Soft Power Switch Circuit for Battery-Powered Devices

Alternative to Toggle Switch Uses an ATtiny10 MCU

- Michael Hansen

The battery in a battery-powered CPU system typically is activated with a toggle switch. In this article, Michael explains how he overcame the limitations of toggle switches by creating a solution that allows a device to be turned on and off using a simple, momentary push button. Additionally, the CPU system, itself, can control the power, making the solution compact, efficient, and inexpensive to construct.

I frequently design devices such as laser tag guns and lightsabers, which typically include a CPU board with a USB socket, a lithium-ion battery, and a built-in charger. This setup allows the CPU system to be updated via the USB interface, but also serves as the charging connection for the battery. However, using a toggle switch to control the battery introduces some limitations:

• The CPU system cannot turn off the power when the battery is running low.

• The CPU system cannot automatically turn on the battery during charging.

• The toggle switch occupies space and cannot be repurposed by the system CPU.

For years, I searched for a solution to address these issues. While some commercial products include this functionality, I was unable to find a readily available, comprehensive solution. Partial solutions exist for individual problems, but none resolved all the challenges.

In this article, I describe the custom solution I developed. It effectively addresses the issues mentioned above, while remaining small, efficient, and inexpensive to implement.

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