So I’m back from a week travelling across the western half of Canada with the lovely and talented Mrs. Zheng3 and her parents. We now return you to your regular schedule of intermittent blog posts.
The trip began in Vancouver where I enjoyed the singular pleasure of spending a couple of hours meeting with the Pinshape team at their mothership. We discussed some of the more pressing questions facing 3D printing designers today, including but not limited to where one might obtain the best dim sum in BC’s fairest city.
Great bunch of folks, these Pinshapers. Sharp as tacks and friendly to boot. Take a look at their site and you’ll find a nicely-curated selection of models.
Robber Rex (a favorite at Pinshape) managed to visit the Vancouver Public Library, which has been cunningly constructed to resemble the Roman Colosseum.
The Saskatoon train station is as bleak an outpost as you’ll find, but still a welcome diversion for a constipated Parasaurolophus who never quite got the hang of pooping in a cramped train toilet.
The long train ride from Vancouver to Winnipeg, made longer by frequent sidesteppings to allow freight trains to pass, allows for much contemplation and idea generation and idle sketching upon napkins, and by the time I returned home I was more than ready to jump into the next project: RGB color sensing with Arduino.
There are, presumably, roll-your-own RGB sensors cobbled from disposable contact lenses, photoresistors, and Oreo cream, but at some point one must accept that expedience takes priority over molecular-level knowledge of a process and you just can’t be mining your own beryllium all the time. So to Adafruit we go, and earlier this week a TCS34725 RGB color sensor arrived on the doorstep of Zheng Labs.
The Adafruit tutorial is remarkably easy to follow and we were up and running in less time than it took to print George Timmermans’ handy Arduino and half-sized breadboard caddy, including the time required to solder the sensor to some headers with long-unused and filthy soldering iron tips.
I’d link to the caddy directly except that WordPress is throwing some weird Unicode error and it’s too early in the morning to troubleshoot HTML errors. It’s on Thingiverse.
This little board contains a white LED that burns with the intensity of a thousand suns, so you may want to wire it to ground and turn it off while you’re experimentin’ or you’ll be seeing afterimages of your workspace for hours.
The book in the background is fellow Wisconsinite Jordan Ellenberg’s How Not To Be Wrong
, which, 50 pages in, is so far a fun read. Any book that starts off with a humorous telling of statistical analysis of bullet holes in WWII airplane fuselages is going to be good.
Our engineering team ran into a little bit of trouble trying to get Unity3D to talk to the Arduino and settled for a temporary solution using Python code direcly cannibalized from 2012’s Etchasketchulator project:
ser = serial.Serial('/dev/tty.usbserial-A700fjTr', 9600)
valueIn=ser.read(50) #read the first 50 characters that the arduino is sending
That /dev/tty.usbserial-A700fjTr serial address is the currently free USB port on my MBP: if you’re using a PC you’ll likely replace that string with something that looks more like COM4. Check your Arduino IDE to see which port to use.
Looks like I need to make the serial communication a little more elegant; it’s timing out, throwing errors, is badly formatted, and generally a mess. But let us not let the perfect be the enemy of the good. Iterate now, fix later.
I used a couple of ball pit balls as test objects. In the interest of presenting properly-formatted data let’s go direct to the Arduino serial monitor for the output:
Offscreen I’m waving a red ball over the sensor and, wonder of wonders, the red values change over time.
Next step: communicating with a passel of these RGB sensors. This should be a challenge, since each one has an identical address and as far as I know they can’t be changed in hardware. Getting ready to hop on the I2C bus.
I’ll clean up the serial communication by next time, promise. And calibration. Gotta do some pre-read calibration of the sensors for ambient light levels, too.
Note to self: buy new soldering iron tips before we go down this road. #staytuned.