Relay/Open-Collector Outputs Configuration (MEXM)

Relay/Open-collector output connections

The MEXM-1 module can control physical relays, or use them to route open collector contacts to the NC terminal, as shown in image below.

The MEXM’s physical relays provide high isolation and accept higher voltages and currents than the open collectors. Open collectors can be used to control equipment that have digital external control ports.

Relay / Open collector output

Relay output

The MEXM-1 physical relays can support 0.4 A @ 70 VAC, and 2 A @ 30 VDC.

Relays can be wired normally-open (NO) or normally-closed (NC).

Open-collector output

Open collector outputs can support a DC current of 100 mA at 12 V.

Warning: Exceeding the MEXM-1 power supply voltage on the open collector can damage the transistor. For higher voltages, choose relay outputs instead of open collector outputs.

Relay DIP switches

At the factory, Relay DIP switches are set to Relay control. To gain access to the relay DIP switches, loosen the two screws retaining the clear plastic cover to the right of the MEXM-1 module (see image below) and remove the cover.

Relay or open-collector controls are independently set for each of the 24 MEXM-1’s outputs. The number between the two DIP switch rows indicates to which output the settings are applied.

Relay/Open-collector output mode DIP switch Set to
Open-collector OC

Relay/Open-collector DIP switch settings

Relays DIP switch access and screw location

In the Open-collector control settings, open-collector contacts are through the relay NC and COM terminals.

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