Water Master
In my Toy Product Design class, I worked with 5 other students to create a toy that fit into a "Dream" theme. After brainstorming dozens of ideas for a week, we narrowed down to three ideas. I took lead on creating prototypes for Water Master, a water-based toy that shot more water the faster the user punched. We also wanted to add a feature where when the user made different hand gestures, the water would shoot in different ways (stream vs spray).
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In the first round of rapid prototyping, I worked on the "plays like" prototype to simulate the play value of our toy. To do this, I thought to create an LED rig that would light up based on the user's punch speed, creating a carnival-like strongman game, where more LEDs lit up when the user punched faster.
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Using an accelerometer and Arduino, I searched through countless libraries on Github for the proper accelerometer code, adjusting the existing code to fit our project. After some initial testing, I adjusted the threshold for the accelerometer in the code by increasing its max reading to 8Gs.
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Next, I connected an ultrasonic sensor to the prototype so it could read the proximity of the user's hand. If the user raised their hand in front of the sensor, it signified one hand position. This event would change the LED's color, corresponding to a different spray pattern.
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Finally, I needed to create the housing for the prototype. Using blue foam, I created an outer shell that contained the electronics and shaved away the bottom so it could be strapped to a user's arm.
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With the prototype finished, I ran tests by asking people around MIT's campus to give it a try. By collecting their punch data, I was able to properly tweak the thresholds for the LED lights for a test with children at the Boston Children's Museum.
In the next set of prototypes, we focused more on how the water shooter was mounted on the user's arm with all the bulky electronics, as well as incorporating water and waterproofing into our prototype. From our playtesting, we found users didn't care as much about the different spray patterns, and adjusting the thresholds for the different speeds of punching was too inconsistent to pursue. Thus, in this prototype, I rewired the Arduino to trigger a valve rather than the LEDs and adjusted the code to have a single universal speed that anyone could trigger with a punch.
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Then, as a team, we worked on a waterproof container to house the electronics and the valve. We created boxes with foam core so it had more structure. Then, we ran a hose from a container with a pump to a valve which would open and close if the accelerometer detected a punching movement.
However, after testing we realized that there were 3 main issues with our current design. It was too heavy for a user to realistically hold the valve and electronics on their arm, we would need a large container for water so users could enjoy more play without having to refill their containers, and we need something more than an accelerometer to detect punches and shoot water.
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Thus, as we transition into our final prototype, we moved all the electronics and water storage into a small backpack. Then, we led wires and a hose down to a small box that housed the hose and accelerometer, which could be mounted to users' arms.
In addition, we created a safety button that needed to be pressed before water could be shot out. The safety button was necessary because if the punch threshold was too high, people couldn't trigger the water to shoot, but if the threshold was too low, there was a lot more accidental firings.
Finally, we put all our electronics into a waterproof box which was placed into the backpack. To avoid the hassle of opening and closing the box, we also mounted a waterproof on/off switch on the backpack strap that users could easily access.
Water Master is a water gun that attaches to your arm. When you punch, Water Master releases a stream of water to douse your enemies!
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Built into it is a safety button that must be held before water can be released, so accidental spraying is minimized. To fill the Water Master, take out the canister held in the backpack. Once filled, pressurize the canister, and you're ready to go!
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Using an Arduino and accelerometer, Water Master detects punches based on acceleration which was tweaked to sense when a child punches.
