Powering your Rasberry Pi

I bought a Rasberry Pi recently and quickly the question I was faced with was: How to power it? Then I started digging into some specifics of power supplies. Most common answer was to use a standard micro-USB phone charger which ships with most Android phones. While this worked for me, I was curious to know more about power supplies.

Let us think about what a power supply is really. The electricity that runs in our wall sockets, is AC or alternating current. This AC supply has to be converted into a low voltage DC supply before powering your electronic circuits. This is the primary function of a power supply.

Standard power consumption of the Raspberry Pi device is

• Board A: 5V, 500 mA (2.5W) without any devices connected (e.g. USB, Ethernet, HDMI)
• Board B: 5V, 700 mA (3.5W) without any devices connected (e.g. USB, Ethernet, HDMI)

But it doesn’t end on that. We need to ensure that the power supply we use can provide enough electric current to power the Pi plus any additional peripherals. In addition, we need to take into account inefficiencies of the supply itself and the cable between the power supply and Raspberry Pi. Most of us will use the USB ports to connect a keyboard, mouse or a Bluetooth module. The community advises that we use a power supply that can at least supply 1A of current. A poor quality power supply unit may result in corruption of your SD card. The Pi gets unstable, freezes, lags for even simple tasks if enough power is not supplied. So if you have such problems, better take a look at the power ratings of your supply.

The power required by the Pi varies depending on what peripherals are connected and what functions it is currently performing. The Pi draws extra power when:

• Running a GUI.
• Connecting USB devices and an Ethernet connection.
• When running the GPU.

This means that it is difficult to say exactly how much power is needed at any time. Adding peripherals increases the loading on the power supply to your board and this, in turn, may affect the voltage presented to the Raspberry Pi. If the Raspberry Pi's supply voltage falls below a certain value (around 4.75 V), or it begins to fluctuate, your setup may become unstable.

For regular "low power" USB devices this doesn't cause a problem as they are designed to work with voltages as low as 4.4 Volt. This isn't the case however with some USB devices such as WiFi dongles which may need 4.75 Volt, and are also known to draw more than 150 mA when configured and active. Each of the two USB ports on the Pi has a polyfuse rated at 140 mA, so any connected USB devices should draw less than this amount of current. The polyfuse itself can cause significant voltage drop. So be sure you know what you connect to the Pi. It is common to use a powered USB hub to power your USB peripherals. Also know that you can power your Pi from the USB hub also. There is a thread on that too.

Alternate ways to power your Pi: 
Although I never tried, but there are some interesting alternate ways to power your Pi. They are listed here.

There is still a _lot_ to know about power supplies and how they affect parts of an electronic and electrical devices. For example, how does overclocking affect power requirements? It is an interesting topic and I will keep this post updated on any new things that I learn and may be useful to others.

All the info written above has been compiled by reading blogs, wiki, manuals, etc. If you feel there is anything incorrect/overlooked, I would be more than glad to correct them.

Using Raspberry Pi as IRC Client

I wanted to be continually logged into IRC and also use it as a logging client for message on the #doothings IRC channel.

What better way than to use Raspberry Pi?

Steps for using Raspberry Pi as IRC Client

1. We will use IRSSI, whici is a terminal based IRC client.
2. Install it by running sudo apt-get install irssi
3. Also install screen by running sudo apt-get install screen
4. screen and then press Enter
5. IRSSI irssi
6. /server irc.freenode.net
7. /join #doothings
8. Now you have logged-in to the #doothings IRC Channel.
9. To Detach from the Client. Press Ctrl + a and then d
10. You should be back to the terminal window.
11. To rejoin the IRC window run screen -r

