My final project

Initial thoughts - Week 1

A few years ago, I built a Beerpong table that is illuminated with LEDs and changes color when the ball ticks. The whole thing was more of a coincidence, however, because I didn't program or install any controllers or anything similar, but instead used the music function of the party LEDs. Since then, I've wanted to make the whole thing better and more portable and smaller. So for the final project, I'm concentrating on the hit surface, which has space for ten cups and can be placed modularly on any table. The cups are to be illuminated from below, which is why there are placeholders on the top board, which will probably be cast from semi-transparent Epoyid resin later on. Below the top board, I would like to attach vibration sensors to try to detect when a cup is hit and then play various light animations. I might want to use a display to motivate or demotivate the team behind their cups and add different features later on.
All in all, it will be a triangular structure made of two wooden boards and side panels with a cavity that I want to use for light installations and the installation of the electronics. This would allow us to play Beerpong in style at Fab25 and afterwards, of course.

Computer Aided Design - Week 2

Because I would otherwise find it odd to only show content about file compression in the Computer Aided Design Week tab, most of the work this week can be found there. I just want to give you a quick update here in the form of a video that I created in Fusion 360 and edited with kdenlive. It shows the design process and, at the end, an animation that is intended to illustrate a successful throw in beer pong. The choppy course of the ball is not really intentional. I have to simulate the ball's trajectory using a sequence of different positions, so this is a movement sampled in this way, and I would have had to invest a lot of time in making it look smooth for the eye. Unfortunately, I didn't have the time at the moment - perhaps there will be an update here in the future. Grab something to eat and make sure you have enough to drink and enjoy the next eighteen seconds. This is the current status of my final project after week 2.

Computer Controlled Machining - Week 7

As described in my assignment for the corresponding week, I mounted my own milling cutters on the machine. To work as efficiently as possible and avoid duplicating the work, I milled the upper and lower plates for the prototype of my final project in addition to the parts for this week. I used a 12 mm plate for this, and in the Fusion setup I first machined the 2D contours with the 8 mm roughing cutter and then finished them with 6 mm. To be on the safe side, I installed retaining bars in each case, which I later cleanly milled away with the hand-held router. I then slightly rounded the edges with another cutter in the same way, with the following result.


By manufacturing the parts this week, I hope to be able to better estimate how many LEDs I'll need later, which will allow me to dimension my mobile power supply and other components on the PCB based on that. It also gives me the opportunity to use sensors to test my ability to detect hits in cups.

Input Devices - Week 9

This week, I used the group assignment to validate my proposed measurement principle. Ideally, I would like to implement hit detection based on vibrations. To potentially detect the cup being hit, I need to be able to triangulate between measurement signals. To do this, I need to accommodate at least three sensors, which is why I marked three points on the bottom plate that would be suitable for mounting. I attached the sensors to these points using double-sided tape and connected them to the oscilloscope as shown in the group assignment. Then I turned the setup over and placed the cups on top to make test throws. I didn't use the actual top plate for this because of the holes.


True to my theory, a throw onto the rim of the cup should result in a stronger vibration than hitting the cups filled with water for the test. This was also the case in practice. There is a problem with throws that hit the water without touching the cup; these did not show any significant deflection on the oscilloscope that could be analyzed later. So, my system currently seems to be blind to these types of throws. Another theory, which has been confirmed in practice, is that the vibration frequency is dampened and thus slowed down when the ball hits the cup, i.e., when it comes into contact with the water. Here are some measurements. Unfortunately, the three identical sensors have different sensitivities; please note the box widths below for the measured values.


The package from Digikey, which with any luck will reach me before the end of this century, contains vibration sensors that deliver an output voltage of up to 80 V. The sensors used for the tests delivered values ​​of up to 5 V, depending on the vibration, so I hope this will increase the sensitivity and allow me to improve the results. I'm also considering using thinner wood and mounting it in a way that allows it to move slightly, if possible, to better transmit the vibrations to the sensors. I also want to test light sensors as a redundancy, since the cups will later be placed on translucent material and ideally also need to be illuminated from below. To have this option, I bought some transparent cups a few weeks ago. That's all the testing for now.

In addition to the pure amplitude of the signals, I want to use frequency analysis to draw more precise conclusions about the type of hit. To do this, I use the Fast Fourier Transform (FFT) to decompose the time signal into its frequency components. Different types of hits—such as a ball hitting the table or directly into the water—hopefully produce characteristic frequency patterns. Edge hits might exhibit higher frequency components, while a ball falling into the water should cause a more low-frequency oscillation. By analyzing the frequency spectrum, I can define thresholds for different hit types and thus improve detection accuracy. The FFT decomposes the complex signal into its individual frequency components and shows which frequencies are contained in the signal and how strongly they are represented. The result is a frequency spectrum—a kind of "fingerprint" of the hit. The combination of amplitude and frequency analysis offers me, in the best case, a more robust differentiation option than measuring the amplitude alone.

Further work - Week 10

Since I had more or less finalized my measurement setup, I tested the new sensors after they arrived. At the same time, I tested the oscilloscope's Fast Fourier function. Given the results shown below, I may have to look for other solutions or keep the Fast Fourier analysis very specific. Another source of error that I could actually get is the sampling rate, which in my case will be significantly lower than 20,000 samples per second. In its current form, the signal might not be informative as a supplement, which is probably due to its brevity. There's both a short-term FFT and the option to evaluate the zero-crossing rate, but I can't test either of these with the oscilloscope—so I'll have to postpone further work on this. I'm confident I can solve this, but I'm sure I'll have to spend a lot of time and do a lot of testing.

Midterm - Week 12

This week, we were tasked with further planning our final, listing and planning outstanding work. I've compiled the entire process in a table format for your convenience.