We designed True Wireless Valve (TWV) to achieve exceptional energy efficiency, enabling it to operate for up to two years on a single set of batteries. A key factor in this efficiency is the device’s ability to enter sleep mode. TWV cannot remain asleep for too long, however, as it must be ready to respond instantly to commands from the user or automation signals from the hub.

By default, a Zigbee hub stores messages for end devices for a maximum of 7.68 seconds. If a message is not delivered within this time frame, it is erased. Therefore, TWV must check for messages from the hub at least every 7 seconds to ensure none are missed. To account for any variability, we use a 5-second interval.

Five-second polling intervals in real-world use

In practice, TWV wakes up every 100 milliseconds to check for any internal tasks that need to be completed. If no tasks are pending, it returns to sleep. Every five seconds, the device activates its radio, which consumes a lot of power, to send a query to the hub and check for any commands to open or close the valve, whether triggered by the user or through automation, such as a signal from a leak sensor. This approach ensures that TWV never misses a command from the hub and is always ready for safeguarding against potential flooding.

When TWV detects radio-channel activity, it reduces the polling interval to 0.5 seconds to respond to messages as quickly as possible. After completing data exchanges with the hub, the polling interval returns to five seconds to maximize energy efficiency.

Through the integration of variable polling intervals, TWV strikes a balance between energy efficiency and responsiveness. By effectively managing its sleep and wake cycles, it ensures prolonged battery life without compromising its ability to respond swiftly to network commands.

We hope this update has provided a clear understanding of TWV’s power-management strategies and how they contribute to its long battery life. In our next post, we’ll dive into the specifics of the device’s IP-rated design and how we’re achieving it. We’ve passed the midpoint of our crowdfunding campaign and welcome your support if you find TWV interesting. Stay tuned for more updates!