Final Project: The Final Post

Here is a description of our project, which includes highlights from all previous posts:

Our device is intended to be a teaching device in the bathroom, showing proper steps with adequate timing of hand washing. A few things we kept in mind while designing the project include the needs of child development, the versatility of the device for other similar uses, accessibility/ease to change batteries and other parts inside, and the environment where the device will be installed (water proof ability).

The device consists of a box made of Delrin that supports and contains all the structure and electronics of the device. The top is open for easy access of the battery box and Arduino, since versatility and flexibility are key to our client. The sides are covered by plastic wrap, which allows the child to observe what happens inside the device for curiosity reasons but also prevents water from coming in. The visual demonstration is secured in the front by velcro.

The input of the device comes from the ultrasonic sensor at the bottom of the device facing forward. It is secured by screws, lego, and velcro. It reads whether there are objects in front of it every 0.1 second. Once it detects a person at the sink, it would re-confirm after 4.5 seconds to make sure the person is still at the place, so that people walking by would not trigger the washing process.

The output of the device includes a servo and an LED. The servo starts turning after the 5-second reconfirmation. It would rotate 16 degrees for each step of the washing process. This circular movement is translated into a linear motion by a 1:5 gear train (8-tooth and 40-tooth gears) attached to a chain, which moves the indicator by around 2''. The LED blinks when the ultrasonic sensor detects someone in front of the device. It will then remain on for the whole process once the sensor re-confirms the person is still present. This helps troubleshoot. In case the indicator does not move, we can know if it's the problem with the mechanics of the gear train, or it is the sensor that fails to detect.

Here is a video of how our project works. Note that the first hand wave represents a person walking by but not stopping.

Here is a picture of us with our project!

Reflections

To be honest, our final product is not what I'm most satisfied with for the semester. Nonetheless, I still learned many things.

The first lesson we learned is reality! As I mentioned in my first post, I was very obsessed with the idea of using a tree the turns green as the children wash their hands for long enough. Now that I think about it, while it is a smart and simplistic idea, it is certainly not as effective as our current model for our purpose, which is to teach the children. We also initially wanted to include a sensor that detects whether the water is turned off. This turned out to be too much to be done given the time we have. There are numerous instances when we had to adjust our goals based on the reality (even with time or material available). I think this is the most interesting and challenging part about engineering (and the most different from Math, my major)! I can dream big in ideal situations, but I also must be flexible in reality. This is certainly a change for me, since I am the kind of person who likes to plan things out perfectly. I would say that my skill with planning ahead allowed me to come up with multiple alternatives before I start building things, and makes it easier for me to be flexible. However, I cannot always predict everything. My experience with engineering so far really taught me how to deal with unpredictable circumstances calmly and with patience.

What I appreciate the most about this project is how we got to use almost everything we learned this semester. We incorporated laser cutting, lego, Arduino, sensors from Sciborg, as well as some soldering, filing, cutting, and heat staking. I was very pleasantly surprised how well we remembered each technique at the right time to apply to different parts. This project definitely created a chance for us to understand the materials we've studied in a holistic view.

Another thing we really learned is how important details are. Our project is not the most complicated among all, but it was by no means done in one try. There were so many details we had to pay attention to, such as what paper to use for the visual, what color to use for the indicator, what is the exact measurement between the axles, etc.

In terms of the product itself, there are a couple things to improve on, mainly the aesthetics.
I would like to build a complete box without the top. The front would have one slit open for the indicator to move. The visual would be secured by velcro to the rest of it. I would like two sides with big windows that allow children to watch the inside of the device. These windows can be sealed by plastic wraps from the inside. We can also color the box or have the children color the box, so it looks more than a plain white box.
I also feel like our project is not the most complicated. Granted, it does everything required, but I keep wonder if there are other things we could add to it. We could potentially add some sort of reward after the child successfully finishes the cycle. We could try to figure out sensing the water on and off. (This may be easier with sinks that have handles as opposed to a knob.)