The Edwin Robotics DRV8833 breakout board is capable of controlling up to 2 DC motors or one bi/uni-polar stepper motor a max current of 1.2A. The DRV8833 comes with 2 full H-bridges which give bi-directional control of your DC motors. It is similar to the L9110S in its voltage range ( 2.7V – 10.8V), but carrying 50% more oomph. This makes it ideal for projects where the motors will be run from a 9V battery.

The board can be powered using the provided screw terminals or through micro-USB, checkout out micro-USB to DC Jack adapter if you would like to use a standard power adapter with the board

 Hardware Required

Edwin Robotics DRV8833 Motor Driver	Arduino UNO	Male-Female Jumper wires
DC Geared Motor with Wheel	9V DC Battery Snapper	microUSB to DC Jack Female Connector

Features

• Dual-H-bridge motor driver: can drive two DC motors or one uni/bi-polar stepper motor
• Operating voltage: 2.7‌‌ V to 10.8 V
• Output current: 1.2 A continuous (2 A peak) per motor
• Motor outputs can be paralleled to deliver 2.4 A continuous (4 A peak) to a single motor
• Inputs are 3V- and 5V-compatible
• Under-voltage lockout and protection against over-current and over-temperature
• Reverse-voltage protection circuit
• Current limiting can be enabled by adding sense resistors (not included)

Pinouts:

DRV8833 Motor driver pin description

 

Power

• Vm – This is the voltage supply for the motors. Keep this voltage between 2.7V and 10.8V. This Supply Pin is not Reverse polarity protected, so care must be taken while connecting jumper wires to it.
• Power Screw Terminal: The Power Screw terminal is labelled with + and -, connect your power supply according to label, this terminal is reverse polarity protected.
• USB Power In: You can power the board with micro USB connector provided; this is reverse polarity protected as well.
• GND – This is the shared logic and motor ground. All grounds are connected

Current Limiting Pins

As/ Bs: The DRV8833 can perform current limiting for each motor H-bridge by connecting a resistor between As/Bs and ground to set the Motor A/ Motor B Limit.

By default , the current limiting feature is disabled and can be enabled by modifying the jumper, refer the image below:

Current Limiting and Status LED’s Jumper Pads.

The Current limiting can be enabled by cutting out the solder joint between the jumper Pads for Asen and Bsen. Once the jumper pads are modified you can either solder SMD resistor (1206 Size) on board or you can use the AS/BS headers pin to make connection with through hole resistors. You can also totally disable current limiting whenever needed by soldering the two jumpers on the back.

The current limiting rule is: LimitCurrent (amps) = 0.2 V / RSENSE

Add 1206 resistors here to modify the current supplied to the respective motors

 

Connection’s

You can use any stepper motor or dc motor rated upto 10.8v with this board. We have used the following kit to get it tested:

Robotics Kit

 

 Refer the image below for the motor connections

Motor Connections

Power Supply Connections

Arduino DRV8833 Connections

Test Codes

#define Ain1 5
#define Ain2 6
#define Bin1 9
#define Bin2 10

int speed = 0;

void setup() {
pinMode(Ain1, OUTPUT);  //Ain1
pinMode(Ain2, OUTPUT);  //Ain2
pinMode(Bin1, OUTPUT);  //Bin1
pinMode(Bin2, OUTPUT);  //Bin2

}

void loop() {

    digitalWrite(Ain1,HIGH);
    digitalWrite(Ain2,LOW);
    digitalWrite(Bin1,HIGH);
    digitalWrite(Bin2,LOW);
    delay(700);
    digitalWrite(Ain1,LOW);
    digitalWrite(Ain2,LOW);
    digitalWrite(Bin1,LOW);
    digitalWrite(Bin2,LOW);

    digitalWrite(Ain1,LOW);
    digitalWrite(Ain2,HIGH);
    digitalWrite(Bin1,LOW);
    digitalWrite(Bin2,HIGH);
    delay(700);
    digitalWrite(Ain1,LOW);
    digitalWrite(Ain2,LOW);
    digitalWrite(Bin1,LOW);
    digitalWrite(Bin2,LOW);
  
}

Download DRV8833 Datasheet

References:

Adafruit Hookup Guide

Polulu Blog

Introduction

The MCP23S17 is a SPI Based Port Expander which can add 16 more digital I/O pins to your Arduino or Raspberry Pi. Thanks to the wide operating voltage of 1.8 – 5.5V,  you can add 5V I/O pins to the Raspberry Pi or 3.3V based Arduino thereby avoiding a level shifter and simplifying connections.

