Zworld Engineering (http://www.zworld.com) and Allen-Bradley have some low
cost simple controllers. Embedded industry always avoid a PC making
critical controlling decisions. The PC becomes little more that an
interface, passing commands off to the controller to carry out. You are
better of having a controller that can operate independent of a PC. At one
time this was my career: Zworld has a great learning package that includes
the controller, PC interface manuals etc. A great kit. I embarked on a
home thermostat, hot water controller, sprinkler system. I never finished
it, but I learned quite a bit.
----- Original Message -----
From: "Todd Robinson" <mtrob@penguix.com>
To: <slug@nks.net>
Sent: Monday, April 29, 2002 9:24 AM
Subject: RE: [SLUG] Control, I need CONTROL
> Radio Shack has a couple mini-handbooks that have a lot of simple sample
> circuits in them. A couple of transistor relay drivers and switches.
> You'll also need an 8 bit latch to catch and hold the value written to
> the parallel port. You'll have to work out all the loads backwards to
> make sure the relay can handle the solenoid, the transitor can drive the
> relay and that the transistor ciruit doesn't over draw the latch, but
> hey that's the fun of hardware. With that you would have 8 on/off
> devices. If that isn't enough, you could add a flip-flop and a couple
> And gates to make an addressing scheme where the 8th bit is a
> solenoid/address indicator and the lower 7 bits are solenoid or address
> indicators. Then you just clone the circuit with minor And gate changes
> for each address of 7 solenoids. If you do more than 2 or 3? of those,
> you'll need an 8 bit buffer so the latches don't over draw the parallel
> port. I would advise going and getting an add on printer board, they
> are cheap, just incase you blow up your printer interface.
>
> Todd
>
> > -----Original Message-----
> > From: slug@lists.nks.net [mailto:slug@lists.nks.net] On
> > Behalf Of Chuck Hast
> > Sent: Monday, April 29, 2002 8:00 AM
> > To: slug@nks.net
> > Subject: Re: [SLUG] Control, I need CONTROL
> >
> >
> > On Sunday 28 April 2002 13:40 L, you wrote:
> > > Here's one possible solution:
> > >
> > > http://www.sealevel.com/catalog/8007.htm
> > >
> > > This card will give you 32 relay (solenoid?) drivers. Other cards
> > > with different I/O specs are available.
> > >
> > > Sealevel provides Linux driver modules -- source. It's
> > very easy to
> > > use. Your program talks to the board (telling it which port to turn
> > > on/off) by opening a device file (/dev/dio?) and writing to
> > it as if
> > > it were a flat file using fseek(). You can use python or other
> > > scripting languages as long as they have the open() write() and
> > > fseek() commands or their equivalents.
> > >
> > > Now you have CONTROL!
> > > Ed.
> > >
> >
> > Ed, and all that replied, thank you. I now have some routes
> > to follow. I do have one question, this is my own system so I
> > an going to at least start it out on the cheap. (I need to do
> > some major sheckle scraping to purchase that card)
> >
> > I recall having seen control systems using the printer port
> > as the control port, which in turn talks to transistor
> > drivers and from there to relays. Does anyone have any ideas
> > on that one I can build up a lot of boards with transistors
> > and relays on them for what one of those boards will cost me,
> > later on as the system needs to be more reliable I will go to
> > the board right now I would like to build something that is
> > not quite so costly and though it may not be as trustworthy
> > it will work 90% of the time.
> >
> > I can visualize the controller part based on such devices as
> > 2n2222's and buffers with the 2n2222's driving small relays.
> >
> > --
> > Chuck Hast
> > KP4DJT
> > kp4djt@tampabay.rr.com
> > To paraphrase my flight instructor;
> > "the only dumb question is the one you DID NOT ask resulting
> > in my going out and having to identify your bits and pieces
> > in the midst of torn and twisted metal."
> >
> >
>
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