Gyrosensors

Gyro sensors, also known as angular rate sensors or angular velocity sensors, are devices that sense angular velocity.

Angular velocity

In simple terms, angular velocity is the change in rotational angle per unit of time.
Angular velocity is generally expressed in deg/s (degrees per second).

Gyro Sensor Types

Gyro sensors come in a variety of types. Here, different types are plotted by size and performance.

 

In recent years vibration gyro sensors have found their way into camera-shake detection systems for compact video and still cameras, motion sensing for video games, and vehicle electronic stability control (anti-skid) systems, among other things.

Moving forward, demand for vibration gyros is expected to grow in areas such as vehicle driver safety and support systems, and in robot motion control.

Vibration Gyro Sensors

Vibration gyro sensors sense angular velocity from the Coriolis force applied to a vibrating element. For this reason, the accuracy with which angular velocity is measured differs significantly depending on element material and structural differences. Here, we briefly describe the main types of elements used in vibration gyro sensors.

Types of elements used in vibration gyro sensors

Vibration gyro sensor manufacturers are using a variety of materials and structures in an effort to devise compact, high-accuracy gyro sensors that have good characteristics, including: 
 · scale factor
 · temperature-frequency coefficient
 · compact size
 · shock resistance
 · stability
 · noise characteristics

	Material	Sample Structure
Piezoelectric transducer
	Ceramic
Silicon transducer	Silicon	Si MEMS NOTE: Every company uses a different structure.

How Angular Velocity Sensing Works (in Vibration Gyro Sensors)

Vibration gyro sensors sense angular velocity from the Coriolis force applied to a vibrating object.
Here, we explain how this works, using as an example Epson 's double-T structure crystal element.

1. Normally, a drive arm vibrates in a certain direction.		2. Direction of rotation		3. When the gyro is rotated, the Coriolis force acts on the drive arms, producing vertical vibration.
		5. The motion of a pair of sensing arms produces a potential difference from which angular velocity is sensed. The angular velocity is converted to, and output as, an electrical signal.		4. The stationary part bends due to vertical drive arm vibration, producing a sensing motion in the sensing arms.

Gyro Sensor Applications

There are three main applications for gyro sensors.

Sense the amount of angular velocity produced.

Used in measuring the amount of motion itself.

Ex.) Checking athletic movement

Senses angular velocity produced by the sensor's own movement. Angles are detected via integration operations by a CPU.

The angle moved is fed to and reflected in an application.

Ex.) Car navigation systems
Game controllers
Cellular

Senses vibration produced by external factors, and transmits vibration data as electrical signals to a CPU.

Used in correcting the orientation or balance of an object.

Ex.) Camera-shake correction
Vehicle control

Interesting facts
Examples of angular velocity in applications:
 · Car navigation systems: ~10 deg/s
 · Vehicle control: ~30 deg/s
 · Camera-shake correction: ~100 deg/s
 · Game controllers: ~300 deg/s
 · Sensing the swing of golf's top players: ~3,000 deg/s

Raspberry Pi

The normal computing world has gone smaller unlike the old times when a single computer spanned across a whole room. In the 21st century the most recent and groundbreaking invention in the field of computing is that of the "Raspberry pi".

The Raspberry Pi is a credit-card sized computer that plugs into your TV and a keyboard. It is a capable little computer which can be used in electronics projects, and for many of the things that your desktop PC does, like spreadsheets, word-processing and games. It also plays high-definition video. We want to see it being used by kids all over the world to learn how computers work, how to manipulate the electronic world around them, and how to program.

