Smart Trash – Physical Computing Final

Katie and I worked together on this project as our Physical Computing Final.

This project started as an attempt to apply what we had learned in our physical computing class to street furniture. Both Katie and I are fairly urban oriented (natives of Detroit and NYC respectively) and were eager to connect our new ITP knowledge with our prior interests.  The trash can emerged as our point of focus since its probably the most ubiquitous form of street furniture and one of the least interactive. Over the course of this project I think we learned valuable lessons in terms of our approach to interactive work and completing physical projects in general.



Once we had selected the trash can as object of interest we spent some time looking at different types of cans, reccent ideas in this area and doing some field research.


We reached a number of important conclusions about trash behaviors:

  • Many people do not want to hold onto “garbage” for an extended period of time
  • Many people do not want to litter
  • Many people do not want to touch a public trash can and will avoid doing so even if it means littering
  • Many people would like to recycle but are frustrated by the lack of trash differentiation

These user behaviors work together to produce some strange results :

One of the most technological trash cans in wide spread use is the Big Belly solar compactor. The advantage with these cans is that they are self contained (self powered), aware of how full they are,  relatively easy to clean out, and most importantly they compact the garbage as the can fills. This decreases both the number of trash receptacles required for a given area and the frequency at which they need to be cleaned out. This saves a lot of time and money for any agency that is responsible for keeping streets clean. The glaring failure of the Big Belly trash cans in our opinion and (others) is that they require the user to grab a handle to open and close a little door to deposit their trash. As a result in this has become a fairly common scene in NYC neighborhoods where these have been deployed: 

(Thanks to Jordan Frand)

In addition to user behavior we also identified a number of other key points about street trash:

  • Geography is important – E.g. trash receptacles near a fast food restaurant will overflow with trash related to that business while an empty can might be down the street
  • Collection is the primary concern – Getting people to recycle or put their trash in the trash can doesn’t matter if theres no one to pick it up and deal with it.
  • Cost and durability – Street furniture needs to be durable and affordable on a large scale

Based on these findings we came up with a few directions for improvement.  We wanted to have the can open and close as a way to better contain the garbage inside of it, to protect from wind and rain, and to indicate if the can was full. We knew we wanted this opening and closing to be hands free and to be interesting/entertaining for people so that they thought more about their interaction with the garbage can. We wanted to build a system where additional components could be attached easily depending on the needs for that specific geography. One example of this in action was made by Sandra Hoj out of a tube for used coffee cups.

We also wanted this “system” to sit ontop of existing garbage cans in NYC. In reviewing the types of trash cans suitable for street use we discovered that the common light metal mesh cans cost around $100-250 while heavier cans that don’t fall over as easily can cost up to $850. We thought that this gave us an interesting opportunity to create a product that attached to the lighter, more easily moved and cleaned models that would make the total cost less than a heavier model. Lastly in followup conversations with Tom Igoe, our professor, we thought that data collection would be an important goal as well. Measuring the weight and volume of garbage would give us a diagnostic tool that could be used to determine what attachments or design changes worked and didn’t work.



In developing our product we had to repeatedly revise, scale back, and pivot in many areas. Our final product ended up being very different from what we set out to do but going from concept to creation was definitely educational. We initially focused on developing the lid and opening mechanism that we thought would serve as the base for our motor, sensors, and other attachments. As we thought about opening and closing mechanisms we wanted something that was visually interesting but also quick enough to prevent garbage from spilling out if the can was knocked over. Ultimately we landed on trying to produce an iris diaphragm. Our first attempts at building an Iris were promising but as we scaled up we ran into a constant stream of problems.


Our first Iris


We made over four different Iris’ with a ton of help from our classmate Franklin using different materials and designs but each of them failed for one reason or another (sources we used for Iris design 1,2,3) . With certain designs the issue seemed to be materials but then it would be hardware or problems with the gears for the motor. Honestly, I don’t really know why we had so much trouble with the Iris but I suspect that the designs we were using didn’t scale up to the size we needed it to be with our level of precision. Lacking a base to build the rest of our trash system and the time it took to build each Iris sent us scrambling. While we had most of the electronics laid out and programed not having anything to attach them to left us at dead end. (Video of electronics coming)

Using what we had available we built a different type of closure and built a box around our prototype trash can to act as the housing for the electronics.

Due to our time crunch we primarily focused on the opening and closing interaction. We had the lid slide open using a stepper motor, stop, determine if their was still motion happening in the view a motion sensor, and if not close again. In addition to this we used a trio of FSR sensors on the bottom of the can to detect changes in weight. If the can detected that something had been placed inside it would let out a short three tone sound to let the user know that their contribution was welcomed. Lastly we had a trip ball sensor that would disable the opening and closing response if the can was not right side up. Here is a video of the final product in action (SmarTrash).

While I certainly would have preferred to build something closer to our original concept I am grateful for the experience I gained in this attempt and and happy with the final product as a demonstration of the skills I’ve acquired in physical computing and elsewhere at ITP this semester.

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