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LimiFrog- A STM32-L4 based wearable device with bluetooth and sensors

Posted on September 9, 2015 by R-B One comment

Xavier Cauchy introduces LimiFrog– an ultra-compact, Bluetooth-enabled, and multiple sensor-packed development board based on the powerful STM32-L4 microcontroller. The board weighs less than 25 grams and features a 160×128 color OLED display, 8MB data flash, 500 mAH LiPo battery, USB connectivity, and lots of sensors, which include temperature, pressure, light, sound, accelerometer, gyroscope, and magnetometer.

LimiFrog development board

Arduino Mini weather station

Posted on September 3, 2015 by R-B Leave a comment

Matej Blagšič posted instructions for building a Bluetooth-enabled Arduino-based mini weather station that can measure ambient temperature, pressure and humidity.

Arduino mini weather station

The main question is why did I/we choose the Seeeduino V4. If we were going for a cheap Chinese alternative, we could have gone with Funduinos or anything like that, as the Seeeduino is only a few bucks cheaper. The answer is the features. I see it as an upgrade to the Arduino Uno. It has all the features labeled with arrows. Some are subtle like the micro USB port, as many of us have smart phones that uses the same plug, option for soldering male headers parallel to female ones and the convenience of the already built in ports form I2C and serial data.

The major ones are really blessed by me. The 3.3V – 5V logic switch is priceless because so many arduino peripherals and mostly sensors work with 3.3V. I wasn’t aware about this a few years ago, as 5V stood to me as a standard but really a lot of sensors work with 3.3V and the most of 5V ones can operate with that voltage without any problem. Refer to the sensors datasheet for that information.

This board will work on 3.3V great with one of our I2C sensor and the other one that operates with 5V. Also some of the bluetooth modules work with 5V, but the logic works with 3.3V. I will address this topic in the bluetooth step of this tutorial.

3D compass to visualize Earth’s magnetic field

Posted on September 2, 2015 by R-B Leave a comment

John Leeman’s 3D compass is a very interesting way of visualizing the 3D orientation of the Earth’s magnetic field at a particular location. It uses Arduino Uno, NeoPixel rings, and HMC5883L Magnetometer.

3D compass

DIY USB power meter stick

Posted on September 2, 2015 by R-B 2 comments

Electro-Labs has posted a new project about making a DIY USB power meter based on Atmega328 processor. It sits between the USB port of the computer and the USB device to be connected to monitor the USB output supply voltage and the current drawn by the USB load device. The computed power consumption is displayed on a small OLED on the board. The USB meter stick itself gets powered from the USB port.

DIY USB power meter stick

The board is built around an Atmel ATMEGA328 microcontroller. To make the circuit as small as possible, the MCU is used in minimal configuration. Internal 8MHz oscillator is used. The voltage and the current are measured by the internal 10 bit ADC. To make the measurements more accurate, an external 2.5V voltage reference IC, Microchip MCP1525 is included. The current is converted to voltage on a 0.01R sense resistor and precisely amplified by LT6106 before read. The stick can measure up to 2.5A. Since the OLED display requires 3.3V supply voltage, L78L33ACUTR linear voltage regulator is used for 5V to 3.3V conversion.

Controlling servos with hand motion

Posted on August 26, 2015 by R-B One comment

Justin Platz and Kurt Clothier from Pubnub illustrates how to control a physical object with the motion of two hands. They used Raspberry Pi and the Leap Motion controller for this purpose.

Controlling servos with hand motion

The two servos mirror the movement of the user’s two individual hands. Attached to the servos are 8×8 RGB LED Matrices, which react to each finger movement on your hand. The Leap Motion communicates directly with the Raspberry Pi via PubNub Data Streams with minimal latency, and the Raspberry Pi then drives the servos.

Leap Motion is a powerful device equipped with two monochromatic IR cameras and three infrared LEDs. In this project, the Leap Motion is just going to capture the pitch and yaw of the user’s hands and publish them to a channel via PubNub. Attributes like pitch, yaw and roll of hands are all pre-built into the Leap Motion SDK.

To recreate realtime mirroring, the Leap Motion publishes messages 20x a second with information about each of your hands and all of your fingers to PubNub. On the other end, our Raspberry Pi is subscribed to the same channel and parses these messages to control the servos and the lights.

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