Tech Briefs

Batteries in sensors last longer – in some cases, more than ten times longer.

A voltage detector chip was developed that requires only a few trillionths of a Watt (picowatts) to activate other circuits, enabling engineers to design sensors that continuously listen, without using power from a battery or mains. The result is smaller batteries, or a battery life that is extended, in some cases by years. The voltage detector can also eliminate standby power.

The ultra-low-power UB20M voltage detector chip. (University of Bristol)

The patent-pending UB20M voltage detector, or keep-alive device, is a chip that, when combined with a suitable sensor, eliminates standby power by enabling zero-power sensing and listening. It allows circuit designers to develop circuits that perform continuous monitoring without using battery power, and to implement wireless wakeup with zero receiver power. The chip is a sensor-driven circuit that requires no power supply; instead, it uses a fraction of the power contained in the output signal of the sensor.

The ultra-low-power voltage detector provides sensing that is continuous and free because it is able to respond to minute quantities of power from unpowered sensors. No battery or other power is needed for the device to stay alive and listening, and battery maintenance is therefore reduced or not needed.

An electronic sensing device uses power to both listen and react. In sensors such as security alarms, activity monitors, and other Internet of Things devices, the energy to keep the device alive and listening can far outweigh the energy used to react. In these cases, it is especially important to eliminate listening power to increase battery life and make a system that is less environmentally wasteful.

In response to this challenge, the research team, with government support, has developed a method of eliminating the power drain used to listen by using minute, insignificant quantities of energy from the event the device is waiting for, such as movement of an asset tracker, or infrared light from a TV controller. This energy switches on mains or battery-powered devices exactly when needed. The voltage detector chip is also small enough to fit into many autonomous electronic devices.

The voltage detector chip uses more than a thousand times less energy than existing detectors to create a turn-on signal — merely five picojoules of energy, and only around half a volt. Many sensors can provide this without requiring a power supply, making listening effectively free.

There are a number of areas in which it would be beneficial to reduce the listening power to zero including mains-powered equipment where savings for consumers and the environment are made; battery-driven sensors and monitoring systems in which long-term reliability and battery life are increased, and size is decreased; and remotely powered sensors, as these can be made smaller by reducing battery capacity. It also reduces the power needed to remotely control these devices, and the sensitivity of the voltage detector chip also allows the elimination of mechanical switches. The chip also can be used to generate sensing data only when useful data is available, which saves processing power.

For more information, contact Bernard Stark at This email address is being protected from spambots. You need JavaScript enabled to view it., or visit here.

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