"Ignoramus3322" wrote in message
...

On 2013-12-08, RogerN wrote:
snip

With a little additional programming, the pressure transducer information
could be used to get a little more run time at pressure. For example you
could measure the rate of pressure change when the compressor is running
but
no air is being used. The rate of change for the compressor can be
compared
to current rate of change of air usage. If air is being used as fast as
or
faster than what the compressor can keep up, you can turn in on before 90
PSI to give you more run time at pressure than you'd get waiting until 90
PSI to turn it on. Not sure that it would help you much but set points
that
vary with demand can give you more air.

I do not think that I can get more run time with that, and I
definitely do not see the benefit worth diong software, adding
computer etc.

i

About the run time, let me see if I can explain it better. For example,
let's say your sandblaster needs at least "X" psi to operate correctly. Now
if your sand blaster drains your tanks at 15 PSI per minute, and your
compressor adds 10 PSI per minute, then with the compressor on, you have a
loss of 5 PSI per minute. So if you could detect usage rate compressor
rate, and turn on the compressor at 120 PSI instead of 90 PSI, you get 6
minutes of usage at a loss of 5 PSI per minute, from 120 to 90 PSI. With
the compressor off, you get 2 minutes from 120 to 90 PSI.

I understand at this point the computer idea sounds too complicated /
expensive but that's kind of like your EMC experience. Sounded like too
much unfamiliar territory but you took it step by step, solved one problem
at a time, and ended up with a system that you can repair without high $$
parts and labor. And you added a 4th axis + knee?, that may not have even
been an option with the original control.

If anything like this ever seemed practical, options include a micro PLC
with analog input or something like an Arduino board, $30, has analog
inputs, free software, screw terminal add on for around $8. The 5V output
from the microcontroller can be used on AC or DC solid state relays to
control valves and/or magnetic contactors. So it's actually nothing like
using a PC and trying to interface to a compressor. Or perhaps some of you
scrap deals could have a controller in them that could be reprogrammed for
other tasks.

RogerN