Simple negative resistance oscillators

Bob tipped us about a simple oscillator that uses negative resistance:

Normally -according to the Ohm’s law– when the applied voltage is increasing, the current is increasing too, however some components can break this law. When the voltage increases, current decreases. This is called negative resistance.

One of the most know element that exhibits this behavior is a tunnel diode. Once very promising, today it isn’t widely used in popular designs and occupies a niche in microwave applications. It’s a bit challenging to get one, fortunately simple circuits that have negative resistance feature can be build from popular discrete elements. One of them I will present today.

Simple negative resistance oscillators – [Link]

Stay Connected While Travelling Without Fees With VoxEra

Mobile Roaming allows you to stay connected wherever you are and receive calls and SMSs, but with very expensive cost. So if you don’t have enough budget, you will lose your incoming calls till you are back from a travel.

A team of innovators from Egypt had developed a new device called “VoxEra” that enables you to stay connected when travelling without using roaming service. Simply, all you have to do is to put your SIM card into VoxEra and connect it to the internet, install VoxEra App into your smartphone and enjoy calling and texting with a high quality connection.

Compared with other similar products, VoxEra uses a standard GSM network instead of VoIP service, which mean that other people don’t have to install any application to connect with them. It will also use your own SIM card with the same mobile number and will give you more options forward to record incoming calls when you are offline.

Think of VoxEra as a message converter; when you receive a call, VoxEra receives a GSM call and then converts it into a VoIP call. Then, it sends that converted message to the Cloud through the Internet. In the same way, while making a call, VoxEra sends a message through the Cloud. When the device receives the message, it converts it into a GSM call, at which point, it is delivered to the number you’ve dialed.

The voice roaming killer is now live on Kickstarter and has already reached a $28K fund! Super early bird edition is still available for $79. After the campaign, the device will be available for $119 with free shipping worldwide.

Pixel 2.0, Arduino Zero-Like Board With Smart Display

The Pixel is an Arduino-compatible smart display, combining a 32-bit Cortex M0+ MCU with 32K of RAM, a 1.5″ 128×128 color OLED screen, and a microSD slot all in one package.

This is Rabid Prototypes’ second iteration of Pixel, which originally raised nearly $10,000 on Kickstarter back in 2015. The board offers a number of potential use cases, ranging from wearable devices, to sensor data monitors, to retro video game consoles.

The Pixel is compatible with Arduino’s SPI and SD libraries, as well as Adafruit’s graphics library, which provides functions for blitting images, drawing primitives like lines and circles, and even includes bitmapped font support.

Additionally, if you ever need to modify the fuses or bootloader, the Pixel features a standard SWD header that can be used with Microchip’s Atmel-ICE development tool.

Here are the technical specifications of Pixel:

  • Microcontroller: Atmel ATSAMD21G18 ARM Cortex M0+
  • Clock speed: 48 MHz
  • Operating voltage: 3.3V
  • I/O pin limits: 3.3V, 7 mA
  • Digital I/O pins: 14, with 12 PWM
  • Analog input pins: 6, 12-bit ADC channels
  • Analog output pins: 1, 10-bit DAC
  • Flash memory: 256 KB
  • SRAM: 32 KB
  • Voltage regulator: 3.7V – 5.5V input / 3.3V, 300mA output
  • PCB Dimensions: 1.8 x 1.8″ (46mm x 46mm)
  • Display : 128×128 16-bit color 1.5″ (38mm) OLED w/ SSD1351 driver

Pixel is now live on Kickstarter! you can get your own Pixel 2.0 for $75 or two for only $135. The campaign still has 12 days to go, check its video to know further details about Pixel 2.0:

Source: Hackster Blog

 

Raspberry Pi I2C LCD Set Up and Programming

In this video Circuit Basics show us how to use I2C to connect an LCD to the Raspberry Pi. After showing you how to connect the LCD to the Pi with a PCF8574 (http://www.circuitbasics.com/pj6v), they show you how to program it. First I’ll cover the basic stuff like printing text to the screen, clearing the screen, blinking text, and positioning text. Then I’ll go into more advanced stuff like scrolling text, printing data from a sensor, turning on and off the cursor, and printing custom characters.

Raspberry Pi I2C LCD Set Up and Programming [Link]

Motion sensor offers low-power settings

Susan Nordyk @ edn.com writes:

Small enough for wearable devices, STMicroelectronics’ LIS2DW12 three-axis accelerometer draws only 50 nA in standby mode and 380 nA in low-power mode at a 1.6-Hz output data rate, adding negligible load on the battery. Operating from a supply voltage of 1.62 to 3.6 V, the LIS2DW12 enables extended operation from small coin or button cells.

Motion sensor offers low-power settings – [Link]

Full-360˚ angle sensor ICs

by Graham Prophet @ edn-europe.com:

Allegro MicroSystems has added two 0˚ to 360˚ angle sensor ICs that provide contactless high-resolution angular position information based on magnetic Circular Vertical Hall (CVH) technology. Allegro has incorporated advanced diagnostics to support safety-critical automotive and industrial uses.

Simple 3 phase Arduino energy meter

Simple 3 Phase Arduino energy meter from The DIY Life:

Again, with this meter I was going for simplicity. Sure, for perfectly accurate measurements you need to measure both the supply current and voltage but for this application and in the interests of keeping the energy meter simple and safe – only requiring a non-contact connection to your mains – I’ve decide to stick with a simple current measurement which gives you an estimate to within a couple of decimal points of a kilowatt hour.
This meter measures the supply current through each phase using a CT (current transformer) and then does a few calculations to give you the current, power, maximum power and kilowatt hours consumed for each phase.

Simple 3 phase Arduino energy meter – [Link]

IoT based remote heart rate monitoring system

With the advent of IoT technologies and decreasing cost of wireless sensors, the use of remote healthcare monitoring systems is growing rapidly, thereby allowing health care access to more people at affordable costs. To illustrate the concept of IoT based patient monitoring, Raj from Embedded Lab has shared a project article on how to build a remote heart rate monitoring system using ESP8266 and Easy Pulse sensor. The project uses a TFT LCD to display heart beat rate and PPG waveform locally, as well as uploads the pulse rate to a Google spreadsheet for accessing the data from remote. The Google sheet’s Chart  feature allows the remote user to visually track the pulse rate variation over time.

Pulse rate and PPG waveform displayed locally on a TFT LCD
Pulse rate chart for remote access

Read details of the project here! 

Thermohygrometer with clock and LCD display on Arduino UNO

techrm @ instructables.com has a tutorial on a nice thermohydrometer:

These 7 steps will drive you through the “construction” of a thermo-hygrometer with clock on Arduino UNO.

Data and time, humidity and temperature will be shown on a LCD 16×2 display .If you have purchased a LCD display and want to know how to properly solder a pin header to it, take a look at our tutorial “Yet another tutorial on how to solder”.

Each step of this tutorial is independent from the others. So, if you are looking for an easy way to make your DS3231 work (for example) this tutorial is also suitable for you.

Thermohygrometer with clock and LCD display on Arduino UNO – [Link]