Settings for irssi

1. To ignore joins / quits / nicks changes on a specific channel.
   /ignore -channels #chan1,#chan2,#chan3 * JOINS PARTS QUITS NICKS
2. Auto Connect to a Server on startup
   /SERVER ADD -auto -network IRCnet irc.freenode.net 6667
3. Auto Join to Specificed channels
   /CHANNEL ADD -auto #doothings IRCnet
4. To Keep logging all these conversations
   /SET AUTOLOG ON
5. To set Nicks and Real Name etc.
   /SET -> This should show all existing configured parameters.
   To change these just say
   /SET param-name value like /SET nick nism-pi
6. /SAVE to save the entire configuration.
   All these steps if you think need to be improved, you can send in a pull request here https://github.com/iot-pune/raspberrypi/blob/master/IRC-client.md

Arduino with real time web application using web sockets

Purpose of this experiment is to demonstrate real time aspect of the web to pull data from an Arduino.

Arduino can be clubbed together with several sensor to receive data of surroundings and do anything with data. Once you have data with you, imagination is the limit like sending surrounding temperature to Twitter as tweet, check mail when you come close to your computer, turn off volume when an ad comes on TV etc. 

Following POC shows use of Arduino with LDR sensor to plot real time graph of Light around you.

You will need following things for our project : 

1. Arduino UNO or Freeduino 
2. LDR or photo-resistor 
3. 10k ohm resistor (Voltage divider)
4. Computer 

LDR is basically a simple light sensor that changes the resistance with light. We will measure amount of voltage is on LDR using analog read of Arduino. With Arduino analog read, 5v is highest value read as 1023 and 0v is lowest value read as 0.

Let connect things 

Connect your LDR and resistor as shown in figure., 

Now coding part,

The idea here is to read sensor reading using Arduino and send them to computer for further processing, so we will read sensor data and send it serial port of computer where Arduino is connected. 

filename: LDR.ino

int LDR = 0;

void setup(){

  Serial.begin(9600);

}

void loop(){ 

  int Reading = analogRead(LDR);

  Serial.println(Reading);

  delay(250);

}

Code is pretty self-explanatory. Now the web part here we will use websocket for reading values and plotting real time graph out of read values. We will not discuss websocket and its implementation as this is out of scope of this project (which itself is big topic for discussion).

In order to run the code you need to install Python with following modules 

1. geventwebsocket.handler 
2. gevent 
3. serial 

Python provides module called 'serial' which enables to read and write to serial port of computer.
Here websocket server written in Python, 

filename: LDRreader.py 

from geventwebsocket.handler import WebSocketHandler

from gevent import pywsgi

import gevent

import serial

# PORT used for websocket client

PORT = 8090

import os

import random

def handle(ws):

    """  This is the websocket handler function.  Note that we

    can dispatch based on path in here, too."""

    serial_read = serial.Serial('COM31', 9600)

    if ws.path == '/data':

        for i in xrange(10000):

            signal = serial_read.readline()

            ws.send("0 %s %s\n" % (i, signal))

            print "0 %s %s\n" % (i, signal)

            gevent.sleep(0.1)

def app(environ, start_response):

    if environ['PATH_INFO'] == '/test':

        start_response("200 OK", [('Content-Type', 'text/plain')])

        return ["blah blah"]

    elif environ['PATH_INFO'] in ("/data"):

        handle(environ['wsgi.websocket'])

    else:

        start_response("404 Not Found", [])

        return []

def main():

print "In main, Starting WSGIServer"

server = pywsgi.WSGIServer(('0.0.0.0', PORT), app,

handler_class=WebSocketHandler)

try:

server.serve_forever() 

except:

pass

if __name__ == "__main__":

main()

Now websocket client which will actual receive data and plot it on web browser, you need this library for plotting graph. Download and keep in same directory where LDR.html is present. 

filename: LDR.html

<!DOCTYPE html>

<html>

<head>

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>

<script src="jquery.flot.js"></script>

<script>

var iets = "";

window.onload = function() {

    var data = {};

try {

var s = new WebSocket("ws://localhost:8090/data");

}

catch (e) {

var s = new MozWebSocket("ws://localhost:8090/data");

}

    s.onopen = function() {

        console.log('Websocket Open');

        s.send('hi');

