Wednesday, May 10, 2017

Certamen machine

My kids are involved in a Classics oriented quiz game called Certamen at school. These involve teams and buttons and a machine that determines the order in which buttons were pressed. Surprisingly, these machines seem to cost a ridiculous $500 and up, despite seeming to be quite a simple thing: 12 buttons, display which order the buttons are pressed in, lock out fellow team members once one member of a team has pressed it.

So I offered my kids' school to design and build one for them as a fun summer project for me and an opportunity for my kids to learn to solder. I ordered about $60 of parts, mostly from Aliexpress, centered on an Arduino Mega (I haven't done any Arduino-based programming, but I've used the Arduino toolchain with an ESP8266 before). The parts have started to come in, including the Mega, so I've started writing some code and prototyping. According to my oscilloscope, the quick and dirty polling code I have gets a worst-case detection speed of 0.1 milliseconds, which should be good enough for a quiz game. (I continue to be grateful to the Austin guy who gave had an oscilloscope for sale for $50 on Craigslist, but when I wanted to buy it, gave it to me for free because he liked the sorts of things I was going to use it for.)

I am a bit nervous about signal problems over the three five-meter CAT6 cables (the most expensive single parts of the project) from the control box to the buttons, but I ordered some capacitors for noise suppression, and once my RJ45 jacks come in, I can do some testing.


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