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.

The basics of working of a simple robot

We learnt about the different types of robots , their uses and their possible disadvantages as well. Now the important thing is what are the important components of a robot?

As this blog is made for tutorial purposes ,  we will start from the basics and tell you about the components a most basic robot should have.


To start with , let us consider these points :-

A. To work a robot needs an electronic brain which decides what to do and when to do ? for this purpose a robot has a microcontroller. The microcontrollers availaible are of different type and memory sizes. In our tutorials we will be using AVR microcontrollers namely Atmega8/16/32.

B. To get the data from the nearby surrounding , the robot needs to sense them first. Similar to the sensing ability our body has , after the microcontroller the sensors are the most important component.
A robot can have several type of sensors : IR sensors , ultrasonic sensors , thermal sensors , light sensors etc.

C. After the data recieved from the sensors have been processed an output component is required so as the robot does the desired output functions.For this purposes we connect motors etc with the robot. The motors available are of different types namely stepper motor , geared motor , servo motors etc. In case of robots like mechanical hand the output is achieved by use of actuators ( a type of motor itself ).

D. The power source . No doubt if your robot has high grade above mentioned components but the robot is completely useless if it doesnt have a power source.


 Now we will discuss a bit in detail about the several components used :

• Microcontroller :-

A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in PCs or other general purpose applications.

Block diagram of Microcontroller

Even though there is a large number of different types of microcontrollers and even more programs created for their use only, all of them have many things in common. Thus, if you learn to handle one of them you will be able to handle them all. A typical scenario on the basis of which it all functions is as follows:

1. Power supply is turned off and everything is still…the program is loaded into the microcontroller, nothing indicates what is about to come…
2. Power supply is turned on and everything starts to happen at high speed! The control logic unit keeps everything under control. It disables all other circuits except quartz crystal to operate. While the preparations are in progress, the first milliseconds go by.
3. Power supply voltage reaches its maximum and oscillator frequency becomes stable. SFRs are being filled with bits reflecting the state of all circuits within the microcontroller. All pins are configured as inputs. The overall electronis starts operation in rhythm with pulse sequence. From now on the time is measured in micro and nanoseconds.
4. Program Counter is set to zero. Instruction from that address is sent to instruction decoder which recognizes it, after which it is executed with immediate effect.
5. The value of the Program Counter is incremented by 1 and the whole process is repeated...several million times per second.

• Sensors :

A sensor is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. For example, a mercury in glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A  thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards.

The different type of sensors availaible to us are: 

1. IR sensors ( Infrared sensors)

2. Thermal sensors

3.Proximity sensors

4. Light sensors

5. Moisture sensors

6. smoke sensors
7. ultrasonic sensors etc.

For the beginner purposes , we will talk only about the IR sensors.

Working Principle

Working of an IR sensor

A typical system for detecting infrared radiation using infrared sensors includes the infrared source such as blackbody radiators, tungsten lamps, and silicon carbide. In case of active IR sensors, the sources are infrared lasers and LEDs of specific IR wavelengths. Next is the transmission medium used for infrared transmission, which includes vacuum, the atmosphere, and optical fibers.

Thirdly, optical components such as optical lenses made from quartz, CaF₂, Ge and Si, polyethylene Fresnel lenses, and Al or Au mirrors, are used to converge or focus infrared radiation. Likewise, to limit spectral response, band-pass filters are ideal.

Finally, the infrared detector completes the system for detecting infrared radiation. The output from the detector is usually very small, and hence pre-amplifiers coupled with circuitry are added to further process the received signals.

• Motors :-

A motor is an electric machine that converts electrical energy into mechanical energy.In robotics several type of motors are used for various purposes.For instance the geared motor is what we commonly use for robot's locomotion.

The 3 main types of motors that are commonly used for robotic purposes are :-

DC geated motor

1. DC geared motors :- Geared DC motors can be defined as an extension of DC motor which already had its . A geared DC Motor has a gear assembly attached to the motor. The speed of motor is counted in terms of rotations of the shaft per minute and is termed as RPM .The gear assembly helps in increasing the torque and reducing the speed. Using the correct combination of gears in a gear motor, its speed can be reduced to any desirable figure. This concept where gears reduce the speed of the vehicle but increase its torque is known as gear reduction.  This Insight will explore all the minor and major details that make the gear head and hence the working of geared DC motor.

2. Stepper motor :- 

A stepper motor  is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can then be commanded to move and hold at one of these steps without any feedback sensor (an open loop controller), as long as the motor is carefully sized to the application. DC brushed motors rotate continuously when voltage is applied to their terminals.

Stepper motor

The stepper motor is known by its important property to convert a train of input pulses (typically square wave pulses) into a precisely defined increment in the shaft position. Each pulse moves the shaft through a fixed angle. Stepper motors effectively have multiple "toothed" electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller. To make the motor shaft turn, first, one electromagnet is given power, which magnetically attracts the gear's teeth. When the gear's teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those rotations is called a "step", with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle.

Servo motor

3. Servomotor : A servomotor is a rotor actuator that allows for precise control of angular position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors.

Servomotors are not a specific class of motor although the term servomotor is often used to refer to a motor suitable for use in a closed-loop control system.

In our next post we will be discussing in detail about the microcontrollers , their types and their architectures.


Comments and views will be appreciated.