DMC completed the electrical design and firmware programming of a custom circuit board capable of acting as an uninterruptable power supply while also abstracting the door control hardware from the main kiosk controller.
Although uninterruptable power supplies are available as off the shelf solutions, they would have added a significant cost premium to the overall system. Because this application required the UPS to supply power only for a few minutes, DMC and the client opted to implement the UPS functionality on a custom circuit board. To save cost on the overall system, the client also requested that additional IO be included for controlling external door latches.
DMC designed the UPS system using supercapacitors to provide power to the main system. DMC chose a supercapacitor charge management chip made by Linear Technology to coordinate the charging and power path management. An additional requirement was that the PCB notify the kiosk of power loss and force a shutdown if power was not restored. Because of this requirement, DMC opted to include an STM32 microcontroller onboard in order to allow for flexible logic and the possibility for future additions to the system.
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