Specifications

	Model A	Model B	Model B+
Target price:	US$25	US$35
SoC:	Broadcom BCM2835 (CPU, GPU, DSP, SDRAM, and single USB port)
CPU:	700 MHz ARM1176JZF-S core (ARM11 family, ARMv6 instruction set)
GPU:	Broadcom VideoCore IV @ 250 MHz OpenGL ES 2.0 (24 GFLOPS) MPEG-2 and VC-1 (with license]), 1080p30 h.264/MPEG-4 AVC high-profile decoder and encoder
Memory (SDRAM):	256 MB (shared with GPU)	512 MB (shared with GPU) as of 15 October 2012
USB 2.0 ports:[	1 (direct from BCM2835 chip)	2 (via the on-board 3-port USB hub)	4 (via the on-board 5-port USB hub)
Video input:	15-pin MIPI camera interface (CSI) connector, used with the Raspberry Pi Camera Addon
Video outputs:	Composite RCA (PAL and NTSC) –in model B+ via 4-pole 3.5 mm jack, HDMI (rev 1.3 & 1.4),[raw LCD Panels via DSI 14 HDMI resolutions from 640×350 to 1920×1200 plus various PAL and NTSC standards.
Audio outputs:	3.5 mm jack, HDMI, and, as of revision 2 boards, I²S audio (also potentially for audio input)
Onboard storage:	SD / MMC / SDIO card slot (3.3 V card power support only)		MicroSD
Onboard network:	None	10/100 Mbit/s Ethernet (8P8C) USB adapter on the third/fifth port of the USB hub
Low-level peripherals:	8× GPIO,UART, I²C bus, SPI bus with two chip selects, I²S audio +3.3 V, +5 V, ground		17× GPIO
Power ratings:	300 mA (1.5 W)	700 mA (3.5 W)	600 mA (3.0 W)
Power source:	5 V via MicroUSB or GPIO header
Size:	85.60 mm × 56 mm (3.370 in × 2.205 in)– not including protruding connectors
Weight:	45 g (1.6 oz)

History :

In 2006, early concepts of the Raspberry Pi were based on the Atmel ATmega644 microcontroller. Its schematics and PCB layout are publicly available.Foundation trustee Eben Upton assembled a group of teachers, academics and computer enthusiasts to devise a computer to inspire children. The computer is inspired by Acorn's BBC Micro of 1981.Model A, Model B and Model B+ are references to the original models of the British educational BBC Micro computer, developed by Acorn Computers.The first ARM prototype version of the computer was mounted in a package the same size as a USB memory stick.It had a USB port on one end and an HDMI port on the other.

The Raspberry Pi Components :

The Raspberry Pi device looks like a motherboard, with the mounted chips and ports exposed (something you'd expect to see only if you opened up your computer and looked at its internal boards), but it has all the components you need to connect input, output, and storage devices and start computing.

You'll encounter two models of the device:Model A and Model B. The only real differences are the addition of Ethernet and an extra USB port on the more expensive Model B.

Here are the various components on the Raspberry Pi board:

• ARM CPU/GPU -- This is a Broadcom BCM2835 System on a Chip (SoC) that's made up of an ARM central processing unit (CPU) and a Videocore 4 graphics processing unit (GPU). The CPU handles all the computations that make a computer work (taking input, doing calculations and producing output), and the GPU handles graphics output.
• GPIO -- These are exposed general-purpose input/output connection points that will allow the real hardware hobbyists the opportunity to tinker.
• RCA -- An RCA jack allows connection of analog TVs and other similar output devices.
• Audio out -- This is a standard 3.55-millimeter jack for connection of audio output devices such as headphones or speakers. There is no audio in.
• LEDs -- Light-emitting diodes, for all of your indicator light needs.
• USB -- This is a common connection port for peripheral devices of all types (including your mouse and keyboard). Model A has one, and Model B has two. You can use a USB hub to expand the number of ports or plug your mouse into your keyboard if it has its own USB port.
• HDMI -- This connector allows you to hook up a high-definition television or other compatible device using an HDMI cable.
• Power -- This is a 5v Micro USB power connector into which you can plug your compatible power supply.
• SD cardslot -- This is a full-sized SD card slot. An SD card with an operating system (OS) installed is required for booting the device. They are available for purchase from the manufacturers, but you can also download an OS and save it to the card yourself if you have a Linux machine and the wherewithal.
• Ethernet -- This connector allows for wired network access and is only available on the Model B.

Many of the features that are missing, such as WiFi and audio in, can be added using the USB port(s) or a USB hub as needed. Next: More details on the device itself and its compatible operating systems.

Accelerometers

An accelerometer is a device that measures proper acceleration ("g-force"). Proper acceleration is not the same as coordinate acceleration (rate of change of velocity). For example, an accelerometer at rest on the surface of the Earth will measure an acceleration g= 9.81 m/s² straight upwards. By contrast, accelerometers in free fall orbiting and accelerating due to the gravity of Earth, will measure zero.

