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

Gesture Recognition in a Boxing Glove

Sensors Packed in the Punch

Learn how these two Boston University graduate students built a gesture-detection wearable that acts as a building block for a larger fitness telemetry system. Using a Linux-based Gumstix Verdex, the wearable couples an inertial measurement unit with a pressure sensor embedded in a boxing glove.

By Blade Olson and Patrick Dillon

Diagnostic monitoring of physical activity is growing in demand for physical therapists, entertainment technologists, sports trainers and for postoperative monitoring with surgeons [1][2]. In response to the need for a low-cost, low-profile, versatile, extensible, wearable activity sensor, the Hit-Rec boxing sensor is a proof-of-concept device that demonstrates on-board gesture recognition and high-throughput data monitoring are possible on a wearable sensor that can withstand violent impacts. The Hit-Rec’s ability to gather raw sensor values and run calculations at a high frame rate make the Hit-Rec an ideal diagnostic device for physical therapists searching for slight perturbations across a user’s gestures in a single recording session or for looking at discrepancies between the ideal motions of a healthy individual and the user’s current motions. The following sections will describe the implementation of a prototype for the Hit-Rec using a boxing glove (See Lead Photo Above).

SYSTEM OVERVIEW

The Hit-Rec sensor incorporates a Gumstix Verdex Pro running Linux, a 9-DoF (degree of freedom) inertial measurement unit (IMU), a pressure sensor that is connected to the Gumstix via a 12-bit analog-to-digital converter (ADC) and LEDs for user feedback. The ADC and IMU both communicate over I2C. The LEDs communicate to the Gumstix through general purpose input/output (GPIO). Figure 1 shows a high-level explanation of hardware interfaces and Figure 2 provides an illustration of the system overview. All software was written in C and runs exclusively on the Gumstix Verdex Pro. A Linux kernel module was written to interact with the LEDs from the user-space program that performs data capture and analysis. IMU data was smoothed and corrected in real-time with an open-source attitude and heading reference system (AHRS) provided by Mahony [3][4]. A circular buffer queue was used to store and retrieve sensor data for recording and analysis. Punch classification compares accelerometer values at each data point and chooses the gesture with smallest discrepancy.

Figure 1
This high-level diagram details the data transfer connections made between the main hardware and software components of the Hit-Rec.

Figure 2
Overview of the software architecture for translating IMU and Pressure data to user feedback

Each of three LEDs on the Hit-Rec glove represents a different gesture type. After the “punchomatic” program is started, the user is prompted to record three gestures by way of three flashing LEDs. In the background, IMU data is continuously being recorded. The first, yellow LED flashes until an impact is registered, at which point the last 50 frames of IMU data are used as the “fingerprint“ for the gesture. This gesture fingerprint is stored for the rest of the session. Two additional gestures are recorded in an identical manner using the red and blue LEDs for the subsequent punches. After three gestures have been recorded, the user can punch in any form and the Hit-Rec will classify the new punch according to the three recently recorded punch gestures. Feedback on the most closely related punch is presented by lighting up the corresponding LED of the originally recorded gesture when a new punch occurs.

SENSORS

We used the Adafruit LSM9DS0 with breakout board as an IMU sensor and a force-sensitive resistor (FSR) from Adafruit as a pressure sensor. Both sensors communicate over I2C, which the pressure sensor achieves through an ADC. …

Read the full article in the June 335 issue of Circuit Cellar

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Scalable Wearable Development Kit

ON Semiconductor recently announced the availability of a new Wearable Development Kit (WDK1.0). The kit comprises the following: a touchscreen display; wired and AirFuel-compatible wireless charging capability; a six-axis motion sensor and temperature sensor; an alarm, timer, and stopwatch; schematics; firmware and sample code; a dock station for charging; and a downloadable SmartApp for evaluating and controlling the smartwatches multiple functions.OnSemi Wearable Dev Kit

The WDK1.0’s features, specs, and benefits:

  • NCP6915 power Management IC provides five LDOs and one DC-DC
  • NCP1855 battery charger IC, an LC709203F fuel gauge, and a 10-W rated SCY1751 wireless charging front-end controller
  • MEMS-based FIS1100 IMU, with three‐axis gyroscope and three‐axis accelerometer operation for multidimensional motion tracking
  • Embedded temperature sensor included and an LC898301 driver IC for initiating haptic feedback
  • nRF52832 multi-protocol system-on-chip (SoC)
  • Eclipse-based IDE
  • 1.44″ 128 × 128 pixel TFT display with a capacitive touch screen
  • 26‐pin expansion port

Source: ON Semiconductor

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