Drives&Controls & BACK TO BASICS n SPONSORED BY Despite cleverer drives, we still need PLCs Drives can increasingly take on some simple PLC functions, but for more complex automation there’s no substitute for a dedicated PLC, argues Carl Eely, ABB’s product manager for industrial automation. When automating simple motor-driven tasks, such as operating an automatic door, or raising and lowering a car park barrier, the logic required is often relatively simple and self-contained. There’s usually also little need to coordinate with other processes. The adaptive programming functions in a modern drive can allow you to automate these processes without having to buy, install and program a separate PLC. However, PLCs excel at more sophisticated automation tasks, or in complex systems where you need a single point of control. A drive will generally have a maximum of two PID loops, while a PLC can have upwards of 30 or 40, allowing it to monitor and control multiple systems and processes simultaneously. Consider the example of the car park barrier. If all you need is a single barrier to lift up and down, triggered by a timer or perhaps a sensor, then this can be automated using a drive with adaptive programming. However, if you have multiple barriers in different places and want them to communicate and/or coordinate with each other, that’s where things start getting complicated. Perhaps one barrier is stuck open or closed, or you need to raise all of the barriers to allow emergency service access. In these scenarios, it makes sense to have a single point of control – a PLC, from which you can remotely control all barriers simultaneously if needed. As well as providing more sophisticated control functions, a PLC can also communicate easily and securely with both local networks and higher networks – for instance, to connect to an SQL server or Scada system. The PLC can also accommodate more easily the integration of multiple other devices such as HMIs, sensors, actuators and even drives. In an increasingly data-driven world, a PLC is also the best way of not only getting data out of your process, but making sense of it. The PLC can be a focal point for data aggregation, allowing operators to control and monitor both at an individual device level, and at a big picture level. For more information, search for “ABB PLC automation” igus® Caswell Road Northampton NN4 7PW Tel 01604 677240 sales@igus.co.uk motion plastics® Perfect for robots igus® the-chain ... moving energy made easy ... Save time & increase reliability ... triflex® TRCF for maximum robot reliability: 3-chamber system for large hoses and cables. Easy to open using a screwdriver and easy to vary the length. Now 25% more push-pull strength. Available in sizes 65, 85,100 Ø, and in dresspack modules. More at www.igus.co.uk/triflex
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