Accelerometers have multiple applications in industry and science. Highly sensitive accelerometers are components of inertial navigation systems for aircraft and missiles. Accelerometers are used to detect and monitor vibration in rotating machinery. Accelerometers are used in tablet computers and digital cameras so that images on screens are always displayed upright. Accelerometers are used in drones for flight stabilisation. Pairs of accelerometers extended over a region of space can be used to detect differences (gradients) in the proper accelerations of frames of references associated with those points. These devices are called gravity gradiometers, as they measure gradients in the gravitational field. Such pairs of accelerometers in theory may also be able to detect gravitational waves.

The purpose of the accelerometer :

Accelerometers in phones

The application of accelerometers extends to multiple disciplines, both academic and consumer-driven. For example, accelerometers in laptops protect hard drives from damage. If the laptop were to suddenly drop while in use, the accelerometer would detect the sudden free fall and immediately turn off the hard drive to avoid hitting the reading heads into the hard drive platter. Without this, the two would strike and cause scratches to the platter for extensive file and reading damage. Accelerometers are likewise used in cars as the industry method way of detecting car crashes and deploying airbags almost instantaneously.

In another example, a dynamic accelerometer measures gravitational pull to determine the angle at which a device is tilted with respect to the Earth. By sensing the amount of acceleration, users analyze how the device is moving.

Accelerometers allow the user to understand the surroundings of an item better. With this small device, you can determine if an object is moving uphill, whether it will fall over if it tilts any more, or whether it’s flying horizontally or angling downward. For example, smartphones rotate their display between portrait and landscape mode depending on how you tilt the phone.

How do accelerometers work?

There are many different ways to make an accelerometer! Some accelerometers use the piezoelectric effect - they contain microscopic crystal structures that get stressed by accelerative forces, which causes a voltage to be generated. Another way to do it is by sensing changes in capacitance. If you have two microstructures next to each other, they have a certain capacitance between them. If an accelerative force moves one of the structures, then the capacitance will change. Add some circuitry to convert from capacitance to voltage, and you will get an accelerometer. There are even more methods, including use of the piezoresistive effect, hot air bubbles, and light.

Transistors

Any discussion of semiconductor devices isnt complete without mentioning the "Transistors". The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems.

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

Importance

The transistor is the key active component in practically all modern electronics. Many consider it to be one of the greatest inventions of the 20th century. Its importance in today's society rests on its ability to be mass-produced using a highly automated process (semiconductor device fabrication) that achieves astonishingly low per-transistor costs. The invention of the first transistor at Bell Labs was named an IEEE Milestone in 2009.

Although several companies each produce over a billion individually packaged (known as discrete) transistors every year, the vast majority of transistors are now produced in integrated circuits (often shortened to IC,microchips or simply chips), along with diodes, resistors, capacitors and other electronic components, to produce complete electronic circuits. A logic gate consists of up to about twenty transistors whereas an advanced microprocessor, as of 2009, can use as many as 3 billion transistors (MOSFETs)

Transistors are manufactured in different shapes but they have three leads (legs). 
The BASE - which is the lead responsible for activating the transistor.
The COLLECTOR - which is the positive lead.
The EMITTER - which is the negative lead.
The diagram below shows the symbol of an NPN transistor. They are not always set out as shown in the diagrams to the left and right, although the ‘tab’ on the type shown to the left is usually next to the ‘emitter’.

