DC1 series controllers are equipped with mechanical relay outputs that can be used as a programmable switch to connect two wires. The logic controlling the relay can be freely programmed, so the relay can be activated with button press or for example when roller speed is greater than 20km/h.
The relay built in DC1 is rated to 250VAC and 16A resistive load.
Switching of highly inductive loads such as dyno fan motors or fume extractors is not allowed directly with the built-in relay and will lead to its damage after few switching cycles.
Big external loads should be switched with use of external contactor adequately rated for such load.
External contactors for heavy loads often are equipped with quite big coil that will create high voltage arcing on the DC1 internal relay contact. This arcing, if big enough, can disrupt DC1 operation. To eliminate the arcing, the following rectifier and flyback circuit can be used to drive the contractor.
In typical case, the whole circuit can be made from standard 1N4007 (1A, 1000V) rectifier diodes. Inductive kickback and arcing from the contractor coil can be eliminated with a parallel flyback diode. To be able to use the flyback diode, the voltage must be rectified with the rectifier diode.
After creating the circuit, make sure that your contactor operates correctly with the rectified current. Check if it latches completely and that it doesn’t overheat.
Ready-made 1N4007 diode DIN rail modules are available for convenient creation of required circuit.
A good solution to the issue of voltage spikes created by the contactor coil is to use a contactor with build in circuit that suppresses the spikes. An example of a contactor with this function is ABB ESB series contactor.