communicate between Micrologix1400 plc and PIC micro controller

[ANISETY]

Dear All,
Can any one give me the idea how to communicate Micrologix 1400 PLC and any PIC Micro controller...
My idea is to read the temperature in a plc(Micrologix 1400) and displai it in a big SEVEN segment LED display using PIC microcontroller..

IF any one working on this type of projects .... please help me..

 

[nettogrisen]

While i don't understand why you don't just control the 7-segment display with the PLC, the fastest would be to set up modbusRTU commonication between the PLC and the PIC.
I'm not familier with the PIC, but I know that there are several modbus libraries for AVR. I suspect that the same goes for PIC.

 

[ANISETY]

thank you jasper.

thank you jasper...... for ur kind reply..
Can please send me any of the project so that i can work it out....
I dont have any limitatation about the micro controller...... just i want to communicate 1400 plc with micro controller to log the data from particular location for example F8:0...
Please help..

 

[Ken Roach]

In your first post you were trying to communicate with the MicroLogix so that you could run a 7-segment display with your microcontroller.

Now you want to "log data" with your microcontroller.

What exactly are you trying to do, and why are you trying to build the control system starting with a microcontroller ? There are many off-the-shelf commerical solutions for both of those functions.

 

[danatomega]

This is a link to Microchip PIC 16F87X Modbus RTU Projects:
http://www.modbus.pl/node/18

 

[ANISETY]

In your first post you were trying to communicate with the MicroLogix so that you could run a 7-segment display with your microcontroller.

Now you want to "log data" with your microcontroller.

What exactly are you trying to do, and why are you trying to build the control system starting with a microcontroller ? There are many off-the-shelf commerical solutions for both of those functions.

Hi....Ken
data logging means nothing but i want read the temperature value from the plc 1400 from particular location (say f8:0) and display it in a 7 segment display by using microcontroller.....

Sorry if iam hesitating you...

Iam new.. and i want some idea(Basics)...about the communication between plc and micro controller...

 

[Ken Roach]

"Data logging" suggests that you will be storing many samples of the data value. This is very different from displaying the current value.

Because the MicroLogix 1400 supports Modbus RTU protocol on the serial port, that is the simplest and best documented serial protocol to use. There are Modbus RTU libraries for almost all popular microcontrollers.

Is this a project for a school class, or are you developing a device for mass production ? There are many LED displays that can accept serial communications directly, which will save you a very large amount of time.

 

[ANISETY]

thanks Ken for ur valuble answer... its only a project for my class... can u give any sample codes for communicating with plc...

 

[Ken Roach]

You need to search for code libraries that implements Modbus RTU protocol for your particular microcontroller.

Dan gave one link above, and there are certainly more that you can find with Google.

 

[ANISETY]

yes i got that... but in plc there are several data locations....F8:0, N9;0, B3:0..... how can i specify in my microcontroller program about address location of the plc from the point i want the data.... any sample...plsss

 

[nettogrisen]

You have to map the modbus registers to point to the right memory registers in the PLC using RsLogix500. Eg. N7:0

Here's an example:

http://www.mesta-automation.com/modbus-configuration-example-for-an-allen-bradley-micrologix-1400/

You want the part on Modbus RTU slave

You can't map floating point though, so you have to move the values to integers, but that shuld be a trivial matter.

 

[ANISETY]

Thank you Jesper......
Iam looking for this kind of answer..... thanks alot

 

[shooter]

as it is for class:
you use two outputs from PLC, one for clock and one for data, you can use any type transistor is a little faster then a relay but still possible.
Use some resistors when having 24 V transistor PLC, to get the voltage down to PIC 3.3 or 5 Volt.
Now make yourself a communication i would use I2C as docs are fine and drivers for pic are existing.
on the pic you will need two inputs to get the signals. With relais it will take some seconds to get the needed info.
dont mess with floating reals, just use a INT or WORD the dot will divide it by 10 if needed.

It is also possible with some shift registers.