ATmega2560 powers UPS solar controller

Markus Loeffler has debuted an Atmel-based solar UPS controller.

Powered by the popular ATmega2560 microcontroller (MCU), the UPS controller comprises three primary blocks:

  • 120V AC unit
  • 12/24V DC unit
  • Microcontroller and sensors

“The controller [is tasked with] transfer switching between the solar powered inverter and main utility power to optimize battery life and maximize solar energy usage,” Loeffler explained in a recent blog post.

“It is also monitoring phase shift between utility power and inverter and only switches in phase-sync to protect your equipment. [In addition], the controller offers a standby UPS mode to provide surge protection and battery backup around the clock.”

According to Loeffler, the run-time for the battery-operated UPS mode depends on the type and size of batteries and rate of discharge, as well as the efficiency of the inverter.

“A wide variety of inverters and battery sizes can be combined. You can setup a minimal system with 12V, 10AH and go up to 24V, 500AH using common lead-acid batteries. [Plus], the controller has a simple menu driven setup mode where levels for different kinds of battery types can be adjusted,” he noted.

“If you are a hacker, Maker, inventor or DIY person, and like to build your own prototypes this is a new platform you can use to build electronics that plug into 120V and control high power items like heaters, pumps, lights, etc.”

Aside from Atmel’s ATmega2560 MCU, key UPS solar controller feature and specs include:

  • AC 2x inlet, 1x outlet 10A @ 120VAC, 60Hz
  • Solar panel terminal 50A @ 12-50V
  • Charge controller terminal 50A @ 12/24V
  • Inverter terminal 50A @ 12/24V
  • Battery capacity range 10-500AH @ 12/24V
  • Temperature range -20 … 60C
  • RGB display
  • Two menu buttons and a slide switch for the operation mode
  • 1.5A @ 5V USB connector (to charge phone, pad, etc directly)

“The controller is essentially an Automatic Transfer Switch (ATS) that switches a load between two sources. It automatically switches when it senses one of the sources has lost power. The type is called open transition transfer switch. It is a break before make transfer switch which breaks contact with one source of power before it makes contact with another,” Loeffler added.

“This prevents back-feeding from an inverter/generator back into the utility line. The ATS will automatically tell the inverter to start. Once the ATS sees that the inverter is ready to provide electric power, the ATS breaks the home’s connection to the utility grid and connects the inverter. The inverter supplies power to the electric load, but is not connected to the electric utility lines.”

Interested in learning more? You can check out the project’s official page here.

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