Today we brings news about an interesting project done by Zak Kemble , which is shared in his blog

 

Introduction

The main incentive behind this project was to see how much I could cram, in terms of both hardware and software, into a wristwatch-like device that is no larger than the display itself. An OLED display was chosen for being only 1.5mm thick and not requiring a backlight (each pixel produces its own light), but mostly because they look cool. The watch was originally going to have a 0.96″ display, but this proved too difficult to get all the things I wanted underneath it. Going up a size to 1.3″ was perfect.

                                Video

Hardware

On the hardware side the watch contains an Atmel ATmega328P microcontroller, 2.5V regulator, Maxim DS3231M RTC, 1.3″ 128×64 monochrome OLED, 2 LEDs (red and green), a buzzer sounder, 3 way switch for navigation, powered by a 150mAh LiPo battery which can be charged via USB and 2 PCBs (though one PCB is just used as a raiser for the OLED).

The ATmega328P uses its internal 8MHz oscillator and runs on 2.5V from a linear regulator. Its current draw is around 1.5mA when active and 100nA in sleep mode.

The DS3231M RTC is an excellent chip, housed in a small 8 pin package which includes a built-in temperature compensated MEMS resonator with an accuracy of ±5ppm (± 2 minutes 40 seconds per year). Only a decoupling capacitor and a few extra pull-up resistors were required. The RTC is wired up so that instead of having power applied to the VCC pin, it’s applied to the Vbat pin which reduces its current draw from around 100uA down to 2.5uA.
Unfortunately this chip seems to be very hard to get hold of at a reasonable price if you’re not in the US. I had to get mine as samples.

The battery charging circuit uses a Microchip MCP73832 along with some additional components for load sharing, where the battery can charge without the rest of the watch interfering with it.

You might have noticed in the schematic that the LEDs are directly connected to the microcontroller without any resistors. The internal MOSFETs of the microcontroller have an on resistance of around 40Ω, so with a 2.5V supply voltage and LEDs with 2V_f, around 20mA ends up through the LEDs. I would have liked to have a blue LED, but the voltage drop for those are usually more than 3V which would have required some additional resistors and a MOSFET.

As the microcontroller is running on 2.5V the battery voltage needs to be brought down a bit to obtain an ADC reading. This is done by a simple voltage divider. However, with the voltage divider connected across the battery there would be a current of around 350uA constantly flowing through it, this is a huge waste of power. A P-MOSFET (and some voltage level conversion for it, which I forgot about in the first version so it was always stuck on) was added so the divider can be turned on only when needed.

The 2.5V regulator being used is a Torex XC6206, primarily chosen for its tiny quiescent current of just 1uA.
Why a linear regulator and not a switching regulator? The switching regulators I looked at had an efficiency of at least 80% with a 2mA load, but that efficiency quickly dropped off to less than 50% with loads of 100uA. Since the devices connected to the regulator draw 2-3uA in sleep mode, a switching regulator would have performed incredibly poor compared to a linear regulator. The 2.5V linear regulator efficiency is 60% with 4.2V input going up to 83% with 3V input.

Software

So we’ve got a nice OLED display and 32KB of program space at our disposal, surely we can have more than just the time and date?

More Details Click Here

Embedded Projects Blog

AeroSky 4ch Quadcopter 

 

How To Build A Quadcopter – Choosing Hardware

 

 

In this article I will be talking about quadcopter components and how to choose them. This is part of the tutorial series on how to build a quadcopter. In the next post I will be talking about software, how to go about the algorithm and programming.
If you are planning on building a quadcopter but not sure how, this is the right place for you. Doing research is pretty boring, so I am trying to put together a comprehensive tutorial about quadcopter, hope it helps you as much as it helped me.
If you are a beginner you should also check out this beginner guide.
Building a quadcopter from scratch takes a lot of time and effort. If you are inpatient, afraid of programming/maths and has a good budget, you can just buy a pre-built kit. You could get it assembled within minutes before it’s flying (For example, like this one). But I have to say, you are missing the fun part of building a quadcopter. From choosing the parts, designing the circuits, to programming, you will be involved in every aspect of building a quadcopter, and it’s FUN!
If you have any questions, feel free to ask on this quadcopter message board.

This blog post is divided into a three parts

• What is a Quadcopter and How It Work
• Quadcopter Components Introduction
• Conclusion

What Is A QuadCopter and How It Works

A QuadCopter is a helicopter with four rotors, so it’s also known as quadrotor. Because of its unique design comparing to traditional helicopters, it allows a more stable platform, making quadcopters ideal for tasks such as surveillance and aerial photography. And it is also getting very popular in UAV research in recent years.
The Quadcopters exist in many different sizes. From as small as a CD up to something as big as one meter in width.

