A relay-based control system uses a number of electrical relays to transmit signals from control devices to operating equipment. Inputs to the control system can include level switches, temperature switches, emergency stop buttons, etc. Outputs can include electrical motors and lights. As an example, if a level switch in a tank was activated, it would in turn activate a relay in the control panel that would signal the motor starter for the discharge pump to start. Because a relay is used to transmit the discrete signal from the level switch to the pump, the wiring for this circuit can be relatively lightweight and the operation is much safer. If the switch directly controlled the pump, the switch and all the wiring would need to be sized to meet the power requirements of the pump.
In a relay-based control system, each input and output signal has an individual relay. This allows the operator to observe the operation of each independent part of the system, simplifying troubleshooting and making the operation of the control system logic much easier to understand.
Relay-based control systems are often used for simple control systems. Due to the number of relays involved in larger systems, PLC-based control systems are more common. There are fewer telemetry options available for relay based systems as well.
When designing a relay-based control system it is important to consider the number of input and output signals, the type of power available, and the required level of remote communication.
MLE Equipment designs and builds relay-based control systems using dependable OMRON relays. These systems are built in a UL-approved facility and can be built with UL, CSA, MET, or ESA approval. Please see the provided specification sheets and manuals for more detailed information on relay-based control systems.
