called Python. I’ve done a fair amount of Python
programming and I find it great for small projects.
There are extensions for the Pi that allow control of the
programmable I/O pins. The Pi also has a good notion of
time of day, so behavior could be tailored to the library’s
hours. That might avoid false triggering if there is a cleaning
crew or a cat around.
The most important piece, though, is the motion
sensor. I found a nice one on the AdaFruit website for only
about $10 at the time of this writing. You can see it at
https://www.adafruit.com/product/189. The description
claims that it might work on zombies too, but they don’t
guarantee it. (Too bad.)
It has adjustable delay and sensitivity, and runs on a
wide voltage range that includes the 5V supply available on
the Pi.
The sensing voltage could easily be detected on one
of the I/O pins and conditioned in software, if necessary.
Then, a small state machine could be written that would
take the time of day, state of the train, and frequency of
hits into account. It could extend a timed run interval, for
example.
While it’s possible to do some amount of this with
analog circuitry (and it would certainly be a fun challenge),
I think that software is your friend here and will make for a
more satisfying and flexible outcome. NV
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12 March 2018
