You say "Programmable Logic", add one more word, "Controller" >> PLC ,=20
and your application points to that. There are numerous out there, you=20
don't say what country you are in, there are numerous manufacturers and=20
models out there. Many are heavy duty industrial quality, UL, CE, and=20
other approvals. Allen Bradley Modicon is probably the most popular.=20
Most of the auto manufacturers use them to run very complicated=20
machines, but there are small units available. The PLC was the=20
replacement for relay logic, and the relay ladder diagram programming,=20
understandable by many trade electricians is still used today. Some have=20
a high level language like Basic available to handle analog and some=20
digital logic. I would think this would easiest to implement and=20
maintain. Just plug a laptop with their software, and can quickly change=20
things.

As a hobbyist, I have a standby generator that is managed by a PLC. This=20
includes starting, running, and shutting down on gasoline, propane, or=20
natural gas, switching under load between fuels depending what is=20
available. I use a TRI-PLC T100MD+ with MD-EXP4040 expansion I/O, and a=20
MD-HMI display keyboard. They have many other models available, some=20
much more basic, and some more advanced with Ethernet capability.
www.tri-plc.com

On 8/20/2010 1:01 PM, Denny Esterline wrote:
> Hi all,
> I have a project redesinging a little specialty industial controller.
> It was orginaly designed around about a half dozen relays, including
> some "Agastat" adjustable time delay relays. Unsurprisingly, some of
> these are being obsoleted and I've been asked to do the redesign. So I
> guess it's a good problem to have.
>
> Before it's suggested, yes, I _could_ handle it with a minor PIC, I
> may even protoype it with one anyway to verify the rest of the circuit
> and to quickly prove the logic. Due to some arcane rules, there's a
> ton of red tape to get a microprossesor based product installed at
> some of the end user sites. It's agravating, but that's the world I
> live in.
>
> So, I've done a cocktail napkin design and I figure I need about 30-40
> logic gates and four timers to duplicate all thier functions, of
> course, that's before the inevitable "feature creap" begins. Certainly
> in the realm of something that I can do with discreet parts, but I'm
> fairly sure it's time to look at some of the low end programmable
> logic parts.
>
> I've been chewing through the some of the apparent options, Xilinx,
> Altera, Atmel, and it's a little daunting. Not only do I need to get
> my arms around the development side of it, but I need to understand
> the production level tools as well. And picking a part that can handle
> my I/O count (13 and 12) and amount of logic is straitforward, until I
> notice some of the suppliers are obsoleting many of the parts I was
> initialy looking at. Even when some of the parts aren't being
> obsoleted, I'm seeing the dev tools being obsoleted, so I'm forced to
> wonder how much longer the parts will be around.
>
> I know that learning VHDL/Verilog will be neccesary at some point in
> my life, but here in the beginnning I'd prefer something simpler,
> especialy for such a simple application. Schematic capture is an
> option, as would be some type of logical expresion system (output X =3D
> input A AND input B OR input C)
>
> So, I'm seeking suggestions for a manufacturer / product family / dev
> tools / production tools, and any pointers to good reference material
> to shorten the learning curve would also be appreciated. My criteria
> in descending order of importance:
>
> Longevity of part (no obsolecence next week)
> Short learning curve
> Available dev tools
> Available production tools
> Complexity of support electronics
> Cost of production tools
> Cost of dev tools
> Cost of part
>
>
> You'll notice package size and power are not on the list, The
> equipment is line powered and controls a 1kW motor, a few more mA for
> the logic is fairly irrelevant. Part cost is last, because it's fairly
> low volume. At about 100 pcs / year, an expensive toolchain could
> easily cost more than the sum of the chips.
>
>
> Thanks
> -Denny
>   =20
--=20
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