Hi Dragster,
Ok, one point at a time ...
Doing it via a PC program
Pro's and cons,
It means that you would have to make or find
some kind of 28 way interface.
Not as dificult as it sounds,
such an interface would have to take signals
from the LPT port in binary, and deliver
voltages to the 28 way lines.
It would also have to give a response for 'OK'
and for 'not OK'
The program would probably try each leg,
it would display on the screen the response,
probably very quickly, maybe within a second.
The program could probably then do a test firing
on those legs that were registering ok,
maybe a one second operation on each,
then a one second space?
that would be up to the person doing the program.
The results could be on screen,
and printed if required.
difficulty ?
Making or finding an interface wouldn't be very hard.
Getting the program to do what you want,
not easy, but there are loads of people doing that
sort of thing, theres plenty of help about.
How did i draw that ?
Its only drawn using 'Paint' or 'Pbrush' as its
called on older machines. Its quite a good program
hasn't got the special facilities of more
expensive ones, but its standard with windows.
For sending over the server connection i use 'save as'
and i save the BMP as a JPG, thats more economical
with kilo bites size.
Paint is standard with windows.
Complex ?
It looks more complex than it really is.
For instance, the bit that says:
'passes on the pulses unless its told not to'
Thats only a resistor and a diode!
But it has a function in the logic,
so it gets a box of its own.
And the bit that says:
'output if any leg refuses to go high'
an output in this case is a 'low'
when it should be a 'high'
again, only a few components.
There are complicated bits, there would be for
a circuit to do this, but nothing too bad.
LED readout from ten buttons
I dont think that would help you.
That gets a bit awkward counting over ten,
using carry, and zeroing at 28, that would have
to be arranged by the constructor
relays
You have mentioned relays several times,
and relays can do some things,
but i don't see how they would help for this.
It took me two years to find a workable and
practical circuit to use a relay as a bi-stable.
It took me a week to get a relay to operate as
a square wave oscillator. (12v)
I made a 10 c/s 50v rough spiky generator from a
relay to drive an old GPO bell, from 12v, that is
still working ok after 4 yrs.
But i dont see what you have in mind for relays.
Regards, John