I am doing a project based on PLC. I am using OMRON PLC CP1E-E20SDR-A. Now, I want to use a soil moisture sensor but the sensor is in analog so i have to use an adruino to scale it so that it can be read by the PLC. However, I have no idea how to connect the adruino to PLC
Show as much detail as you can about the products you are using.
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .
What inputs do you have available on that model PLC, analog, digital, rs232, 0 -10V or 4 - 20mA?
What is the sensor, what is its output signal?
Can you tell us your electronics, programming, arduino, hardware experience?
A PLC can do scaling as well.
I suspect you have the base model PLC and it only has digital I/O, you may need to get an extenstion module with an ADC input.
Thanks.. Tom... 
soon960122:
I am doing a project based on PLC. I am using OMRON PLC CP1E-E20SDR-A. Now, I want to use a soil moisture sensor but the sensor is in analog so i have to use an adruino to scale it so that it can be read by the PLC. However, I have no idea how to connect the adruino to PLC
Will the Arduino be measuring moisture and output to the PLC if it is >= some value?
Can you count pulses with the PLC? Arduino could pulse a digital pin to send a count.
OMRON PLC CP1E-E20SDR-A
12 inputs 8 outputs
Digital I/O only
Not expandable
No built-in RS-232C port
No built-in RS-485 port
Option Board cannot be mounted
I'm planning to do a smart fertigation system with some sensors such as
IR sensor (digital)
Soil Moisture sensor (analog)
Temperature sensor (analog)
and so on.
Some of it is in analog.
Is there another way to interface PLC with the arduino?
Hi,
It sounds like you don't have a PLC capable of doing what you need.
I would think you would have a display of some sort as well.
What version of the CP1E do you have?
There are expansion boards available, but only on 1.2 Ver models or later.
Tom....
"Is there another way to interface PLC with the arduino?"
Once again, can you count pulses with the PLC?
What you want to do does not affect the answer to that question.
The data sheet indicates that there are six inputs with high-speed counters (10KHz maximum), so you could pulse an output pin with a varying frequency dependent on the analog value. Another option, if the PLC programming will allow it, is to use two output pins, one to indicate an analog value is being sent, and another to generate a specific number of pulses proportional to the analog value.
Does not appear that you can directly connect an arduino output pin to the input pin of the PLC, the input specs indicate you need a minimum of 17v on an input to turn it ON.
Another possibility is to do all the processing in the arduino, and only output digital signals to the PLC.
A question - why are you using an arduino and a PLC, instead of an arduino with a relay board?
Arduino can open a transistor to deliver 24VDC.