Hardware Required:

MCP23S17 Port Expander

Breadboard

Jumper Wires

Board Overview

The board consists of 2 Port Banks (A and B), a 3-way switch, power and SPI headers

3-Way switch is used to set the address of the Port Expander, the switch positioned towards ON sets the address as ‘0’. The image above sets the address as ‘7’

INT B Interrupt output for PortB

B.0 – B.7 Bidirectional I/O

INT A Interrupt output for PortA

A.0 – A.7 Bidirectional I/O

VCC Power supply pin for the MCP23S17, connect to a voltage source between 1.8V -5V

GND connect to ground of power supply

SO, SI, SCK & CS SPI Pins

RESET connect to ground to reset the port expander

Note: The silkscreen on Port A is reversed, meaning INT A actually is A.7 and A.7 actually is INT A

Enabling SPI on the Raspberry Pi

By default the SPI peripheral is not enabled, we cannot continue unless this is done first. Have a look at the tutorial by SparkFun on how to do this.

Interfacing the MCP23S17 Port Expander with the Raspberry Pi

Interfacing the MCP23S17 to the Raspberry Pi

Connections from Raspberry Pi to MCP23S17 Port Expander

Installing the Python Library

In order to get started the python library needs to be installed first. Run the following command in terminal to install the library

sudo pip install RPiMCP23S17

Sample Code

The below code will turn ON and OFF all the pins at an interval of 1 second.

from RPiMCP23S17.MCP23S17 import MCP23S17
import time

mcp = MCP23S17(bus=0x00, ce=0x00, deviceID=0x00)
mcp.open()

for x in range(0, 16):
    mcp.setDirection(x, mcp.DIR_OUTPUT)

print "Starting blinky on all pins (CTRL+C to quit)"
while (True):
    for x in range(0, 16):
        mcp.digitalWrite(x, MCP23S17.LEVEL_HIGH)
    time.sleep(1)
    for x in range(0, 16):
        mcp.digitalWrite(x, MCP23S17.LEVEL_LOW)
    time.sleep(1)

Further Reading

RPiMCP23S17 Github Repo

New to Electronics or programming ? No need to worry now, the Raspberry pi is only for you. If you are beginner, we will recommend you to go through our Raspberry Pi Blogs. We will recommend you to go through these set of videos before getting started. Lets have a look at set of contents we are covering in this tutorial.

• Hardware Needed

• Using RasPiO Portsplus with Raspberry Pi

• Getting Started With Breadboard and LED

• Getting Started with Switch, transistor and buzzer on breadboard

• Pi Wedge Hookup Guide

• Getting Started with Physical Computing on Raspberry Pi

• Getting Started with Scratch

• Test blinking LED using Python/Scratch

• Testing Switch using Python/Scratch

• Testing Capacitive Touch using Python/Scratch

• Testing Buzzer using Python/Scratch

• References

Hardware Needed

        Raspberry Pi Electronics Starter Kit

RasPiO Portsplus

The RasPiO® Portsplus board is designed for the new Raspberry Pi 3/2/A+/B+. It labels the ports clearly for you so that you don’t need to count pins. This will help you avoid wiring errors and damage.You can slip it over the GPIO header if you want, or hold it next to the header.RasPiO® Portsplus has GPIO port numbers on one side and Pin numbers on the other side, so you can use whichever numbering system you prefer. At just 1mm thick, it leaves plenty of space for attaching your wires. It’s thick enough not to feel flimsy, but thin enough not to be clunky. Refer the image below, to see how to use RasPio Portsplus.

