It’s been over two years since I started tinkering with the idea of a solar-powered, ePaper digital photo frame. My first version was functional but had a number of issues that made me go back to the drawing board.

As a reminder, my goals were to build a digital photo frame that:

• Requires no electric outlet connection.
• Requires no form of maintenance. You put it up and it works “forever” (it becomes a heirloom device).
• Uses either open hardware and open standards or hardware and standards that are so common that it should be trivial to perform changes or updates “many years in the future”.

The biggest issue with version one was the battery. After a few hundred load/unload cycles, it went bust — as I expected. There are many projects and even commercial products out there using a larger li-ion battery than the one I used for my v1, some of which promise up to two refreshes a day, for an entire year, before needing to recharge the battery.

Many people would think that it’s perfectly acceptable for an object that for 99.9% of its life will just hang there and be beautiful. Many people are not me. I want my device to “be alive”. Refresh as much or as little as it can, following the cycles of nature (in essence: use as much light as the panels receive to power the device). And of course, there still isn’t a device quite like it out there, so bonus points for working on something novel.

Another issue with v1 was its wastefulness. A whole Raspberry Pi had to be powered and booted to perform the image swap. There really is no need for all that hardware to change a picture.

V2 fixes those two main issues. It does away with the battery, replaced with a big, fat capacitor. And the Raspberry Pi is now slimmed down to an ESP32 microcontroller. In a nutshell, the solar panels slowly charge the capacitor. When a certain voltage is reached, the circuit is opened, powering the ESP32 which boots a simple program that either down