    };

    s.onmessage = function(e) {

      console.log('got ' + e.data);

      var lines = e.data.split('\n');

      for (var i = 0; i < lines.length - 1; i++) {

        var parts = lines[i].split(' ');

        var d = parts[0], x = parseFloat(parts[1]), y = parseFloat(parts[2]);

        if (!(d in data)) data[d] = [];

        data[d].push([x,y]);

      }

      var plots = [];

      for (var d in data) plots.push( { data: data[d].slice(data[d].length - 200) } );

      $.plot( $("#holder"), plots,

              {

                series: {

                  lines: { show: true, fill: true },

                },

                yaxis: { min: 0 },

              } );

      s.send('');

    };

};

</script>

</head>

<body>

<h3>LDR Plot</h3>

<div id="holder" style="width:800px;height:350px"></div>

</body>

</html>

Now start our websocket server using 

# python LDRreader.py  

now go to browser and type http://localhost:8090 and bam !!! 

You will see plotting graph.

Getting started with the BeagleBone Black

Arduino is the most ubiquitous development platform, period. Anyone who has entered the world of DIY electronics most probably started off with an Arduino. The reasons for this are it's ease, the enormous amount of documentation in the form of wikis, code samples, video tutorials, etc.
But there comes a point when the Arduino just isn't enough for your needs. You need more muscle.

Enter BeagleBone Black.
A 1Ghz, 512MB RAM "mini-computer" with 2 GB of onboard memory.
At $45, its in the competitive price range of the RaspberryPi (35$), pcDuino(59$), etc.

It comes from one of the oldest players in the Embedded Linux worlds, Beagleboard.org. It's their 4th ARM dev board, and the 1st in this price range (previous boards were Beagleboard, Beageboard xM and the Beaglebone white).

Pros as compared to the Pi:
Since the Pi has gained a lot of popularity, it's easier to compare it with that.

• More processing power(1Ghz as compared to 700Mhz)
• No need for SD card( has 2 GB of onboard flash, which is more than enough to run your fav Linux distro. Of course it has uSD card slot, just in case you think you need more space)
• No need for external power supply( directly plugs in to your laptop/PC and runs like the Arduino)
• Has a LOT more interfaces as compared to the Pi( more GPIOs. Has onboard PWM, ADC too unlike the Pi)
  Full list here http://circuitco.com/support/index.php?title=BeagleBoneBlack
• Has many many capes available.
  http://circuitco.com/support/index.php?title=BeagleBone_Capes
  Capes are analogous to shields for Arduino.
  It's not always possible to give all kinds of interfaces on the board. So based on your project needs, you can use one of the available capes to add even more functionality.
  
  You can of course find a lot more comparisons if you ask Google ;) 

Getting started:

Since the BBB rocks Linux on board, you don't really have any restriction on the kind of programming language you choose. 

Any kind of input/output is done by using 

Links to get started:

1. SRM (System Reference Manual. Read through this once to get familiar with all the features and interfaces.)
2. Wiki
3. Mailing list (this should be your first stop for any issues once you get your Black. It's very active and very helpful. Remember to search previous posts before posting your doubt, someone might have had the same doubt)
4. IRC - #beagle on Freenode
5. Derek Molloy's blogs ( has some really cool tutorials, videos, etc to get started)
6. Userspace Arduino project

Get it:

Some of the Indian shops which will ship you a Black are

1. http://tenettech.com/product/2912/beaglebone-blackhttp://tenettech.com/product/2912/beaglebone-black
2. http://shop.sumeetinstruments.com/index.php?route=product/product&keyword=beaglebone+black&category_id=0&product_id=965
3. http://www.crazypi.com/index.php?route=product/product&product_id=79&search=beagle
   
   Note: these guys don't really have permanent links to their products. So if above links don't work, try searching for them from the Homepage.