Raspberry Pi with RasPiO Portsplus and jumpers

Breadboard and LED

In this step we will start with the breadboard, breadboards are preferred platform to start building circuits because it don’t need any soldering, thus giving you the flexibility to try, test and modify your circuit at any point of time. They allow you to make quick circuits, test out ideas and allow prototyping before making a permanent Printed Circuit Board. They are inexpensive and reusable and they are easily available in any electronics store. Once you understood the basics regarding breadboading , then will go ahead with the basic essential component of all the electronics circuit i.e LED.We have already added all the details regarding this step in the following blog, refer this blog on ” How to Breadboard LED “

Getting Started with Switch, transistor and buzzer on breadboard

One of the most elementary and easy-to-overlook circuit component is the switch. Switches don’t require any fancy equations to evaluate. All they do is select between an open circuit and a short circuit. Simple. But how could we live without buttons and switches!? What good is a blinky circuit with no user input? Or a deadly robot with no kill switch? or any remote or mobile with no buttons? What would our world be without with big red buttons.A switch is a component which controls the open-ness or closed-ness of an electric circuit. They allow control over current flow in a circuit (without having to actually get in there and manually cut or splice the wires). Switches are critical components in any circuit which requires user interaction or control.A switch can only exist in one of two states: open or closed. In the off state, a switch looks like an open gap in the circuit. This, in effect, looks like an open circuit, preventing current from flowing.In the on state, a switch acts just like a piece of perfectly-conducting wire. A short. This closes the circuit, turning the system “on” and allowing current to flow unimpeded through the rest of the system.

A circuit with an LED, resistor, and a switch. When the switch is closed, current flows and the LED can illuminate. Otherwise no current flows, and the LED receives no power.

There are tons and tons of switches out there: toggle, rotary, DIP, push-button, rocker, membrane, … the list just goes on and on. Each of those switch types has a set of unique characteristics to differentiate it from others. Characteristics like what action flips the switch, or how many circuits the switch can control. You can check the different types of switches we having with us.Transistors can be regarded as a type of switch, as can many electronic components. They are used in a variety of circuits and you will find that it is rare that a circuit built/available in school Technology Department/ Laboratory does not contain at least one transistor. Even the things you used in your daily life, i.e mobile, tv, computers, etc all comes with tons of transistors built into it, transistors are central to electronics and there are two main types; NPN and PNP. Most circuits tend to use NPN. There are hundreds of transistors which work at different voltages but all of them fall into these two categories.We had added detailed tutorial on ” Getting started with switch, transistors and buzzer on breadboard “ , so that you will clearly understand the basics of switches, transistors and buzzer.

Pi Wedge

Its time to expand your GPIO pins from the Raspberry pi and made it accessible for Breadboarding. The preassembled 40-pin Pi Wedge will let your Pi pins broken out to a breadboard so that they can easily be used. The Sparkfun has already added a detailed hookup guide on their website, we will recommend you to refer this tutorial to understand pi-Wedge better.

Physical Computing on Raspberry Pi

The Raspberry Pi learning resource is provided for free by the Raspberry Pi Foundation under a Creative Commons licence, which we are able to access from their website, you can find the resources here, We have provided all the items in the Electronics Starter Kit to get started with mentioned tutorial, all you need to do is follow the steps mentioned in the getting started tutorial to understand the basic principles  of interfacing individual items. please go through this guide on “Getting Started with Physical Computing on Raspberry Pi “

Scratch

Scratch is a visual programming tool which allows the user to create animations and games with a drag-and-drop interface. It allows you to create your own computer games, interactive stories, and animations using some programming techniques without actually having to write code. This resource will help get you started with the basics of Scratch. The Raspberry Pi learning resource is provided for free by the Raspberry Pi Foundation under a Creative Commons licence, which we are able to access from their website, you can find the resources here, please go through “Getting Started with Scratch on Raspberry Pi Tutorial” to understand the various features and application of the Scratch tool.

