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Nocturnal hypoglycaemia detector

Posted on October 12, 2016 by R-B Leave a comment

Hypoglycaemia is a condition characterized by an abnormally low level of glucose in blood. It is associated with diabetes, and is likely to occur if someone with diabetes takes too much insulin, eats less than usual, or exercises too hard. Novirium‘s Nighttime Hypoglycaemia monitor is a bluetooth-enabled device that acts as a safety net for type 1 diabetics, while they’re sleeping. The nighttime hypoglycemia results in excessive sweating. This monitor measures the skin temperature and humidity to detect severe nocturnal hypoglycaemic events. Measurements are taken periodically and are sent to a nearby Android phone via Bluetooth. If such an event is detected, a list of emergency contacts are called for assistance.

Nighttime hypoglycemia monitor

A mobile sensor device contains an ATmega328p, an HIH6131 humidity and temperature sensor, a LIS3LV accelerometer and a SPBT2632C2A Bluetooth module, all powered by a 2.7V LTC4081 switchmode power supply/charger and a 400mAh LiPo battery. The sensor is designed to be worn close to the skin of the diabetic, and detect the heavy sweating that often occurs with very low blood glucose levels.

Every 15 minutes, the sensor module powers up the Buetooth module and connects to the nearby Android phone, uploading all the sensor data for that period before switching the Bluetooth back off to save power. The Android application then sorts through this data, and determines if an alarm is required. If an alarm is triggered, it then works through a list of preset contacts, calling them for assistance until one texts back.

Filter optimization for A/D conversion

Posted on October 12, 2016 by R-B Leave a comment

Filters are necessary to eliminate unwanted noise or distortion in a signal prior to any A/D conversion process. Designing a filter to pass the desired frequencies is easy, but it introduces signal loss, or insertion loss. Check out this application note from TI for some useful tips to optimize the filter design to minimize the losses.

Filter insertion losses

One of the first steps of filter optimization is the selection of the center frequency and the bandwidth of the filter. Once this step has been completed the task becomes one of putting the filter elements on the printed circuit board (PCB). PCB design is critical to filter performance, but even before we get to this stage we usually select both the component values and the component sizes we would like to use, this way we can allocate PCB space for the various components. As will be described later, it is very important to choose the filter components first, then make the necessary space available on the PCB, rather than trying to squeeze your filter into the space you have left at the end of the design. The components selected will be critical to the performance of your filter.

CastMinder detects complications in orthopedic casts/splints

Posted on October 11, 2016 by R-B Leave a comment

Alex Wulff’s CastMinder is a Bluetooth-enabled sensor system designed to predict complications in orthopedic casts and splints. It is capable to detect conditions associated with the onset of complications, including skin infection, skin irritation, bleeding, and something called compartment syndrome, where an excess of pressure can lead to circulation loss in the casted limb.

CastMinder can detect complications in orthopedic casts and splints while healing patients faster and with less pain.

The primary devices in the CastMinder system are tiny sensor nodes embedded inside of a cast or splint. These sensor nodes continuously collect data and dump it via Bluetooth to an iOS application which serves as the brains of the entire network. These small nodes are equipped with a variety of sensors, such as a pressure sensor to detect compartment syndrome, a temperature sensor to detect patient fevers, and a moisture sensor to detect skin bleeding and irritation. Other devices worn on the cast use electrical stimulation to lessen patient pain and stimulate bone growth. The entire system is controlled by the CastMinder iOS app, which can both analyze data to future conditions and alert physicians, nurses, patients, and more to potentially harmful changes in the status of the cast.

Universal motor driver for PIC16F MCUs

Posted on October 11, 2016 by R-B One comment

This application note from Microchip presents the design of an open-loop speed control TRIAC-driven universal motor driver board. An interesting thing about this design is it uses Core Independent Peripheral (CIP) on an 8-bit microcontroller to optimize the processing speed and free up the CPU usage. The complete source code and reference design material are included.

Block diagram of motor controller

The universal motor used in this application note runs from 120V-240V AC power and is driven from a TRIAC. A bench test for running a 220V universal motor has been done. The circuit is powered off the line from an non-isolated AC supply; therefore, safety precautions should be taken when working with this type of system. An isolated on-board UART connection is available for debugging on a live circuit. The low-cost design and its type of motor are suitable for high-torque motor applications commonly used in blenders, food processors, drills and other home appliances.

As shown in Figure 2, the system consists of an AC supply as an input to a passive EMI filter. A selectable capacitive or resistive power supply creates a DC voltage for the microcontroller and its associated input controls. An isolated UART bridge connects to the microcontroller for debug purposes.
A single potentiometer (POT) controls the firing angle of the TRIAC. The Zero-Cross Detection (ZCD) hardware module provides the required synchronization. The TRIAC is pulse driven from multiple pins on the PIC16F1618. A few LEDs indicate the firing angle. A momentary switch toggles the motor ON or OFF.

16×32 RGB panel + Arduino Shield are now also available at Elecrow

Posted on October 10, 2016 by R-B 2 comments

Our Chinese partner, Elecrow, now also carries our 16×32 RGB LED matrix panel + Arduino driver shield. They also offer worldwide shipping at much lower costs.

The RGB matrix panel has 512 bright RGB LEDs arranged in 16 rows and 32 columns. Row and column driver circuits are built on the back side of the matrix panel. The data and control signal pins are accessible through a HUB75 (8×2 IDC) connector. It requires 12 digital I/O pins of Arduino Uno for full color control. The display module also comes with a RGB connector shield for Arduino Uno and necessary cables for easy wiring between the RGB panel and the Arduino board.

It also features the DS1307 RTC chip on board along with a CR1220 coin-cell battery holder. The I2C pins of the DS1307 chip are pre-wired to A4 and A5 pins of the shield.

Buy it from our Elecrow Store

Click here for hookup guide

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