need advice on PLC project


Thread Starter


I'm a final year engg student of elex and instrumentation.. My major project is Weather monitoring system using PLC.. It was just a topic i chose with no prior knowledge of what the project is supposed to do..

As i worked upon, i planned the sequence of the project.. i decided three major parameters to be sensed: temperature, atm pressure and humidity.. but i stopped at 'PLC'.. i'm not aware if it takes analog inputs and can perform a check that whether the input lies in a specified range or not? For eg, i've been suggested that the plc program should be able to indicate somehow when temperature exceeds 45'Celcius.. Is this possible through PLC?

Moreover i'd like to know is this project good enough for final year of engg?

Bruce Durdle

As a start, google "PLC analog" and see what you get - this will give you an indication of what is out there.

Sure this sounds like a great project, and yes this can be easily accomplished with a PLC. I would suggest checking out the AC500-eCo from ABB. It is a small controller that comes with built in analog and uses an IEC61131-3 compliant programming tool that is based on CoDeSys (3S software). 3S software is platform independent and contains 5 different programming languages that are used in most controllers today. Very reasonably priced.
The main hardware you will need consists of the following:

PLC including minimum 3 x Analog Inputs (for your sensors) and almost all units will offer some Digital Inputs and Outputs as standard, Sensors (for Temp, Pressure and Humidity). As this will be a low-budget solution, I suggest you look at Micro PLCs which usually come with free programming software and inexpensive connection cables. For the sensors, to make things easier you should try and purchase sensors pre-calibrated to suit your desired range.

You should also understand why the Calibration is required and this should be in your documentation to prove that you have done the necessary research. Your software in the PLC would have a setpoint above which you could activate a digital input which may operate an alarm (lamp, buzzer, etc.) You may wish to include a pushbutton connected to the Digital Input to 'mute' the buzzer and/or reset the alarm.

The most important thing is that you understand the system and make informed decisions yourself.


Tom Chubb
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