, 3D-printed the chef's hat, and constructed the entire thing from scratch.

The cookies go into the chamber on the left, and the entire circuitry is in the chamber on the right, hidden from view when the top of the oven is on. The circuit works by shining a light on a light sensor. When the light gets broken (by a coin), the sensor picks this up and sends a short signal to a pulse extender. (In technical terms an NE555 timer circuit). This longer signal enters and Arduino, which runs code to move a servo as long as the signal is being seen. When the signal stops, the servo turns back.

This servo pushes the door out of the range of the magnets so that it falls open.

The signal also changes which light is burning, either showing the person they can take out their cookie or telling the person to close the door.