Gartner states that more than half of major new business processes and systems will incorporate some element of the Internet of Things (IoT) by 2020. Although some applications, such as connected home, will invariably use mainline power, others will require a battery that can be recharged. For these devices, engineers must focus on creating an energy budget that accounts for the power consumption of the radio powering the connection.
Reducing power consumption of these radios when creating a connected product will not only help lengthen the time between charges, but also extend the device lifespan. (Reducing power consumption is also better for our environment.) Below are a few strategies to deploy when developing an IoT product while leveraging three different types of connections.
Selecting a radio
When it comes to the development of connected products, most creators will choose to build a radio based on the needs of the application. BLE radios work well for small, low-powered devices, but need a gateway to communicate with the internet. Wi-Fi devices require a Wi-Fi network and router to communicate. Cellular devices are freed from the constraints of Wi-Fi, enabling much more remote applications, but as you move from Bluetooth to cellular, the power required to send and receive messages increases accordingly.
Wi-Fi power consumption correlates directly to the amount of data the radio is transmitting. High bandwidth applications, such as downloading web pages or streaming music, will consume much more power than low bandwidth applications like transmitting sensor data. For high bandwidth applications, it is ideal to connect directly to an AC power supply or have a charge management circuit that allows for frequent recharging of the device to ensure the device stays powered-on.
That said, the best way to conserve power for an IoT device with a wireless radio is to ensure that the radio is only fully powered when actively in use. However, if the radio must be on in a Wi-Fi device, it is possible to keep it in a more efficient “power saving mode” which sets the internal oscillator to a lower frequency to conserve power. This mode is only used when the radio is not actively transmitting, but can result in significant power savings and decreased impact to the device’s energy budget.
Cellular (2G/3G/LTE) mirrors Wi-Fi’s power consumption in that it correlates directly to data usage. To reduce cellular power consumption, it is important to choose an efficient and secure communication protocol that requires minimum overhead.
Leveraging dedicated API endpoints in the cloud can also reduce data usage and thus conserve power. Instead of programming an IoT device to send and receive messages directly to and from open Internet services, it is preferable to send smaller amounts of data using a byte-efficient communication protocol designed for IoT to the cloud, where the data can be stored, processed and retransmitted if necessary. An example of the bandwidth efficiencies enabled by a dedicated cloud service is a remote weather station that transmits data to multiple endpoints like weather.com, Google Cloud Platform and NASA.
Bluetooth Low Energy
Bluetooth Low Energy (BLE) is one of the most promising low power consumption wireless technologies for IoT applications. Everything from physical design to use models is designed to keep power consumption at a minimum.
But to further reduce power consumption, a BLE device can be kept in sleep mode most of the time, but when an event occurs, the device will wake up and a short message will be transferred to a gateway, PC or smartphone. Ultimately, the active power consumption is reduced to a tenth of the energy consumption of classic Bluetooth. In low duty cycle applications, a button cell battery could provide up to a year of power.
Regardless of the type of connection behind an IoT product, minimizing power use can be a challenge. However, it is also critical to keeping energy and component costs under control. Radios are a key component of the energy budget for IoT products and the strategies outlined above, combined with smart design and component selection, will help developers navigate the early days of product development to ultimately create cost-effective IoT products that last longer between charges.