Working: The design of a transistor allows it to function as an amplifier or a switch. This is accomplished by using a small amount of electricity to control a gate on a much larger supply of electricity, much like turning a valve to control a supply of water. Transistors are composed of three parts – a base, a collector, and an emitter. The base is the gate controller device for the larger electrical supply. The collector is the larger electrical supply, and the emitter is the outlet for that supply. By sending varying levels of current from the base, the amount of current flowing through the gate from the collector may be regulated. In this way, a very small amount of current may be used to control a large amount of current, as in an amplifier. The same process is used to create the binary code for the digital processors but in this case a voltage threshold of five volts is needed to open the collector gate. In this way, the transistor is being used as a switch with a binary function: five volts – ON, less than five volts – OFF.  Types of transistors : 1. JUNCTION TRANSISTORS  A junction transistor consists of a thin piece of one type of semiconductor material between two thicker layers of the opposite type. For example, if the middle layer is p-type, the outside layers must be n-type. Such a transistor is an NPN transistor. One of the outside layers is called the emitter, and the other is known as the collector. The middle layer is the base. The places where the emitter joins the base and the base joins the collector are called junctions.  The layers of an NPN transistor must have the proper voltage connected across them. The voltage of the base must be more positive than that of the emitter. The voltage of the collector, in turn, must be more positive than that of the base. The voltages are supplied by a battery or some other source of direct current. The emitter supplies electrons. The base pulls these electrons from the emitter because it has a more positive voltage than does the emitter. This movement of electrons creates a flow of electricity through the transistor.  The current passes from the emitter to the collector through the base. Changes in the voltage connected to the base modify the flow of the current by changing the number of electrons in the base. In this way, small changes in the base voltage can cause large changes in the current flowing out of the collector.  2. FIELD EFFECT TRANSISTORS  A field effect transistor has only two layers of semiconductor material, one on top of the other. Electricity flows through one of the layers, called the channel. A voltage connected to the other layer, called the gate, interferes with the current flowing in the channel. Thus, the voltage connected to the gate controls the strength of the current in the channel. There are two basic varieties of field effect transistors-the junction field effect transistor(JFET) and the metal oxide semiconductor field effect transistor (MOSFET). Most of the transistors contained in today's integrated circuits are MOSFETS's.

Light Emitting Diodes

What is a LED ?

A light-emitting diode (LED) is a two-lead semiconductor light source. It resembles a basic pn-junction diode, which emits light when activated. When a fitting voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor.

A LED

LEDs are so common, they come in dozens of different shapes and sizes. The LEDs you are most likely to use are the through hole LEDs with two legs. There are lots of LEDs that are small and hard to solder but these are easy to use with a breadboard because they have long wires we can stick in. The clear or clear-ish bulb is what protects the light emitter (thats where the magic happens). In fact, the first two letters of LED stand for Light Emitting.

A really nice thing about LEDs is that they are very simple. Unlike some chips that have dozens of pins with names and special uses, LEDs have only two wires. One wire is the anode (positive) and another is the cathode (negative). The two wires have different names because LEDs only work in one direction and we need to keep track of which pin is which. One goes to the positive voltage and the other goes to the negative voltage. Electronic parts that only work in 'one direction' like this are called Diodes, thats what the last letter of LED stands for.

• The longer lead goes to the more-positive voltage
• Current goes in one direction, from the anode (positive) to the cathode(negative)
• LEDs that are 'backwards' won't work - but they won't break either

It's all a little confusing - we often have to think about which is which. So to make it easy, there's only one thing you need to remember and that's the LED wont light up if you put it in backwards. If you're ever having LED problems where they are not lighting, just flip it around. Its very hard to damage an LED by putting it in backwards so don't be scared if you do.

What are LEDs used for?

LEDs are mostly used for two things: illumination and indication. These are technical words but are good to understand because if you want an LED for one thing and you buy the wrong thing you'll be pretty bummed.

Headlights should be bright!

Illumination means to "shine light onto something" - like a flashlight or headlights. You want your headlights to be bright as heck.

Brake lights should be bright enough to see, but don't need to light up the road!

Indication mean to "point something out" - like a turn signal or brake lights on a car. You don't want your car's turn signal to blind people!

If you get the wrong type you could end up with a DIY flashlight that is dim, or a control panel that burns people's eyes!

Diffused LEDs are really good at indication, they look soft and uniform and you can see them well from any angle.

Clear LEDs are really good at illumination, the light is direct and powerful - but you can't see them well from an angle because the light is only going forward.

How Can a Diode Produce Light?

Light is a form of energy that can be released by an atom. It is made up of many small particle-like packets that have energy and momentum but no mass. These particles, called photons, are the most basic units of light.

Photons are released as a result of moving electrons. In an atom, electrons move in orbitals around the nucleus. Electrons in different orbitals have different amounts of energy. Generally speaking, electrons with greater energy move in orbitals farther away from the nucleus.

For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level. Conversely, an electron releases energy when it drops from a higher orbital to a lower one. This energy is released in the form of a photon. A greater energy drop releases a higher-energy photon, which is characterized by a higher frequency. 

