When building a project to operate on battery power for long periods of time, having a microcontroller with a reliable and extremely low-power sleep mode is critical. When processing power isn’t needed, it should be able to wait around using almost no energy until an interrupt triggers it. Once triggered, the CPU performs its tasks and then puts itself right back to sleep, making sure the battery lasts as long as possible. Unfortunately, not every microcontroller has sleep capabilities or has an acceptably low level of power use for maximizing battery life. For these systems, a tool like this power manager might come in handy.

The small PCB, called the powerTimer, essentially acts as a middleman for power delivery to another microcontroller. On the PCB is an RV3028-C7 real-time clock, which uses a mere 45 nA of current and can interact with the second microcontroller through a timer or alarm. When commanded, the powerTimer uses an SR latch as its main control circuit, allowing single button presses to change the power state for the second microcontroller. Once the powerTimer powers up the second microcontroller, that microcontroller can communicate back to the powerTimer with a “DONE” signal, and once this signal is received, the powerTimer will cut power and wait for the next interrupt to occur.

The project’s creator, [Juan], had this idea for an ESP32 with a camera module.  While it does have a sleep mode, the ESP32 wasn’t nearly low-power enough to get the battery life that he wanted. With a modular system like this, it can be used in many other applications as well. PowerTimer is one of the entries in our 2026 Green Powered Challenge.