As IoT deployment ramps up with 5G connectivity, devices will need to be even more energy-smart despite 24/7 operation.
When designing portable IoT devices, battery life is a key concern.
Device designers need to identify the critical events that contribute to power consumption and how frequently those events happen. They also need to make design changes or trade-offs to optimize battery life.
While there are many ways to conserve energy—for example, balancing active functions and deep sleep mode—there is a baseline of power consumed by a certain part of the circuitry that needs to be on at all times. One example would be a pacemaker. A certain part of the circuitry will need to be always on for continuous monitoring, therefore limiting the battery life.
Fortunately, many techniques are available to make electronic circuitry more power-efficient, helping to extend the battery life of the device. Here are a few examples.
- Energy harvesting is an example of how one can prolong battery life or maybe even eliminate a battery completely! It is a method of collecting energy from the environment to power electronic circuitry.
For example, RF energy harvesting captures ambient electromagnetic energy (from Wi-Fi signals, microwave ovens, and radio broadcasting) and converts it into a usable continuous voltage (DC) with an antenna and a rectifier circuit.
Other energy harvesting methods include thermoelectric conversion, solar energy conversion, wind energy conversion, and vibrational excitation.
Today, several companies are creating energy-harvesting chips that eliminate the need for battery replacements for low-power IoT devices- here is an example.
- Wireless connectivity standards (cellular and noncellular), have developed features and optimization techniques that help maximize IoT device battery life. Wireless standards such as LTE-M and 802.11 wireless LANs have features such as power save mode (PSM) and extended discontinuous reception (eDRX) to lower power consumption.
PSM allows the IoT device to be in a sleep or ‘dozing’ state at a fixed time, waking up only to transmit and monitor data before going back to sleep, all the while remaining registered with the network. The device and the network negotiate and optimize the timing based on the application’s requirements. Since the IoT device is inactive during PSM mode, power consumption is lower, helping prolong the battery life.
eDRX can be incorporated into IoT devices as an extended LTE feature, working independently of PSM to obtain additional power savings. eDRX greatly extends the time interval during which an IoT device is not listening to the network. While not providing the same level of power reduction as PSM, eDRX may be a good compromise between device reachability and power consumption.
- Power-efficient circuitry. Sometimes, a certain hardware design, software, or firmware changes can cause the circuitry to draw more power. Different climatic conditions can also cause power consumption to vary. Device designers often analyze how an IoT device consumes power in different scenarios by capturing and breaking power consumption down to hardware subsystems.
Take for example, an air quality monitoring sensor that uses low-power wide-area network (LPWAN) technology. Device designers need to optimize the sensor’s design to ensure that the coin cell battery could last for at least 10 years. They need to spend a lot of time testing many different real-life scenarios and correlating the events to the current consumption of the product, down to subsystem level — which is incredibly frustrating.
On top of that, these steps must be repeated to analyze and verify the effects of each design change. This process is known as event-based power consumption analysis. Designers need to correlate the charge consumption profile to the RF or DC event of a subsystem. As described, the process to optimize device design can be difficult and time-consuming.
Most people can relate to the anxiety caused by a mobile phone battery that is running low. Deploying IoT devices is no different. Battery runtime is one of the most essential criteria for these users of networks.
Fortunately, available technology and solutions can help manufacturers and device designers to manage power efficiently and optimize their IoT devices’ battery life.