Battery Power - Summer 2015 - (Page 10)

Feature Five Building Blocks of Self-Powered Wireless Sensor Nodes Niranjan Pathare, Battery Management Solutions Marketing, Will Cooper, MSP Microcontroller Product Marketing Texas Instruments Today, autonomous sensors are in use for a variety of applications. Typically found in smart buildings and factories, these sensing applications include humidity, temperature, and chemical gas monitoring. They are often placed in remote locations where line power is unavailable, so rely heavily on battery power to function. In order to provide dependable operation, batteries have to be changed often, adding to the total cost of ownership. Ownership cost includes expensive labor needed to change the batteries during routine maintenance. With the advent of the Internet of Things (IoT) just around the corner, a way to power such small sensors indefinitely is essential. By harvesting ambient energy these autonomous sensors can be powered perpetually without the need to change batteries. A typical block diagram for a remote sensing application (Figure 1) includes: 1. Energy Source: typically a battery 2. Power Management Devices: monitors and regulates energy from the energy source 3. Sensor: interfaces to the real world and takes measurements 4. Microcontroller: the brain that accepts analog or digital data, processes it, stores the results, and outputs the data to make intelligent decisions 5. Wireless Transceiver: transmits data for further processing by a central unit In this article, we look at how to replace the limited-life battery with a perpetual power source. In real life, the goal is not to eliminate the battery, but to replace it with a rechargeable storage element. An alternative is to supplement the existing battery to extend the run time of the sensing system. Energy harvesting can help to accomplish this goal. Then we review the require- ments of the microcontroller, sensor and transceiver to help you to understand how your design impacts the system's overall power consumption. A typical block diagram for an energy-harvesting, remotesensing application is shown in Figure 2. The battery in Figure 1 is replaced (or possibly augmented) by an ambient energyharvesting element, an energy-harvesting power management IC and a storage element. Figure 2. Block Diagram of an Energy Harvesting Sensor System Ambient Energy as a Power Source For sensors placed in a remote location, it is imperative that the sensor be able to extract energy from its ambient environment so it can power itself without relying on batteries. Examples of commonly available ambient energy sources are light, heat and vibration (motion). In practice, this means tapping into power sensors placed in the immediate vicinity of a well-lit factory floor, a pipe carrying hot liquid or a vibrating motor. The three most common types of harvesters are: photovoltaic (PV) or solar cells, thermos-electric generators and piezo-electric harvesters. Light Figure 1. Battery-Powered Remote Sensing Application 10 Battery Power * Summer 2015 Solar cells convert light energy to a small electrical voltage. The voltage generated per cell is dependent on the brightness of incident light (measured in Lux). This voltage is usually small, ranging from a few to hundreds of millivolts. Several cells can be stacked in series to provide a larger voltage output. Each cell has a maximum current it can provide. In series-connected cells, the maximum current is the same as the maximum current of an individual cell. To achieve a larger current, these cells have to be connected in parallel. The configuration depends on many factors including light levels expected, cell specifications and sensor form factor. www.BatteryPowerOnline.com http://www.BatteryPowerOnline.com

Table of Contents for the Digital Edition of Battery Power - Summer 2015

Battery Power - Summer 2015
Table of Contents
Wearable Medical Devices Embrace Lithium Polymer Cells
Five Building Blocks of Self-Powered Wireless Sensor Nodes
Conference Preview: Battery Power 2015
Protecting Batteries that Protect Your Power System
Batteries
ICs & Semiconductors
Components
Chargers
Industry News
Conference Review: Battery Japan 2015
Calendar of Events
Marketplace

Battery Power - Summer 2015