Barometric Pressure Sensor Serves Consumer Drone Needs

Bosch Sensortec has introduced a new high performance barometric pressure MEMS sensor: the BMP388 is ideally suited for altitude tracking in Consumer Electronics (CE) drones, wearables, smart homes and other applications. The BMP388 delivers outstanding altitude stabilization in drones, where accurate measurement of barometric pressure provides the essential altitude data for improving flight stability and landing accuracy. The new barometric pressure sensor is part of Bosch Sensortec’s comprehensive sensor solution for drones, which includes the BMI088 Inertial Measurement Unit (IMU) for accurate steering and the BMM150 geomagnetic sensor for the provision of heading data.

The BMI088 is a 6-axis IMU, consisting of a triaxial 16-bit acceleration sensor with excellent performance and a triaxial automotive-proven 16-bit gyroscope. Drones can take full advantage of the IMU’s superior vibration suppression and robustness and unmatched stability in dynamic conditions such as sudden temperature fluctuations. The BMM150 is a low power and low noise triaxial digital geomagnetic sensor designed for compass applications. Due to its stable performance over a wide temperature range, this geomagnetic sensor is especially suited for determining accurate heading for drones.

In addition to drones, the BMP388 provides a very flexible, one-size-fits-all solution for increasing the accuracy of navigation and fitness applications in wearables and smart homes, for example by utilizing altitude data to improve GPS precision or to determine floor levels inside buildings. It can also improve the precision of calorie counting in wearables and mobile devices, for example by identifying if a person is walking uphill or downhill when using a step counter.

With an excellent temperature coefficient offset (TCO) of 0.75 Pa/K between -20°C to 65°C, the BMP388 further improves the accuracy of altitude measurement over a wide temperature range. The new sensor provides an attractive price-performance ratio coupled with low power consumption and a high level of design flexibility – combined in a compact LGA package measuring only 2.0 x 2.0 x 0.75 mm³.

FIFO and interrupt functionality provide simple access to data and storage. This enables power consumption to be reduced to only 2.7 µA at 1 Hz during full operation, while simultaneously making the sensor easier to use. Tests in real-life environments have proven a relative accuracy of +/-0.08 hPa (+/-0.66 m) over a temperature range from 25°C to 40°C. The absolute accuracy between 900 and 1100 hPa is +/- 0.40 hPa over a temperature range from 25°C to 40°C.

Bosch Sensortec | www.bosch-sensortec.com

Forecasts Predict Deluge of Powerful IoT Sensors

Tech the Future: The Future of IoT Sensors
By Zach Wendt, Engineer, Arrow  Electronics

Nearly all predictions estimating how many IoT devices we’ll have in the near future number in the tens of billions. This includes devices monitoring everything from weather conditions to whether or not you need a new bottle of laundry detergent. Underneath all of these gadgets is an array of sensors that relay input back to the cloud, enabling humans—or other IoT devices—to make decisions based on real-world input. Here are a few of the sensors that, while you may not see them, will be working behind the scenes to make our increasingly connected world run smoothly:

Passive Infrared (PIR): This type of sensor will be familiar to many as part of automatic lighting and alarm systems that detect movement. They’re normally made as small components with two sensing elements inside. When they sense a change in radiation in the surrounding area, this information is passed to a security system or other device. While the sensing element is something of a commodity, what sets different devices apart are the lenses used to focus the surrounding area into different segments, allowing for a wide range of monitoring capabilities.

Inertial Measurement Unit (IMU): If you want to track how something is moving, IMUs fill this role quite well. In the case of the popular MPU-6050, it packages both a gyroscope and accelerometer in one unit, allowing devices to respond to movement. Some devices integrate magnetometer (compass) into the unit as well, providing absolute orientation with respect to the earth’s surface.

Temperature Sensor: Temperature is inextricably linked for human comfort and even storage of some foods and other goods. So, measuring this is an important IoT function. This can work via a thermocouple method where a voltage is generated by two dissimilar metals or via a thermistor. A thermistor is a resistor that changes properties based on temperature.

Magnetic Field Sensor: While instances where you need to sense a magnetic field simply for its own sake are rare, embedding a magnet in equipment to facilitate sensory input is quite common. Home uses include attaching magnets to windows and doors to sense when one has been opened, while they are used in industry to verify that manufacturing equipment has completed a task. Sensors can take the form of a reed switch where a magnetic force opens or closes a pair of contacts inside a specially designed component, or a hall effect sensor that measures a magnet’s effect on a semiconducting material. One advantage of a hall sensor is that it can output a digital on/off signal, or can be set up to output a voltage proportional to the magnetic flux density experienced.

