Traditionally control panel design has been based on ice cube relays and timers, with PLC's only being used for highly complex systems involving hundreds or thousands of logical functions. Relays were seen as cheap, simple and very reliable, PLC's were seen as being highly technical and expensive.
Enter the smart relay. A small device not much larger than a traditional timing relay and capable of replacing a hundred electro mechanical relays and timers. Smart Relays are an excellent replacement for control logic as small as a dozen bits and any panel with 2 or 3 timing relays can be candidate to be designed with a smart relay in place of electromechanical devices.
Cost: In panels using multiple timers, external sensors, and other logical devices, smart relays can provide significant cost savings in both materials and labour. The reduction in physical wiring needed to operate the control logic saves panel building time. This is especially relevant where a more than one copy of a panel is being built. You only need to write the logic once and copy it to each new panel, many programs can be reused on new projects. Using traditional methods, the logic needs to be wired for every panel.
Reliability: By reducing the number of physical wire connection and keeping the logic digital Smart Relays reduce the number of potential failure points. The number one cause of panel problems are loose wiring connections.
In the unlikely event the Smart Relay fails, diagnostic and troubleshooting is simple. Most Smart Relays offer an ethernet port and a physical display screen. Connect to the relay remotely, or bring up the error code on its screen and check the problem. If the Smart Relay has failed, quickly download the program into a new unit and plug it in. The system is back up and running, no one had to get out a multimeter.
Future Proofing: By using a Smart Relay even simple control panels can be quickly upgraded to perform new functions by changing the code and adding on new functions. In the case of most panels relying on ice-cube relay logic there may not be enough room left in the enclosure to add much in the way of new logic and changing the existing logic requires physically rewiring the panel.
Smart Relays with ethernet allow remote monitoring and control for even the simplest control panel. The internet of things is touching more and more of our world. Having a mine dewatering pump controller be able to call for help in the event of a failure or having all the water wells in a regional district upload their run data to a central controller could save money and provide valuable data to engineers and planners.
For all the engineers and designers reading this, don't be afraid of the Smart Relay, any time you consider a panel with more than 3 relays and timers consider using a smart relay.
James is the owner and founder of Tusk Automation, a provider of control and power distribution solutions.