DigiKey, Adafruit, element14, etc are the official distributors for the BBB. More info about them here http://beagleboard.org/Products

Open Source Home Automation Project using Arduino UNO + Ethernet Shield

This is Open Source Home Automation Project based on Arduino Uno and Arduino Wiznet based Ethernet shield.

How Does it Work

The main brain for this project is Arduino UNO Board along with Arduino Ethernet Shield to give it a wireless connectivity.Arduino runs a code to control a Relay board according to the input and also serves a web page through which respective output to the relay board can be controlled.Through relay controller board we can control lamps, tubes or any AC power sockets.

You will be able to control all of your AC Appliances wirelessly with the help of any WIFI Enabled device.

STEP 1:

Relay Controller Board Build Tutorial:

Quantity of the components depends upon how many channels you want e.g. if you want to control more than one light then you will have to add that much number of relays on your controller board.

Here is the material list which will be needed to build the board: (Quantity of the components given for making 1 channel relay controller)

Sr.No	Component Names	Quantity
1	Relay (I have used GOODSKY RWH-SH-105D Relay)	1
2	Transistor 2N3904	1
3	1K Resistor	2
4	10K Resistor	1
5	1N4148 Diode	1
6	Red Led 3mm	1
7	3 Pin PCB Mount Connector	1
8	1 Pin PCB Mount Connector	1

Above components are for making of single controller board you can multiply number of the components depending on how many relay controller you want.

Here in the circuit diagram Pin no.2 will be connected to the arduino control output pin and other two will be connected to +5V and Gnd accordingly.

After soldering all of your components according to the above circuit diagram the board should look like this.

Front View

Rear View

This is single relay controller board. You can extend this to as many as you want. I have made 5 channel relay controller board as below.

Note:

All the usual warnings apply: Mains voltage (120VAC or 220VAC) can kill you. This project, if done incorrectly, could certainly burn down your house. Do not work on or solder to any part of a project while it is plugged into the wall socket - just unplug it before modifying anything!

STEP 2:

Getting IP Address Of Arduino Ethernet Shield:

 Mount your Arduino Ethernet shield on Arduino Uno as shown:

Now connect your Uno Board to PC with USB cable and open Arduino IDE. After Opening up you will find blank Arduino window. Now go to File--> Example --> Ethernet --> dhcp address printer sketch. Your Ethernet shields MAC address is printed on back of it as follow you will need this in DHCP ADDRESS PRINTER code to get the IP address of your Ethernet shield.

In DHCP address printer sketch put your MAC address as given on back of the Ethernet shield and upload it to the Arduino board.

After finished uploading connect Arduino Ethernet shield to internet with Ethernet cable once connected then open up you serial monitor of Arduino IDE the IP address allotted to your Ethernet shield will be displayed e.g. (xxx.xxx.x.xxx) note it down somewhere because you are going to need this in further codes.

STEP 3:

BuildingMainCircuitConnection :

Now we are ready with our Relay controller board. So, it’s time to move on to the Main Circuit Connections. Here I have given the pin configuration for the whole Autohome Project.

Arduino Digital Pin No.	Pin Usage
4	will be used for Infrared Receiver
5	used as Output Pins to control Relays
6	used as Output Pins to control Relays
7	used as Output Pins to control Relays
8	used as Output Pins to control Relays
9	used as Output Pins to control Relays
10	will be used by Arduino Ethernet Shield
11	will be used by Arduino Ethernet Shield
12	will be used by Arduino Ethernet Shield
13	will be used by Arduino Ethernet Shield

Note: For relays it is recommended to power it from separate source not from Arduino (I have powered it from Arduino only but since here we are working with single board. As board number increases Arduino won’t be able to supply sufficient power to the boards.)

Here is the connection diagram:

In this way you can do necessary soldering work to make following connection.

You can also make your own protoshield which can easily fit on top Arduino like this:

Once you finish soldering stuff, now you are ready for your main code upload.

STEP 4:

Uploading Arduino AutoHome code to the Board:

Here is the Arduino AutoHome code just copy and paste it into your Arduino IDE sketch.