Blinking LED

Since you have already seen some basic programming in the getting started section, we are adding one more advancement in the LED circuit and code here, we will recommend you to build the following circuit in your breadboard:

Blinking LED Circuit

To begin with, we will recommend you to open the IDLE from the following path: Menu -> Programming -> IDLE 3/Python 3 and you will find the Scratch in the Same path as well:  Menu -> Programming -> Scratch.We had added the python code and Scratch Project in the following link, you can save/download the file in your system, click on the respective icon to open/download the file.

You can refer to scratch program in the image below:

LED Blinking

Switch

In this step you have to add switch connection to the LED connections you made in the previous step. Follow the circuit shown below:

Switch Connection

Now refer the Scratch and Python Code to get it working

You can refer the Scratch program in the blow image:

Contro LED Using Switch/Sensor

Capacitive Touch

The capacitve touch module we providing in the Kit works as momentary switch in default mode, but if need you can solder the jumper to the pads or add some conductive tape to the pads to change the mode of operation from momentary to toggle. The Capapcitive touch module is capable to sense the human touch, even it can sense the body within nearby range to the pads thus allowing you to place the pads under thin cardboards/paper/plastic, you can add copper tape to it to extend the capacitive touch area as your wish. These tiny boards are nice addon to your project. Refer the image below for the connection diagram:

Capacitive Touch Board description

The board works well with 3.3v and 5v Systems, thus giving you the flexibility to use it straight away, these boards comes with onboard LED for the indication, thus you can use it as an independent product without any need of  Microcontroller or Microprocessor. Now, refer the breadboard connection for the Capacitive touch board and the LED:

Capapcitive Touch and LED Connection with Raspberry Pi

Since we had replaced the tactile switch with Capacitive touch module in this circuit and we let the LED stay as it is like in the previous steps, thus the code which we used to control LED with tactile switch will work for this module as well.

Note: We had used GPIO pin 24 to connect Signal pin of the Capacitive touch module thus the previous code will work for this case as well, but if you had used some other pins for this module, make sure to change the pin numbering in the code as well.

If you are using the Capacitve module in Toggle Mode, try out the following code to understand the difference:

Transistor and Buzzer

Till now, you have seen the LED indication in the output side, now its time to add some sound to the circuit, since you had already worked with ” Getting started with switch, transistors and buzzer on breadboard “  tutorial, this step is going to be easy. Refer the modified breadboard connection for the circuit.

Transistor, Buzzer and Switch Interface with Raspberry Pi

We are not adding any specific code to this section because the circuit is connected to work with all the three codes described above, so we will recommend you to run all the three codes again for the above circuit, try to add and change the delay in the code, so that you can hear the variation in the output.Since you already understood the basics of various components and its interfacing and programming in scratch and python, we are giving you challenge to breadboard RGB LED we provided in the Kit and write your own Python and Scratch code for the same, to made it glow for different combination of colors.

Let us know your feedback on this and we are happy to help you, if you found any issue or difficulty in any circuit or have any queries, please do let us know.

References:

• Tutorial: How to Breadboard LED
• Tutorial: Getting started with switch, transistors and buzzer on breadboard
• Sparkfun Tutorials
• Buy Switches Online
• Buy Transistors Online
• Raspberry Pi Learning Resources

Good to see that lots of people are interested and looking forward for Raspberry pi, to have the feel of old gaming experience. We already wrote one blog on Retro Gaming machine using Raspberry pi, we mentioned there how to download RetroPie Image and ROM and Install it in your system. We will recommend you to go through Retro Gaming machine using Raspberry pi Blog

This blog is targeted towards people who might not want Raspberry pi to be dedicated just for Retro Gaming Purpose or whom already have our Raspberry Pi Gaming Kit or whom having Raspberry loaded with Raspbian. Here we mentioned steps on how to install RetroPie on a Raspberry pi running Raspbian. This setup will give you flexibility to use any one system(Raspbian or RetroPie) as per their need, i.e they can run RetroPie without uninstalling Raspbian and choose between any one at a time to work with. We will show you how to set RetroPie EmulationStation as default environment and from their if you want you can skip the RetroPie and go to either terminal or Raspbian desktop environment.

