my vacuum controller project

Well, almost done.  It's up and working now, and I had loads of fun in
the process.  To use the M100 as a controller, as I've mentioned I'm
using the BCR port to power a vacuum sensor, and take the readings.
Originally thought to use the printer STROBE signal as an output, but
that does not work.  I changed the plan to use the casette port relay
instead, and that works great.  I used an old modem cable to connect
to the cassette port, and to make the specific wiring I needed.  The
casette relay drives a signal to an external relay board that has a
relay capable of switching 120V 15A.  That relay sends power to the
vacuum pump.  My 555 circuit to convert DC voltage from the automotive
MAP sensor, to a frequency, worked well, however it is not linear.
So, I had to use a lookup table to correct the non linearity of the
sensor.

The coding was so fast and easy...I'm surprised I did it.  Usually I
have a lot more pain.  I had the M100 in the test set up, with a REX
installed with TSDOS.  I could compile assembly and directly load and
test the changes, which made for very fast iteration.  Overall the
software is simple.  I use function keys to vary the two setpoints up
and down.  The setpoints represent the vacuum at which the pump either
needs to switch on, or switch off.  In effect, they are the max and
min vacuum settings.    I simply loop quickly looking for either
inputs from the keyboard to adjust the settings, and make vacuum
readings, and decide what to do with the pump.

I've got the entire rig mounted in a wooded case that has 120V AC in,
vacuum in, and a relay controlled 120V outlet for the pump.

This is the first application that I had originally intended to be my
use for M100s - controllers.

I'm thinking of taking some photos of the entire system in use,
pulling vacuum against some composites I want to build.  If anyone is
interested, I'll post something simple.

regards, Steve