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//for use with IDE 1.0 //open serial monitor to see what the arduino receives //use the \ slash to escape the " in the html //for use with W5100 based ethernet shields // this project is hosted at // http://code.google.com/p/arduino-autohome/ #include <SPI.h> #include <Ethernet.h> byte mac[] = { 0x90, 0xA2, 0xDA, 0x0D, 0x78, 0xE0 }; // <------- PUT YOUR MAC Address Here byte ip[] = { 192, 168, 1, 102 }; // <------- PUT YOUR IP Address Here byte gateway[] = { 192, 168, 1, 254 }; // <------- PUT YOUR ROUTERS IP Address to which your shield is connected Here byte subnet[] = { 255, 255, 255, 0 }; // <------- It will be as it is in most of the cases EthernetServer server(80); // <------- It's Defaulf Server Port for Ethernet Shield String readString; ////////////////////// void setup() {   pinMode(6, OUTPUT); // Pin Assignment through which relay will be controlled   pinMode(7, OUTPUT);   pinMode(8, OUTPUT);   pinMode(9, OUTPUT);         //start Ethernet      Ethernet.begin(mac, ip, gateway, subnet);   server.begin();      //enable serial data print      Serial.begin(9600);   Serial.println("server LED test 1.0"); // so that we can know what is getting loaded } void loop() {          // Create a client connection   EthernetClient client = server.available();   if (client) {     while (client.connected()) {       if (client.available()) {         char c = client.read();                  //read char by char HTTP request         if (readString.length() < 100) {           //store characters to string           readString += c;           //Serial.print(c);         }         //if HTTP request has ended         if (c == '\n') {           ///////////////           Serial.println(readString); //print to serial monitor for debuging           /* Start OF HTML Section. Here Keep everything as it is unless you understands its working */                      client.println("HTTP/1.1 200 OK"); //send new page           client.println("Content-Type: text/html");           client.println();           //client.println("<meta http-equiv=\"refresh\" content=\"5\">");           client.println("<HTML>");           client.println("<HEAD>");           client.println("<meta name='apple-mobile-web-app-capable' content='yes' />");           client.println("<meta name='apple-mobile-web-app-status-bar-style' content='black-translucent' />");           client.println("<link rel=\"stylesheet\" type=\"text/css\" href=\"http://arduino-autohome.googlecode.com/svn/trunk/autohome.css\" />");                                 client.println("</HEAD>");           client.println("<body bgcolor=\"#D0D0D0\">");                      client.println("<hr/>");           client.println("<hr/>");           client.println("<h4><center><img border=\"2\" src=\"https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7D936U9HueV3OmYSI_yfSMGiFYI9L5gDeW2ydPt9eTugpNaUxyr_ABI4QjhPSRt3bhA4v_eLg3GYq133qd9QDqu5v7x9OwdsDSfQZyy2fc9bWrEneR1WpAN7LWgdTfMOpehMpzShvW7U/s960/Logo.jpg\" /></center></h4>");           client.println("<hr/>");           client.println("<hr/>");                      client.println("<br />");           client.println("<br />");           client.println("<br />");           client.println("<br />");           client.println("<br />");                    // Relay Control Code           client.println("<a href=\"/?relay1on\"\">Turn On Light 1</a>");           client.println("<a href=\"/?relay1off\"\">Turn Off Light 1</a><br />");                      client.println("<br />");           client.println("<br />");           client.println("<br />");           client.println("<br />");                      client.println("<a href=\"/?relay2on\"\">Turn On Light 2</a>");           client.println("<a href=\"/?relay2off\"\">Turn Off Light 2</a><br />");                      client.println("<br />");           client.println("<br />");           client.println("<br />");           client.println("<br />");                      client.println("<a href=\"/?relay3on\"\">Turn On Light 3</a>");           client.println("<a href=\"/?relay3off\"\">Turn Off Light 3</a><br />");                      client.println("<br />");           client.println("<br />");           client.println("<br />");           client.println("<br />");                      client.println("<a href=\"/?relay4on\"\">Turn On Light 4</a>");           client.println("<a href=\"/?relay4off\"\">Turn Off Light 4</a><br />");           client.println("<br />");           client.println("<br />");                                                        // control arduino pin via ethernet Start //                                 if(readString.indexOf("?relay1on") >0)//checks for on           {             digitalWrite(6, HIGH); // set pin 4 high             Serial.println("Led On");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/on.png' />");             //client.println("Light 1 Is On");             client.println("<br />");         }           else{           if(readString.indexOf("?relay1off") >0)//checks for off           {             digitalWrite(6, LOW); // set pin 4 low             Serial.println("Led Off");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/off.png' />");             //client.println("Light 1 Is Off");             client.println("<br />");         }           }                      if(readString.indexOf("?relay2on") >0)//checks for on           {             digitalWrite(7, HIGH); // set pin 4 high             Serial.println("Led On");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/on.png' />");             //client.println("Light 2 Is On");             client.println("<br />");           }           else{           if(readString.indexOf("?relay2off") >0)//checks for off           {             digitalWrite(7, LOW); // set pin 4 low             Serial.println("Led Off");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/off.png' />");             //client.println("Light 2 Is Off");             client.println("<br />");           }           }                       if(readString.indexOf("?relay3on") >0)//checks for on           {             digitalWrite(8, HIGH); // set pin 4 high             Serial.println("Led On");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/on.png' />");            // client.println("Light 3 Is On");             client.println("<br />");           }           else{           if(readString.indexOf("?relay3off") >0)//checks for off           {             digitalWrite(8, LOW); // set pin 4 low             Serial.println("Led Off");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/off.png' />");             //client.println("Light 3 Is Off");             client.println("<br />");           }           }                                  if(readString.indexOf("?relay4on") >0)//checks for on           {             digitalWrite(9, HIGH); // set pin 4 high             Serial.println("Led On");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/on.png' />");             //client.println("Light 4 Is On");             client.println("<br />");           }           else{           if(readString.indexOf("?relay4off") >0)//checks for off           {             digitalWrite(9, LOW); // set pin 4 low             Serial.println("Led Off");             client.println("<link rel='apple-touch-icon' href='http://chriscosma.co.cc/off.png' />");             //client.println("Light 4 Is Off");             client.println("<br />");           }           }                     // control arduino pin via ethernet End //                                         // Relay Status Display           client.println("<center>");           client.println("<table border=\"5\">");           client.println("<tr>");                      if (digitalRead(6))           {            client.print("<td>Light 1 is ON</td>");                       }           else           {             client.print("<td>Light 1 is OFF</td>");                       }                                 client.println("<br />");                      if (digitalRead(7))           {            client.print("<td>Light 2 is ON</td>");                       }           else           {             client.print("<td>Light 2 is OFF</td>");                        }                      client.println("</tr>");           client.println("<tr>");                      if (digitalRead(8))           {            client.print("<td>Light 3 is ON</td>");                       }           else           {             client.print("<td>Light 3 is OFF</td>");                        }                                                   if (digitalRead(9))           {            client.print("<td>Light 4 is ON</td>");                      }           else           {             client.print("<td>Light 4 is OFF</td>");                       }                      client.println("</tr>");           client.println("</table>");                      client.println("</center>");                                            //clearing string for next read                      readString="";           client.println("</body>");           client.println("</HTML>");           delay(1);           //stopping client           client.stop();         }       }     }   } }

Upload this code to your UNO board. Now you are ready to your your Automation Project, just plug your Ethernet shield to router and and you will be able to find the control page on the IP Address specified by in in the Arduino Code. So directly enter the  IP address in the web browser of the the device which is on the same network as that of your Arduino.

So you will have the control page as shown below:

As you understand the code you can modify to your need.
So enjoy controlling things wirelessly..