This is the 15th collaborative clock project that Dave Bruckenstein and I
have completed. It uses a "decoder" window that moves to
reveal hours and minutes when triggered. At rest the
decoder stays at the top showing meaningless shapes.
When the RFID tag is placed right in front of the base the
clock will show the time by moving the decoder first to the
hour and then to the minutes (in 5 minute increments).
Watch the video below to see how this works. The
Cryptic code was provided by Charles (AKA cfb70), see his
Cryptic Calendar at
https://www.instructables.com/Cryptic-Calendar
Shown above is the time: 5:05
I machined the carriage that moves the decoder from 1/4"
aluminum - the decoder is 1/8" white acrylic. On the
left you can see the "home" switch that allows the mechanism
to calibrate it's position each time it moves. It
always starts by moving up to stop on that switch, then down
to the hour + minute positions. The motorized
ball screw is driven by a stepper motor inside the case.
On the back of the case are 2 buttons to allow you to set the
hours and minutes as you can see in the video below.
Inside the case are all the electronics. I hand wired
the circuit circuit board that controls everything. It
includes a real time clock chip powered by a coin battery so
the clock can be unplugged for months and never lose time.
I took apart the keyfob RFID tag and made a clear acrylic
housing for it. It's neat to see the tiny black dot
that is the chip that holds the tag code, and the circle is
actually a round antenna made from concentric rings of
thin wire.
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