How to Extend the Life of Your Smart Factory’s Wireless Beacons
January 23, 2020
| By: Reno Rossetti
Principal Writer, Maxim Integrated
Industry 4.0 has given us smart factories, which are highly digitalized and connected (Figure 1) for adaptive manufacturing as well as increased throughput. The increased intelligence in these manufacturing facilities is not only enhancing productivity, but it's also making it possible to identify and fix any breakdowns on the factory floor in real time with little human intervention. For the past several decades, automation has been the key driving force in increasing factory efficiency. With advances in communication, big data, artificial intelligence (AI), and the internet of things (IoT), we are moving ever closer to making factories truly smart.
Figure 1. Bluetooth Beacons in the Smart Factory
The connected factory uses an IoT framework to connect devices, assets, and sensors across the factory floor. These sensors and devices gather data not only from tools and machines, but also from materials, goods, indoor vehicles, and even personnel on the factory floor. The data gathered from these connected devices can be analyzed, using artificial intelligence (AI) to identify trends, patterns, and key insights into the daily operations and workings on the factory floor, ultimately resulting in reduced machine downtime and added flexibility for the factory.
To seamlessly enable this connectivity, wireless beacons are attached to equipment and materials, making them trackable either with simple apps based on smartphones or with more sophisticated, server-based systems. These beacons need to be small, cost-effective and long-lasting, while being powered by inexpensive disposable batteries. Wireless technologies used in these applications could include Wi-Fi, Bluetooth Low Energy (BLE), ultra-wideband (UWB) and radio-frequency identification (RFID), each with varying degrees of location accuracy, range, and battery life. Finally, the beacon's electronics must consume minimal power. BLE beacons are typically favored in many applications as they provide high positional accuracy, while still being inexpensive and low power.
Figure 2 shows a typical beacon block diagram. A single alkaline battery, supplying a charge of up to 2700mAh, powers the on-board controller, sensors, and radio through a DC-DC step-up regulator. It is not uncommon to see a single coin-cell in some systems, although this example uses an AA battery.
Figure 2. Typical Beacon Block Diagram
The various sensors collect data, which is then transmitted by the radio for 20ms to a centralized receiver. For the next 980ms, the beacon is in sleep mode. In sleep mode, the boost converter is loaded with a leakage current of 0.73µA, while a radio current pulse of 3.2mA peak is required for data transmission. The boost converter load profile is shown below in Figure 3.
Figure 3. Beacon Current Profile
In one typical indoor asset-tracking application, the system must last for two years using only a single alkaline battery. A typical boost voltage regulator has a leakage current of 0.2µA, quiescent current of 10µA, 85% peak efficiency, and 50% efficiency at low current. Assuming 1.5V input and 3.3V output voltage, with an output sleep current of 0.73µA, the average current drawn from the battery is 168µA, causing the battery to fall 61 days short of two years.
The MAX17222 nanoPower synchronous boost converter addresses the shortcomings of the previous solution. It offers high efficiency, a 400mV to 5.5V input range, a 0.5A peak inductor current limit, and an output voltage that is selectable using a single standard 1% resistor. A novel True Shutdown™ mode yields leakage currents in the nanoampere range, making this a truly nanoPower device.
The True Shutdown feature disconnects the output from the input with no forward or reverse current, resulting in very low leakage current. If a pullup resistor is used to enable/disable operation, the pullup current in True Shutdown mode must also be accounted for. If instead, the enable (EN) pin is driven by a push-pull external driver, which is powered by a different supply, then there is no pullup current and the shutdown current is only 0.5nA—much lower than the 0.2µA in the typical case discussed earlier.
With the boost converter's 92.5% efficiency at peak current, 1.15µA total input quiescent current, and 0.5nA shutdown current, the beacon can last more than two months longer than with a typical voltage regulator (see Table 1).
Table 1. Battery Life Comparison Between Two Regulators
|2700mAh, VIN = 1.5V, VOUT = 3.3V|
|IOUT_TRANSMIT mA||ηPEAK%||ηLOW CURRENT %||IIN_AVERAGEµA||Years||Delta Days|
The MAX17222 trades off the traditional resistor-divider that is used to set the output voltage value with a single output selection resistor (RSEL). The chip uses a proprietary scheme to read the RSEL value that consumes up to 200µA at startup only. A single standard 1% resistor sets one of the 33 different output voltages, separated by 100mV increments between 1.8V and 5V. The result is a small reduction in bill of materials (BOM) (one less resistor), simplified inventory (a single regulator for multiple applications), and lower quiescent current. Learn more about ways to extend the life of wireless beacons by reading the design solution, "Triple Punch Extends the Life of Your Smart Factory Indoor BLE Beacon."