Button Multiplexing, Redesign, and World-Travelling Packages

R2R Button implementation
In an effort to get as much out of as few pins as possible, we decided to try to make our 5 input buttons multiplex into one analog pin using an R-2R ladder Digital to Analog Converter circuit. Our initial implementation failed due to our momentary pushbuttons being single pull single throw switches (R-2R ladders need single pull double throw), however, we implemented a logic NOT gate chip that allows our pushbuttons to output 5V or GND to each input of the ladder. It works pretty nicely! By reading in the analog values for every possible combination of buttons, we saw that each voltage level was distinct and consistent, but not predictable with a formula. So, we put all those analog values in an array where the index of the array containing any particular value corresponds with the sequence of buttons pressed to obtain that value. It works well!



Chassis V3 In order to keep iterating on our physical chassis design, we redesigned such that we don’t use press-fit pegs anymore, but screws to hold on the motors. This should add stability to our wheels and keep everything secure! We also created a first design for the turret on top, including a spot for the high-power IR LEDs and two spots for visible light LEDs. This will give us a visible indicator that the tank is actually “firing” its laser. Package! We finally got our package from China! The darn thing got shipped to the wrong address in Provo, forwarded to Vernal, then shipped to Logan to a friend of Tyler’s. Both of us then drove up there to end the package’s tedious tour of Utah. Now we can finally get to verify our components and design PCBs to fit together with the exact parts we have. That will be our next primary focus.


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