Wireless controlled smart power supply

The needs

One of SEMAR customers, which provides IT solutions and services for indoor environment monitoring, was looking for an optimized solution to power feed both their air monitoring and purification systems.

Furthermore, the required device had to provide a wireless communication (WiFi and BT/BLE) to connect with a remote platform to schedule the working cycles of the air purifier. This calendar-based scheduling had to be dynamically configured (locally or via a remote management) and autonomously implemented even in absence of wireless connection.

For some installation scenarios where a WiFi network is not available,

the device had to be able to connect wirelessly (WiFi and/or BT/BLE) to the air monitoring device already present, in order to use its integrated cellular connectivity as a gateway for the remote platform.

Additional features desired by the customer, to further expand the possible use cases of the device, were the optional presence of multiple isolated I/O dry contacts and a RS485 ModbusRTU interface.

The absence on the market of a single device containing all these features led the customer to ask us the development of a dedicated product for this specific application.

The challenges

  • 48Vdc 60W main power output for the air purifier
  • Calendar-based scheduling of the 48Vdc main power output
  • 5Vdc 1A auxiliary power output on USB type A port for the air monitoring device
  • WiFi and BT/BLE wireless communication interfaces for local and remote control
  • Multifunction button for manual control
  • Customizable APIs for local and remote control with secure transport protocols
  • Optional RS485 ModbusRTU interface
  • Optional I/O isolated dry contacts

The realization

The PSW device is a smart power supply with DC main power output (12, 24 and 48Vdc, 60W max) that can be activated/deactivated manually or according to an automatic program, controlled and configured using a wireless connection. This power output can optionally support programmable dimming and/or fading behaviours (through configurable PWM control) or the activation of single/periodic patterns, useful in specific lighting applications.

The device also has an auxiliary power output (5Vdc 1A) on a standard USB type A connector.

The PSW is expressly designed to be used in those scenarios where a generic electric device, requiring a DC supply of up to 60W, should be activated remotely or on a calendar-based program.

The 5Vdc auxiliary output also simplifies the installation of other sensor devices which require a standard USB power supply. The use of a single connection to the power grid therefore speeds up system installation and improves the operational reliability.

In addition, the PSW can optionally be factory equipped with a RS485 ModbusRTU interface, two input and two output dry contacts. This allows the connection and the control of further external devices, expanding the installation with more complex systems.

The control and configuration of the PSW takes place using dedicated APIs via the 802.11bgn WiFi interface in 2.4GHz band (both local and remote in AP and STA modes available simultaneously) or, only locally, via a custom service on the BLE 4.2 service. These APIs are available in a secure and simultaneous way through a large number of services and protocols (http(s), mqtt(s) and ws(s) client, http server, ws and ble/gatt), which also include a configurable management of digital certificates for SSL mutual authentication.

The PSW is made of plastic (158x90x60mm) with a button and a green LED to ensure a faster local control of its features.

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