 

On a regular helicopter has one big rotor to provide all the lifting power and a little tail rotor to offset the aerodynamic torque generated by the big rotor (without it, the helicopter would spin almost as fast as the propeller)
Unlike a helicopter, a quadrotor has four rotors all work together to produce upward thrust and each rotor lifts only 1/4 of the weight, so we can use less powerful and therefore cheaper motors. The quadcopter’s movement is controlled by varying the relative thrusts of each rotor.
These rotors are aligned in a square, two on opposite sides of the square rotate in clockwise direction and the other two rotate in the opposite direction. If all rotors turn in the same direction, the craft would spin would spin just like the regular helicopter without tail rotor. Yaw is induced by unbalanced aerodynamic torques. The aerodynamic torque of the first rotors pair cancelled out with the torque created by the second pair which rotates in the opposite direction, so if all four rotors apply equal thrust the quadcopter will stay in the same direction.

 

To maintain balance the quadcopter must be continuously taking measurements from the sensors, and making adjustments to the speed of each rotor to keep the body level. Usually these adjustments are done autonomously by a sophisticated control system on the quadcopter in order to stay perfectly balanced. A quadcopter has four controllable degrees of freedom:Yaw, Roll, Pitch, and Altitude. Each degree of freedom can be controlled by adjusting the thrusts of each rotor.

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Flutter is an open source ARM-powered wireless Arduino with 1000m+ (3200 ft) range and 256-bit AES hardware encryption.

What is Flutter?

Flutter is a wireless electronics development platform based on Arduino. With over 3200ft (1km) of usable range, a powerful ARM processor, and integrated encryption, Flutter makes it easy for you to build projects that communicate across the house, across the neighborhood, and beyond.
Whether you want to check the temperature of a beer-brewing setup, have your mailbox send you a text message when the mailman arrives, control a swarm of flying robots, or just turn on your lights with your phone, Flutter gives you the range, power, and flexibility to do it.
We’re not just building circuit boards though. Our goal is simple: make it easier for engineers, makers, builders, and hackers to go farther with their projects than ever before. Even if it's their first time. We’re going to arrange and keep a set of basic electronics tutorials so getting started with Flutter is as easy as possible.


 

What is Flutter?

Flutter is a wireless electronics development platform based on Arduino. With over 3200ft (1km) of usable range, a powerful ARM processor, and integrated encryption, Flutter makes it easy for you to build projects that communicate across the house, across the neighborhood, and beyond.
Whether you want to check the temperature of a beer-brewing setup, have your mailbox send you a text message when the mailman arrives, control a swarm of flying robots, or just turn on your lights with your phone, Flutter gives you the range, power, and flexibility to do it.
We’re not just building circuit boards though. Our goal is simple: make it easier for engineers, makers, builders, and hackers to go farther with their projects than ever before. Even if it's their first time. We’re going to arrange and keep a set of basic electronics tutorials so getting started with Flutter is as easy as possible.

Getting Connected

Creating Flutter networks is easy, even if it’s just two boards. Specify networks in Arduino code or configure Flutter with our mobile app. Once configured, devices can enter and exit the network seamlessly. This makes it extremely easy to set up a network at home (or anywhere else) where all of your projects can reliably communicate. Flutter is like a second network for your devices.
Multiple options
Building wireless projects shouldn’t have to be expensive. Flutter was built from the ground up with cost in mind, that’s why our boards start at just $20. We’ve worked hard to keep costs as low as possible and deliver you a quality product you can afford to use in as many projects as you’d like. To accomplish this, we're designing two boards:

Flutter Basic ($20)
   Still under development, the Flutter basic is tiny and simple. You get all the features of Flutter (including 1km range) in a circuit board with an low-profile integrated antenna, rather than the large antenna shown in the video. Featuring micro USB for power and programming, components on both sides to reduce size, an LED, and a button, as well as plenty of digital and analog I/O.
Flutter Pro ($30)
Prototypes of this board are what is shown in our video. The Flutter Pro adds battery charging, a professional screw mount antenna, an additional button, and more memory for more code.

  

Shields

We've designed a handful of shields for Flutter, focused on getting started and connecting networks. Every Flutter board that ships comes with our Breakout board and socket headers.

Breakout Board

The Flutter Breakout board is basically a socket for your Flutter Board, letting you build projects you can easily remove Flutter from. This is great for projects you don't use all the time! Every board ordered comes with at least one of these breakouts (with sockets) so you can get going quickly!

RC Shield

The RC shield makes it easy to hook up Flutter to a standard hobby R/C car like the one shown in the video (just two plugs, no soldering). 

