Powering IoT devices with small rechargeable batteries


 

There are four times as many devices connected to the Internet as there are people in the world, and the number of devices is increasing rapidly. The Internet of Things (IoT) enables businesses, communities and individuals to gather data through connected devices.

 Wearable devices such as activity monitors and smart watches are the most common IoT devices today. Wearables monitor your activity and fitness by measuring activity levels and helping you adjust your behavior to become fitter.  In a similar manner, other IoT devices can gather data about vehicles, homes, businesses, and other assets to improve their use.  A connected thermostat can increase the efficiency of heating and cooling.  A connected lock can increase the security of a home or business. Connected sensors on infrastructure can help cities anticipate failures and respond quickly when issues happen. Asset tracking can assist in the tracking and recovery of shipments.

IoT devices need power at all times. Many are powered from primary batteries, although rechargeable batteries are becoming more common. Even if the device is primarily powered by an A/C connection, often a battery backup is needed to ensure that data can be captured or stored during a power outage. Additionally, some devices are moved around such as temperature and humidity sensors, motion detectors, and asset trackers. For these devices, you can also implement a simple wireless recharging solution.

Most IoT devices include a sensor array, a microcontroller (MCU), Bluetooth® or Wi-Fi radio, and power management. Some devices also have a display or push-button inputs. Figure 1 shows a typical block diagram.

Figure 1: Block Diagram for Sensor node with Display

The bq25120 is a highly integrated battery charge management solution that integrates the most common power-management functions for wearable devices, and is also appropriate for many IoT devices as well. The bq25120 includes a linear charger, buck output, load switch or low-dropout regulator (LDO), manual reset with timer, and battery-voltage monitor. An I2C interface allows configuration of key parameters including charge current, termination threshold, battery-regulation voltage, DC/DC buck output voltage, load switch or LDO voltage, push-button timers and reset parameters, input current limit, battery undervoltage threshold, safety timer limit, battery monitor reads, and fault conditions.

The reference design for a wearable device with wireless charging reference design implements the block diagram shown in Figure 1 and is scalable to include only the features needed for a specific IoT device. With this reference design as a starting point, powering an IoT device becomes very simple.

What IoT devices are you looking forward to not charging as often?

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