Mechanics, connectors, relays 16.03.2020 16:34 16.03.2020 16:34

The binary outputs of the system are divided into standard electromechanical relays, solid state relays (usually referred to as SSR), simple triac outputs, and DC semiconductor outputs (sometimes called "transistor outputs").


The outputs of the system designed as electromechanical relays are the most common and versatile outputs with high resistance and versatility; however, they also have their limitations and require adherence to certain principles:

  1. The relay has a limited number of operations (expressed by the mechanical and electrical lifespan of the contact). It should be noted that the opening and closing relays in one-second intervals can destroy it within a few months! Switching more frequently than once every few minutes requires using a semiconductor output - usually the SSR.

  2. The capacitive loads (switching LED power supplies, some fluorescent lamps ballasts, etc.) and inductive loads (coils of contactors or valves, etc.) significantly reduce the maximum switching capacity of each relay, and also the maximum number of operations (electrical lifetime of the contact). For more information about the impact of capacitive and inductive loads, see Chapter Interference suppression, application of suppression measures.

  3. Common relays that do not have increased maximum switching current ("inrush current") are not suitable for switching capacitive loads. Suitable relays for capacitive loads are those with a 16A contact, which are either in the reinforced version, or with a tungsten fore-contact.

  4. All relay outputs of the basic and peripheral Foxtrot, CFox and RFox modules are made without internal fuses, so a protection of circuits switched by relay outputs must be dealt with as part of the installation. Also the interference suppression and protective circuits must be configured as part of the installation, if necessary.

  5. A disconnected relay does NOT represent a secure separation of circuits in terms of protection against injury (isolation voltage of the disconnected contact does not reach the values for secure separation of circuits).