Making sensors smarter

Louise Davis

Bianca Aichinger reveals how to efficiently power sensors in the Internet of Things

Without sensors, there would be no Internet of Things (IoT). They measure and record temperature, brightness, movement and many other parameters and transfer the data to the smart control devices.

Sensors, however, need power. Although their power consumption is generally very low, they cannot work without it. Here we describe how the service life of batteries can be considerably extended.

With the arrival of Industry 4.0, cyber-physical systems, the IoT and cloud computing have found their way into modern factories.

Operating as integrated communication networks, cyber-physical systems take decisions and act, while communicating in real-time with other systems as well as with humans. This development has made it possible to integrate more and more devices into networks where they combine, process and exchange ever-larger volumes of data. However, every single sensor in such a network must be supplied with power – be it through a central power supply, battery or energy harvesting devices.

Many IoT and Industry 4.0 applications run with 3V coin batteries, which are not only cheap but also very reliable.

However, such batteries need to be changed quite frequently. A fully charged CR2032 coin battery supplies approximately 3.2V. After only a few operating hours, the voltage drops however to below 3V, which might not be sufficient for certain wireless modules (WLAN, Bluetooth, LoRaWAN, etc.).

As a result, transmission can become unreliable or the signalling range might suddenly be limited.

Using switching regulators

The R-78S boost-switching regulator from Recom has been specially developed for battery-powered IoT devices.

The plug & play module provides a stable output of 3.3V from input voltages of as little as 0.65VDC to 3.15VDC, squeezing the last bit of energy from the battery cell.

The R-78S thus enables users to run microprocessors, WLAN/Bluetooth modules and IoT systems with a single 1.5V battery or cell, which has a much longer service life than a conventional coin battery.

The figure shows a typical application of the R-78S in a wireless module.

The circuit is only activated for brief periods to send data. During these short times, the entire circuit consumes around 600µW. When not sending data, the circuit is in sleep mode.

During these times, the R-78S is powered by a buffer capacitor and consumes only 7µA. If the capacitor charge drops below a certain limit, the circuit is briefly activated for recharging. This technology guarantees reliable, maintenance-free operation for periods of 10 years and more.

As converters are affordable, the extra investment pays for itself in no time thanks to much lower battery and maintenance costs.

Turning away from wires and batteries, sensors in condition-based maintenance applications could be supplied by micro generators (MEMS), which harvest energy of up to 4mA through environmental conditions, such as vibrations, heat, light or temperature differences.

An R-78S from Recom is ideal to support the MEMS in providing a stable output voltage to the sensor application.

As the IoT is really an internet of sensors, it depends on innovative power supply solutions.

Recom offers intelligent components that help save battery power with the R-78S boost-switching regulator. These regulators squeeze the last bit of energy out of the battery, so that applications can be run for more than a decade without problems and no need for servicing.

Bianca Aichinger is with Recom Power

Recent Issues