As we saw in the last section, free electrons moving across a diode can fall into empty holes from the P-type layer. This involves a drop from the conduction band to a lower orbital, so the electrons release energy in the form of photons. This happens in any diode, but you can only see the photons when the diode is composed of certain material. The atoms in a standard silicon diode, for example, are arranged in such a way that the electron drops a relatively short distance. As a result, the photon's frequency is so low that it is invisible to the human eye -- it is in the infrared portion of the light spectrum. This isn't necessarily a bad thing, of course: Infrared LEDs are ideal for remote controls, among other things.

Visible light-emitting diodes (VLEDs), such as the ones that light up numbers in a digital clock, are made of materials characterized by a wider gap between the conduction band and the lower orbitals. The size of the gap determines the frequency of the photon -- in other words, it determines the color of the light. While LEDs are used in everything from remote controls to the digital displays on electronics, visible LEDs are growing in popularity and use thanks to their long lifetimes and miniature size. Depending on the materials used in LEDs, they can be built to shine in infrared, ultraviolet, and all the colors of the visible spectrum in between.

LM 358

In today's post we will talk about the IC LM358. The LM358 IC is commonly used in making IR sensor modules and is one of its major component.

Description:

Pin configuration of LM358

The LM358 contains two independent high gain operational amplifiers with internal frequency compensation. The two op- amps operate over a wide voltage range from a single pow- er supply. Also use a split power supply. The device has low power supply current drain, regardless of the power supply voltage. The low power drain also makes the LM358 a good choice for battery operation.

When your project calls for a traditional op-amp function, now you can streamline your design with a simple single power supply. Use ordinary +5VDC common to practice any digital system or personal computer application, without requiring an extra 15V power supply just to have the interface electronics you need.

The LM358 is a versatile, rugged workhorse with a thousand- and-one uses, from amplifying signals from a variety of transducers to DC gain blocks, or any op-amp function. 

LM358 can be used to construct a stable amplifier, an inverting amplifier and a non-inverting one since there are two op amps on each LM358 chip. The herein picture shows the pinout schematic diagram of the LM358.

Features :
Internally frequency compensated for unity gain
Large DC voltage gain: 100dB
Wide bandwidth (unity gain): 1 MHz (temperature-compensated)
Wide power supply range: 
 Single supply:3VDC to 32 VDC
 Dual supplies:+1.5VDC to +16VDC
Input common-mode voltage range includes ground
Large output voltage swing: 0V DC to VCC-1.5V DC
Power drain suitable for battery operation
Low input offset voltage and offset current

Differential input voltage range equal to the power supply voltage

In earlier posts we discussed about the motors , the H bridge but the most important component in the working of motors is the IC called the L293D motor IC.

L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as current amplifiers since they take a low-current control signal and provide a higher-current signal. This higher current signal is used to drive the motors.

L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors can be driven simultaneously, both in forward and reverse direction. The motor operations of two motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise and anticlockwise directions, respectively.

The L293D IC

Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to start operating. When an enable input is high, the associated driver gets enabled. As a result, the outputs become active and work in phase with their inputs. Similarly, when the enable input is low, that driver is disabled, and their outputs are off and in the high-impedance state.

Working of L293D

The there 4 input pins for this l293d, pin 2,7 on the left and pin 15 ,10 on the right as shown on the pin diagram. Left input pins will regulate the rotation of motor connected across left side and right input for motor on the right hand side. The motors are rotated on the basis of the inputs provided across the input pins as LOGIC 0 or LOGIC 1.

In simple you need to provide Logic 0 or 1 across the input pins for rotating the motor.

L293D Logic Table.

Lets consider a Motor connected on left side output pins (pin 3,6). For rotating the motor in clockwise direction the input pins has to be provided with Logic 1 and Logic 0.   

Motor control through L293D IC

• Pin 2 = Logic 1 and Pin 7 = Logic 0 | Clockwise Direction
• Pin 2 = Logic 0 and Pin 7 = Logic 1 | Anticlockwise Direction
• Pin 2 = Logic 0 and Pin 7 = Logic 0 | Idle [No rotation] [Hi-Impedance state]
• Pin 2 = Logic 1 and Pin 7 = Logic 1 | Idle [No rotation]

In a very similar way the motor can also operated across input pin 15,10 for motor on the right hand side.