Controlling water valves and sensing temperatures with a PC.?

Question

Hello all
Does anybody know of some hardware and/or software that will let me control a number of liquid valves and sense temperatures with probes away from the PC. I'm sure that there must be something out there somewhere???
I've done the usuall googleing but with no luck.
Thanks In Advance Rich

Hello all
Does anybody know of some hardware and/or software that will let me control a number of liquid valves and sense temperatures with probes away from the PC. I'm sure that there must be something out there somewhere???
I've done the usuall googleing but with no luck.
Thanks In Advance Rich

All I need to do is open and close a valve(6inch) allowing liquid to be added into tank (computer controlled) and a tank under that tank with water in it that is fed by a hot water supply that is running past it. Valves can divert hot water into the lower tank when it cools to say 35c to up the temp to 37c again. This keeps the upper tank at 37c. Maybe theres a lego machines software out there???

This must be achivable with a simple program that has allready been written?

TA

Answer 1

Rather than get all complicated with control valves and switches, why don't you just add a heating element and temp controller to the top tank? This will have the advantage of having zero moving parts and would be more reliable.

However if you really want to go the valvle route you need to start with the design of the pipe system and understand exactly how it is going to operate before you try to automate it. For example these valves you want to control, are they going to be electrically operated or pneumatic. Will the valves need to modulate to control flow or will full on or full off flow control do? Same for temp sensing, do you need to read temperature into your controller or can you use a temp switch which provides ON/Off input to the control system

These simple question will help determine your control strategy and minimized the complexity of the controller and system.


Having a PC control a critical system is not recommended. I would recommend a small micro/nano sized PLC (Programmable Logic Controller) which has limited Input/Ouput capability but has the advantage of being robust and stand alone. Analog input are available for these small PLC's and some micro PLC's have the ability to add additional function modules (Temperature input, Digital Output, Digital Inputs)

Some brands of micro PLC's are Keyence, GeFanuc, Unitronics.

The Unitronics brand has teh advantage of providing some free software which allows communication between the PLC and a PC for exchange of information and data logging directly in to a spreadsheet.

Answer 2

Although I'm sure there are 'off the shelf' applications for this type of thing, it does tend to be a specialised operation. Especially if you have to assign specifics to the ambient temperature of the area you are trying to control.

Much better would be a high level language program that, once set up on your computer would take just a little bit of effort to master the adjustments you'd want to make.

High level language compilers will allow things like:-

If temp is <>(greater or less than) x - then switch ABC
So a typical line of high level language code would read:-

if temp is <> x then switch A = 30 degrees etc

Go here for a list of consultant computer programmers:-

http://www.freeindex.co.uk/categories/Computers_and_Internet/Computer_Services/Computer_Programming/

Answer 3

You could use a PLC (Programmable Logic Controller) if the temperature probes are not linked to the control valves, but these are relatively expensive and difficult to set up if you have no experience with them.
However, if the valve will be opened or closed to try and control the temperature probe, you would be better off with a stand alone PID temperature controller. We use Eurotherm controllers for such applications. Please see the link below.

http://www.eurotherm.co.uk/

The controllers we have used are not capable of being connected to a PC but the new generations may be.

Answer 4

You can use PLC (Programmable Logic Controller) for that.
It's basically a microprocessor (computer) controlled system which is programmed using a programming panel or keyboard. PlC's are typically used to control the operating sequence of machines, production lines and industrial processes.

Answer 5

You can try looking up PLC -- that is, process line controller -- for a starting point.

At my school, where I'm studying building systems engineering technology, they have these Lab-Volt process trainers, which do the sort of thing you're looking for:
http://www.labvolt.com/display_left.cfm?ProductID=300&TopicID=80&view=topics