Load Cell: These sensors can detect force applied on an area, and are especially useful in industrial applications, where force applied to a part can mean the difference between a good product and one that doesn’t work. The most common device in use is called a strain gauge, where specially designed equipment measures the resistance of a material under load. Another method is known as piezoelectric load cell, where a material generates a voltage when deformed. One challenge with piezoelectric cells is that they only generate voltage when deformed, meaning this effect can’t be measured after the initial deformation.

Microswitch: Though we might not think of a microswitch—or any switch—as a sensor, these small mechanical devices (also known as snap-action switches) have been around since the 1930s and operate in such diverse modern technologies as arcade game buttons to automatic stops on CNC equipment. These switches use spring force to snap back to an original position when not depressed, and allow current to flow from a common connector to one of two outputs depending on the actuator position. While newer sensors have their advantages, this tried-and-true sensing method will be employed well into the future.

Sound Sensor: Sound has been used to transmit information throughout human history, and with the invention of the electronic microphone in the late 1800s—converting sound energy to mechanical motion and finally to electrical signals—this information could be recorded and transmitted. Now using increasingly powerful computers, microphones can be used to accomplish everything from coordinating lights with sound volume, to answering queries via smart devices like Amazon’s Alexa or Google Home. As speech recognition technology continues to advance, we could see this sensing method become more and more common.

Machine Vision: When we observe the world around us, no sense gives us more immediate information than sight. While our eyes do an amazing job at focusing on objects and absorbing light, the real trick lies in our brain’s ability to translate these blobs of light into something meaningful in our lives. When Cognex, a leader in machine vision, first started in the early 1980s, they celebrated when their prototype system could read the number “6” in 90 seconds. Now the company claims equipment capable of millisecond character reads—an increase in capacity of nearly 100,000 times. While this technology has leaped forward in the last 35 years, recognizing shapes, faces, and doing dimensional measurement, being able to understand what a picture truly means is still in its infancy, and will be the subject of research and advancement well into the future.

It will be exciting to see where IoT sensing technology takes us in the near future. Using microfabrication techniques, systems like an IMU that would have taken up significant space in years past can now be fit onto a single chip, allowing them to be embedded in more and more devices. Processing power to interpret input from the chips has increased exponentially, and the wireless technologies like Wi-Fi, Bluetooth and cellular data transmission have also advanced, allowing them to relay information to “the cloud” from nearly anywhere. Clearly our world will become more and more connected, hopefully leading to a bright future…or at least one where your sensor network prompts you to bring your umbrella when needed!

Zach Wendt is an engineer who enjoys writing about new technology and its impact on applications. Zach has a background in consumer product development and writes about sensors and other electronic components for Arrow Electronics.

This appears in the March (332) issue of Circuit Cellar magazine

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High-Speed Laser Range Finder Board with IMU

Integrated

The NavRanger-OEM

The NavRanger-OEM combines a 20,000 samples per second laser range finder with a nine-axis inertial measurement unit (IMU) on a single 3“ × 6“ (7.7 × 15.3 cm) circuit board. The board features I/O resources and processing capability for application-specific control solutions.

The NavRanger‘s laser range finder measures the time of flight of a short light pulse from an IR laser. The time to digital converter has a 65-ps resolution (i.e., approximately 1 cm). The Class 1M laser has a 10-ns pulse width, a 0.8 mW average power, and a 9° × 25° divergence without optics. The detector comprises an avalanche photo diode with a two-point variable-gain amplifier and variable threshold digitizer. These features enable a 10-cm × 10-cm piece of white paper to be detected at 30 m with a laser collimator and 25-mm receiver optics.

The range finder includes I/O to build a robot or scan a solution. The wide range 9-to-28-V input supply voltage enables operation in 12- and 24-V battery environments. The NavRanger‘s IMU is an InvenSense nine-axis MPU-9150, which combines an accelerometer, a gyroscope, and a magnetometer on one chip. A 32-bit Freescale ColdFire MCF52255 microcontroller provides the processing the power and additional I/O. USB and CAN buses provide the board’s high-speed interfaces. The board also has connectors and power to mount a Digi International XBee wireless module and a TTL GPS.

The board comes with embedded software and a client application that runs on a Windows PC or Mac OS X. It also includes modifiable source code for the embedded and client applications. The NavRanger-OEM costs $495.

Integrated Knowledge Systems, Inc.
www.iknowsystems.com