How we develop low-power IoT devices: A look at our 7-inch e-paper frame
In a world where sustainability and long battery life are becoming increasingly important, the design of energy-efficient IoT devices is crucial. At paperlesspaper, we are dedicated to developing devices like our 7-inch E-Paper frame, which operate with minimal energy consumption, enabling autonomous and low-maintenance information display. But how do we achieve this?
PCB und Nordic Power Profiler Kit IIThe right selection of components: Crucial for low energy consumption
The first and most important step in designing a low-power device is the careful selection of each component. We focus on two key metrics:
Quiescent Current: This is the current that a device or component consumes when it is idle or in a sleep mode and not performing an active task. A low quiescent current is crucial for long battery life, as most IoT devices spend the majority of their lifespan in standby mode. For example, our step-down converter for power supply (Step-Down) TPS62840 has a quiescent current of typically only 60 nA.
Efficiency: Efficiency indicates how much of the supplied electrical energy is actually converted into usable output power and how much is lost as heat. High efficiency is particularly important when the device performs active tasks (e.g., updating an image) to minimize power consumption during these phases.
The main controller: The heart of energy efficiency
The main controller is the central control unit of the device and therefore a major factor in the overall power consumption. We use the ESP32-C6-MINI.
PCB mit ESP-32 C6 MCUExtremely low power consumption in standby: The MCU has various power-saving modes. In deep sleep mode, this controller can reduce its power consumption to just 7 µA. This capability is essential to ensure battery life over months or even years, as the controller sleeps most of the time and only wakes up briefly for tasks.
Low consumption during operation: Even when the controller is active, we ensure low power consumption. This is achieved through optimized software and efficient hardware architectures. It is particularly important that the controller spends as little time as possible in this state.
Connectivity: The choice of technologies significantly influences power consumption. Our 7-inch E-Paper frame uses Wi-Fi for setup and updates. Additionally, Bluetooth Low Energy is used in the setup process. Modern WiFi standards already offer good energy optimization possibilities. Our hardware is ready for this, but it will take a few more years until end devices like routers in home networks master these technologies.
E-Paper display and electronics in standby
E-Paper displays are inherently energy-saving, as they only consume power when changing the image and can maintain the displayed image indefinitely without further power supply. It really works! Try removing the batteries from your picture frame. Compared to conventional displays, the image will not change!
In our 7-inch E-Paper frame, the standby consumption of the E-Paper display is only 30 µA. The entire remaining electronics, including power management (e.g., BQ25172 charger and TPS62840 step-down converter) and sensors (e.g., KXTJ3-1057 accelerometer with 0.9 µA in disabled state), contribute to an impressively low total standby consumption of the electronics + display of 70 µA.
Through this consistent focus on low-power design, our devices like the 7-inch E-Paper frame can achieve a high battery life of up to 12 months, making them a sustainable and flexible solution.
In our gallery, you will find some pictures of how we develop, test, and verify low power devices.
You can pre-order the PaperlessPaper paper 7 now HERE!
