My First Hardware Startup: Rimo (9)

Rimo in an ice cream shape

[ This series of articles is about my startup company, Rimo, from the conception of the idea, recruiting a team, producing prototypes, to fundraising. ]

HatchDuo presented us with five different designs. They believed that Rimo could be made smaller if we removed the motor responsible for up and down rotation, allowing Rimo to only rotate 360 degrees horizontally. Additionally, they removed the phone holder, reducing the number of parts and opting for a slot-in design, making it more convenient for users to plug in their phones. All five designs were based on these two points, but with unique styles. For example, the first design resembled a donut, the third looked like a mochi, and the last one looked like an ice cream scoop on a plate. HatchDuo was clearly confident in their designs, assuring us that they could produce any of them. However, I was a bit nervous because no matter which design we chose, the circuit board would definitely need to be redesigned to fit.

Different Rimo designs Different Rimo designs Rimo in an ice cream shape

Ultimately, we chose the ice cream design for Rimo. The front part can be moved to accommodate different phone thicknesses. The base is wrapped in fabric to reduce the coldness of plastic and metal. The bottom is made of rubber to protect against collisions. When Rimo rotates, the bottom rubber part remains stationary, while the base and the ice cream on top rotate.

The front part can be moved to accommodate different phone thicknesses

As we started the detailed design, we quickly encountered a challenge. The original design placed the power switch and charging port on the base, connected to the main circuit board. However, HatchDuo's ice cream design placed the button and power indicator at the front of the ice cream, far from the battery and motor. Therefore, we needed to design a "sister circuit board" to handle the button and power indicator. While this wasn't a major issue, it would simply require extending the power cable from the main circuit board's battery to the sister board's switch and then back to the main circuit board's motor.

Later, HatchDuo suggested that the switch was unnecessary and that Rimo should turn on automatically when a phone was inserted. They asked if we could achieve this without a mechanical switch. After some thought, we realized it was indeed possible, similar to what I had taught in my previous lab experiments as a teaching assistant. We could use an infrared photodetector to detect changes in the light from an infrared LED to determine if a phone was inserted. An infrared LED and photodetector could be installed on the sister circuit board. The infrared light emitted by the LED would bounce off the phone screen and be received by the photodetector. When no phone was inserted, the infrared light would bounce off the phone holder and return, resulting in a weaker signal due to the longer distance. Through experimentation, we found that this approach was feasible. However, this design created a new problem: the battery drained very quickly. Since the infrared light needed to be constantly on to detect the presence of a phone, there was no way to turn it off, leading to continuous battery consumption. If we reverted to a button design, it would delay the entire project and render the past month of experiments and research useless.

We spent a lot of time at home pondering how to achieve a buttonless design without using infrared light. One day, I was struck by an idea while using the restroom. I noticed a faint red light inside the machine above the urinal. We all know that this red light is used to sense when someone approaches or leaves to trigger the flush. However, what I hadn't noticed before was that the red light on the urinal was actually flashing. This flashing red light gave us an idea: the solution to saving power was just to make Rimo's infrared light flash! In the end, we set Rimo to flash for 0.01 seconds per second, meaning it only used 0.01 seconds of infrared light per second, increasing standby time by 100 times. Of course, we could also set it to flash every two or three seconds, increasing standby time by 200-300 times. However, the downside of this approach was that it would take up to two or three seconds for Rimo to power on after a phone was inserted. We felt that one second was still acceptable for most people, so we decided to flash it once per second, achieving the buttonless design.

The green parts represent electronic components; the distance between them posed a major challenge