Greenhouse controlled by PLC

Hello friends

I need to monitor and control a greenhouse 8x30 meters, 5 height.
The first stage is to install 4 temperature sensors, 4 humidity sensors, 1 air flow, just to monitor this variables (installed at different points), in the second stage I would control some valves and pumps.

The main control would be at 5m from the greenhouse.

My expertise is Allen Bradley PLC, what PLC and sensors do you recommend?
Would be wired o wireless sensors?

I think that we need an HMI to monitor and control the greenhouse, or maybe a PC with Labview could do this task, also this PC could save some data.


Thanks in advance

From your brief description it seems that you will need a minimum of nine Analog Inputs: have you thought about how are you going to "control" the system outputs which will "keep" the data arriving via the said Analog Inputs within user defined "limits"?
If you could go "wired" (5m is a short "hop") choose it; wireless will open up a huge "can-of-worms"....
As for CPU/HMI brands, there are plenty reputable ones out there...
If you are familiar with Allen-Bradley automation there are two platforms I would consider: the MicroLogix 1100 or the Micro850 one.
Unfortunately, since you will need a "considerable" number of Analog Input points, you will need to add at least one expansion (or Plug-In for the Micro850) Analog Input module to either chosen platform.
For the HMI, the PanelView Component platform will suffice for either chosen CPU since they both support Ethernet connectivity.
MicroLogix user software is not free, however, it has Rockwell Automation "mainstream" functionality.
Micro850 user software, CCW (Connected Components Wokbench) is free and it could develop both the CPU application and the PanelView Component one.
If a MicroLogix CPU is chosen, the PanelView Component HMI application could be developed via web browser such as IE.
http://ab.rockwellautomation.com/Programmable-Controllers/MicroLogix-1100#/tab2
http://ab.rockwellautomation.com/IO/Chassis-Based/1762-MicroLogix-Expansion-IO

http://ab.rockwellautomation.com/Programmable-Controllers/Micro850
http://ab.rockwellautomation.com/Programmable-Controllers/Micro800-Plugin-Modules

http://ab.rockwellautomation.com/Graphic-Terminals/2711C-PanelView-Component-Terminals

Hello



Monitoring sensors is the first stage.

The second stage is to control a pump, some valves to keep the temperature and humidity.




I would like to use Micrologix, because I can connect to Labview through Ethernet.

Do you know what kind of sensors could I use?

affect the distance?

what cable should I use? or should be wireless?

Thanks

I am not quite familiar with ambient environment sensors; I have been exclusively using instrumentation of the process kind.
Any reputable brand analog type will do; the only compliance will need to be addressed will be with the chosen Analog Input module electrical ratings.
Analog signals could be routed over long distances (hundreds of meters) and they are very accurate; if choosing Analog Current instrumentation/PLC modules your system will also be very resilient to any electrical "noise" interferences.
You could use wireless, however, this will exponentially increase your costs since you will need to create a communications inteface between the sensors and the CPU controller.

For temperature sensors use an RTD - far more accurate and reliable at lower temperatures and no need for special extension cable.
In Australia we can buy special air sensing RTDs - there are holes in the bottom of the tube to allow air to flow over the RTD module directly.
Put these straight into an RTD card and get away from transmitters - lot less trouble and less expensive.
Humidity sensors are problematical at the best of times. They normally need to be calibrated from time to tome too. I bought these and they are not too bad - work pretty well.
http://www.cometsystem.cz/products/...oor-indoor-probe-with-4-20ma-output/reg-T3110
By the way, I am also using a high pressure fogger for humidity control in a shade house, that way there are no water droplets on leaves as with misting heads and therefore less fungal problems.
Automatic watering is almost impossible as you always miss something - usually a valuable or hard to obtain plant.
I am using and Omron CJ2 PLC with wireless Ethernet to a computer in the house and a SCADA package running on the computer. That way I can trend my values and also change set points in the PLC from the computer.

RTD is best option here as they are accurate.
buy one analog input, and use a few control relais to switch between the sensors.
have 4 sensors with a small sock hanging just above a watercup (it will give you wetbulb temp) and this is a good indication (and far more accurate as any other sensor) for the humidity.
even for the airflow you can use a RTD (give two of them a little more current and mount one in open air and the other on a metal plate so it can dissipate the heat) the diff in temperature is indication of airspeed.
wired sensors are accurate and need no batteries.
This is a solution with only one type of sensors. cheap but reliable