Originally Posted by malador
I don't think i know what you mean by microcontroller. I use that term for small PLCs. I don't think it's fair to say that PLCs are restrictive. Can you give an example? I use a plc because i understand the logic, and there are some great inexpensive options out there.
Sorry, I mean microcontroller as in the likes of Arduino (I realise that a PLC is a microcontroller
), I'm not trying to argue that nobody should be using a PLC for homebrewing but I want to understand the benifits/restrictions of using them (both for DIY use and industrial). The biggest benifit (and kind of the only definitive one I could find from the internet) was that PLCs are so common place now and built around a language that those maintaning the plants inherently understand due to its link to physical relay logic that it is best suited for the specific situation. For DIY/homebrewing I just don't see that benifit transfering so that anyone that does not have a PLC background would benifit from using a PLC.
What I meant by restrictive was, (hardware) for IO each point is dedicated to a digital input or a digital output or an analogue input... which I would see ending up with spare IO which could mean you had to buy more IO blocks than if you could switch between IO types. Another question is what type of temperature sensors can you use?
(software, and I am likely completely wrong here
) from the small amount of ladder logic I have seen it looked like mostly "if" type arangments. I guess this is not an issue for the core function of the PLC which is basically "if something happens do something about it", but what I have seen is if you want to add a touchscreen or something you need to purchase a compatable one that the "screen" is controlled by itself and is only sending requests to do stuff to the PLC.
I guess my question would be answered with the answer to another question, If I want to build a controller that will control the following, what would it cost:
8 actuated valves
5 temperature inputs
4 PWM outputs (heat elements / pumps)
1 flowrate inputs
1 touchscreen HMI
Both of these should be able to be done either with an Arduino or PLC, but what would the cost be?
For Arduino I would estimate for the controls side only, i.e. not including the actual valves, sensors, controlled equipment (roughly):
Controller - $50 (Arduino Due)
8 Digital outputs (valves) - $30 (relay board)
5 Digital inputs (temp) - $10 (misc costs)
1 Digital inputs (flow) - $10 (misc costs)
4 PWM outputs (heat elements / pumps) - $10 (misc costs)
1 amount of flowrate inputs - $10 (misc costs)
1 touchscreen HMI - $40 (3.2" touchscreen - small I know
Total = $160