Sip and Sleep – It’s Good for Battery Life

As medical devices trend toward the small, portable, and battery powered, it’s not surprising that users aren’t happy when they attempt to take a critical injection or run a health status test , only to find that the battery is dead. Like a smart phone, a portable medical device must be designed to prolong battery life to the fullest extent.

Ideally it’s best to disconnect the battery to prevent the device from consuming any power when not in use. But we can’t rely on users to power the device on and off through a mechanical action like the flip of a switch; it’s too easy to forget. Instead, as thoughtful engineers, we design our devices to sleep and sip. And after sensing the device has not been used for a period of time, the accelerometer will generate a signal to put the microcontroller back to sleep.

Sleep is the device’s lowest energy state. Naturally, to extend time between charges, the device should be designed to sleep as long as possible. Most microcontrollers (the device’s control center) have built-in lower power modes that can support sleep mode. Accelerometers are often used as the trigger to pull a device out of the sleep state. When the accelerometer senses device movement (ex: medication injector being picked up by the user), it sends a signal to the microcontroller to wake up.

After waking up, the device should sip power to minimize power consumption. While selecting components optimized for low power consumption is a good start to achieving this goal, the microcontroller can again be used to help conserve power. It can intelligently disable/enable sub-circuits and peripherals (motor drivers, sensors, displays, etc.) or throttle clock frequencies and voltage supplies to reduce power draw even while the device is actively used. Sleep mode power draw can be as low as one to two percent of active mode, or as much as a third, depending on the architecture.

Sleeping often and sipping power both help to extend battery life and increase the likelihood that the device will be ready when needed. Designing for reliable power is one of the key behind-the-scenes efforts aimed at improving patient medication adherence. To find out how to help your product sleep and sip, feel free to reach out.

Abbie Shoemaker

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