To start with, we will recommend you to have our Raspberry Pi Gaming Kit ready with you, its comes with SD Card preinstalled with latest Raspbian on it. Note: If you aren’t comfortable with the terminal you would be wise to just use the RetroPie SD image as described in this Retro Gaming machine using Raspberry pi Blog. Follow the steps mentioned to get it working.

1. Download RetroPie Setup script
2. Download and Install Putty to run Command via computer
3. Set EmulationStation as default boot option (video)
4. Download ROM
5. Install ROM
6. Configure Gamepad
7. References

1)    Open the command terminal, refer the following image if you don’t have idea where is it:

2)   Download RetroPie Setup Script: 

cd
git clone --depth=1 https://github.com/RetroPie/RetroPie-Setup.git

 

All you need to do is copy the mentioned command line by line and paste it(mouse right click) to the terminal. If you are wondering how to copy paste this, then you can either open this blog in the Raspberry pi browser or It is recommended to use putty on your computer to access the Raspberry Pi terminal.

Download and Install Putty to run Command via computer:

Download Putty from here and install it, then you need to enter you Raspberry Pi IP address in the space provided, refer the following image for the same:

Raspberry Pi IP address can be found out by running the ifconfig Command in your LX terminal. Make Sure that your Raspberry Pi is connected to Wifi or ethernet before doing this step.

3)    Once the Script is downloaded you need to execute the script as follows:

cd RetroPie-Setup
chmod +x retropie_setup.sh
sudo ./retropie_setup.sh


4)    Make sure to run command line by line as shown, refer the video shown below on how to install the RetroPie

5)   Set EmulationStation as default boot option (video):  It will take some time to install the RetroPie on Raspbian, you need to wait till then, once done, the last step you need to do is to run the script again and set EmulationStation as default in the boot option, refer the video below for the same:

6)    Once the above step is done, you can see that after the computer reboots, it will open the EmulationStation by default, if you want to access command terminal, you need to press F4 on you keyboard to exit the EmulationStation, you can type emulationstation in the command terminal to open EmulationStation back again. To open pixel desktop you need to run startx command in the terminal, it will load pixel environment for you.

Note: You cannot run EmulationStation and the LXDE/ Pixel Environment at the same time so you need to reboot your system to turn on your EmulationStation.

7)    If you are all done till previous point, now all you need to add is ROM to your system, due to the nature/complexity of Copyright/Intellectual Property Rights Law, which differs significantly from Country to Country, ROMs cannot be provided with RetroPie and must be provided by the user. You should only have ROMs of games that you own.Refer this link to see how to download ROM and Install ROM

8)    Configure Gamepad: Once you added the ROM, its time to configure your gamepad, to do so open the EmulationStation Menu( refer the below shown Image)

Select: retroPie menu -> Input options.

9)    Make Sure to connect your game pad before selecting Input options from the Menu. Once selected refer the below key map to configure your gamepad, all you need to do is to press the corresponding key for the shown input option.

Once done, the settings will be saved permanently  in your system, incase any mistake happened, you can reconfigure your gamepad anytime. Refer this link, if you are planning to add some other gamepad to your raspberry pi, once done you are ready to control your EmulationStation and play games using your gamepad.

Note: Only one input is supported for single player games, thus if you had connected multiple inputs like keyboard and gamepad, make sure to disconnect whichever not needed and connect only one.

Do let us know if you are facing any issue with any step, our team will get back to you, to help with installation.

References:

• Buy Raspberry Pi Compatible Gamepad
• Updating RetroPie
• RetroArch Configuration
• FAQ

Missing the old classic games and your gaming consoles? No need to worry now, we are writing this tutorial for you only, if you have Raspberry pi lying around you, then get ready to turn it into a gaming machine. Before going further some of you may be confused with what Retrogaming is all about, for those let us clear something, you might have seen people playing mario the popular classic game using older gaming consoles that is something which comes under retro games, Usually retrogaming is based upon systems that are obsolete or discontinued.

