The Telegea Smart Hub has no on board relays mounted to reduce the hardware cost. For simple monitoring and data logging tasks,  relays are not needed and therefore would be wasted on the board.

However, relays for controlling tasks can easily be added to the Telegea Smart Hub by connecting external relay cards, via the USB ports. USB relay cards are available from different vendors which mount typically from 1 to 16 relays. Installation is very simple, only a USB cable is required between the Smart Hub and the relay card. No external power supply is necessary as the cards are powered directly from the USB port (for cards with max 4 relays). If more than 2 cards need to be use, a USB hub is required.

The software support for single and multiple relay cards was recently added to the Telegea Smart Hubs platform service layer. Thanks to the open source project crelay, a number of the most commonly used relay card types are supported. Multiple cards can be used by identifying each card with its unique serial number. The relays on the external USB cards can be controlled the same way as relays connected to the GPIO lines, for autonomous control algorithms or by controlling them manually from the Telegea Web interface. That means that existing applications don’t need to be modified and also the user interface does not change.

This is an important milestone in implementing a modular hardware architecture with the goal to provide an extremely cost efficient system for a wide variety of applications.

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