It's not just for remote control cars though, the RC shield features a buzzer, DC jack, a few FETs for switching things on, plugs for 4 R/C servos (for use with quads), and a temperature sensor.

The FET switches on the board allow you to easily control LED lights (say, headlights and tail lights for a car), or just turn on a solenoid valve for watering the plants.

Features

• 1,000+ meter range
• 1.2 Mbps* max data rate
• 915 MHz operating frequency
• Atmel SAM3s ARM CPU at 64MHz
• Cryptographic key storage
• Mesh networking
• 3.3v system voltage
• 10-40mA current draw (normal use)

 

One of the most important features of any wireless system is its range and reliability. We use wifi every day, but take a few steps down the driveway and coverage quickly becomes scarce. Flutter is a different kind of wireless system, completely self-contained with over a half-mile range. This allows for a wireless platform without borders, and no longer being chained to a router means your projects are free to follow you out the front door, through the yard, and down the street.

Security
As with any wireless device, security is extremely important. Since information leaving your antenna can be picked up by anyone nearby (and information coming into your antenna could have come from anywhere) it’s important to have a system in place that verifies who you are talking to in a secure way that’s also easy to use.
To make Flutter as secure as possible, we’re building in special cryptographic hardware and integrating cryptography into every layer of the software, giving the user ultimate control over who can and cannot communicate with their devices.
Integrated Cryptography
In addition to software for handling encryption and decryption of data, flutter uses the cryptographic chip as the hardware element of the security system. Built specifically for use in high security applications, the Atmel ATSHA204 is based around secure storage for protecting your encryption keys.
Using the chip’s features, Flutter networks are able to use extremely strong encryption and other cryptographic techniques to keep your network secure.
Open Source
Flutter’s goal will always be to provide the community with access to inexpensive and reliable wireless technology, and so Open Source was a natural marriage for our project. Every aspect of our system will be made available, from schematics, board designs, the bill of materials, right down to the firmware and mobile app. We want to make it as easy as possible for you to build or improve upon our foundation. 
Mesh Networking
Flutter’s wireless technology seamlessly routes messages across multiple devices to reach their final destination. Want to send lots of data across longer distances? Drop another Flutterboard in between and let Flutter handle the rest. Got an ambitious project that requires a huge network? We’ve got you covered there, too. Flutter is designed to scale from two devices to thousands, and our flexible tagging system means you won’t lose track between the lights in your bedroom and the lights in the kitchen.
Versatility & Mobile
Flutter easily connects to other computer networks either via USB to a PC or many modern Android phones, over wifi or ethernet with our Flutter Network Shield, or over bluetooth with our Bluetooth Shield. Bluetooth is especially useful with mobile since it allows your phone to connect directly to the Flutter network without requiring Internet access or a wifi router.
Flutter’s direct USB capability and our comprehensive set of shields means that no matter what you build with Flutter it’s always possible to communicate with the network using your phone.
We plan to develop a free, open source mobile app to provide users with an easy way to configure alerts and display project data on their phone. Use buttons and sliders to send commands to any device or browse and edit your network configuration and device tags, Flutter makes it extremely easy to manage multiple devices.

Potential Applications

You love finding innovative ways to take on everyday tasks, whether it’s dimming your lights with your smartphone, getting text notifications when the doorbell rings or the mail arrives, or even building your own quadcopter. Whatever the task at hand you can rely on Flutter to be versatile and robust enough to take on the challenge:
 

Light, Water, and Temperature Sensors
By connecting simple sensors with Flutter you can easily collect environmental data like temperature or light, water, and humidity levels. Which means you can do anything from measuring the humidity in your greenhouse, to building a wireless beer brewing setup, monitoring the temperature in your grill, monitoring sunlight for solar applications, or even checking the Ph levels in your pool. And that’s just with a couple cheap sensors.
Quadcopters
With its powerful CPU and long range radio, Flutter is an excellent platform for building quadcopters. Flutter’s protocol is designed just as much for reading a few sensors as it is for hardcore robotics applications so the user has ultimate control over what the protocol is doing.
Self-Diagnosis and Spectrum Analyzer
Flutter can even be used to diagnose itself. Because Flutter has bare metal access to the radio hardware, you can easily listen to the radio waves around you and plot the data. We'll even build some of this functionality into the app for basic diagnosis.
RC Cars
Hooking up Flutter to an RC car is dead simple. Whether you just want to drive it with an SNES controller for fun or use it for swarm robotics research, Flutter makes it easy.

 Images and Details
Courtsey

Via Kick Starter

Source: Flutter Wireless