which is right plc

Hi all ,

I am a student working on my first PLC project . My project is to automate a mobile water purifier .the water purifier consist of 2 tanks.One tank serves as the resrvior and other for storing pure water . the water is purified by ozone generated from an ozone generator . Hence water is pumped from the reservior using a pump , this water is mixed with ozone and mixed well using an ozone pump and then to tank 2 . the water from tank2 is obtained as output through a filter .


I have to use 3 sensors . Flow sensor , ph sensor and a dissolved oxygen content sensor .

I am planning to control the flow by using an electronic control valve .

so i have 3 analog inputs and an analog output . Inaddition i have to set up an HMI as well . Which allen bradley plc is the one that i should use ??

I think almost every answer will be different to your question. A couple of years ago I designed an Ion Exchange system to remove contaminates from water. I used an SLC 500/4...why? For two reasons first I had a rack that had a SLC 500/3 processor. When I decided I needed more communication between that equipment and the equipment feeding it I upgraded to a SLC 500/4. This allowed me to create a DH+ network and to share more process info between processors.

Many would advocate an Ethernet capable PLC. If you are planning for not only your purification system but also for networking the purification systems to talk with other waste processing equipment then Ethernet is the way to go.

However if this system is to be used in the poorest part of Africa with no maintenance techs in sight you probably want to look at reliability. (I have no opinion as to which is the most reliable. I've had to replace components that have died or fried on SLCs, and Micrologix. The one (model) that always seems to work at my plant are the contrologix PLCs but they are newer then most of the SLCs).

If it is to get dirty water clean for the lowest cost possible then there is a whole new direction to focus on - and Allen Bradley might then not be the solution.

There is no 'right' one, with your system as described...google 'plc' and pick one.

But if you're a student, then what does the exercise require? What resources do you have available? What have you been trained on?

I would go with the ABB eCo series PLC maybe a PM556. this is a powerful inexpensive PLC and the software is free.