Here in this post what we are showing  “how to turn your Raspberry Pi into an retro gaming machine”, for this we are going to use RetroPie. RetroPie allows you to turn your Raspberry Pi or PC into a retro-gaming machine. It builds upon Raspbian, EmulationStation, RetroArch and many other projects to enable you to play your favourite Arcade, home-console, and classic PC games with the minimum set-up. For power users it also provides a large variety of configuration tools to customise the system as you want.

RetroPie sits on top of a full OS, you can install it on an existing Raspbian, or start with the RetroPie image and add additional software later. It’s up to you. You can follow our RetroPie Installation guide to install the RetroPie on an exsiting Raspbian or If you had bought our Raspberry Pi Gaming Kit, you can refer this blog to setup your RetroPie and Configure the Gamepad we provided.

• Hardware Needed

• Installation

• Installing ROM

• Download ROM

• Configure Gamepad

• References

Let us have a look at the hardware needed for this:

1. Raspberry Pi (A, A+, B, B+, 2, Zero, or 3) – for best performance use a Raspberry Pi 3
2. Power Supply
3. SD Card
4. Raspberry Pi official case- White (Optional but recommended)
5. Keyboard*
6. Mouse*
7. USB Joystick /GamePad*
8. Wifi Dongle or Ethernet Cable (Wifi is built into the Pi 3)
9. Display/Monitor with HDMI Cable.

* Either the keyboard and mouse or the USB Joystick/GamePad is require to be able to play

You can straight away start with our Raspberry pi 3 Gaming Kit Black or Raspberry Pi 3 Gaming Kit White. If you having our Raspberry Pi Gaming Kit with you or you are looking for Configure our Gamepad alone, you can refer this blog

Installation

Now once you are ready with the mentioned hardware, its time to setup your SD card with RetroPie, for this you need to download RetroPie OS. There are currently two versions of RetroPie. There is one version for Raspberry Pi 0/1 (Model A, A+, B, B+) and there is a version for Raspberry Pi 2/3.

Download the SD image for your version of Raspberry Pi from the following page:

https://retropie.org.uk/download/

If you are unsure which version of Raspberry Pi you have then look at the Silkscreen on the Raspberry Pi, its mentioned there or if you having one running raspberry pi with raspbian installed then there is an easy way to check:

Rpi 0/1= 1 raspberry when the pi boots up

Rpi 2/3= 4 raspberries when the pi boots up

The above mentioned things can be confirmed after you install the RetroPie on your Raspberry pi. If you get the error Illegal Instruction when it boots, you picked the wrong SD image.

Once you have downloaded your SD card image you need to extract it using a program such as winrar or 7-Zip. You will extract the downloaded .gz file and the extracted file will be a .img file.

To extract from the command line, you can type the following into a Terminal window, placing X with version you downloaded:

gunzip retropie-4.X.X-rpi2_rpi3.img.gz

To install the RetroPie SD image on your MicroSD card. (You may need a MicroSD card reader to plug it into your computer)

1. For Windows you can use a program called Win32DiskImager
2. For mac you can use Apple Pi Baker
3. For Linux you can use dd command or Etcher

Refer this guide to see how to install using Win32DiskImager.

Once you done with writing image to your SD card, you are ready to plug in the card to Raspberry Pi and Power it up.After your power the system you will see screen as follows:

Here you are able to configure your gamepad and keyboard key function, all you need to do is follow the onscreen command, the above shown screen will come during the first time setup only, otherwise, the system will boot retroPie EmulationStation( refer the image shown below), the configuration can be done at anytime as well, which is available in retroPie menu -> Input options.

Now what you can see in front of you is the EmulationStation, when you first see EmulationStation you may wonder why you don’t see systems like the SNES or Game Boy- worry not- they are installed on the system, roms just need to be added to their respective rom folders before they will become visible. Transferring roms are described in the following steps:

Installing ROM

Due to the nature/complexity of Copyright/Intellectual Property Rights Law, which differs significantly from Country to Country, ROMs cannot be provided with RetroPie and must be provided by the user. You should only have ROMs of games that you own.

You can transfer the ROMs using USB or using SFTP . Refer the steps below to install using USB

• (ensure that your USB is formatted to FAT32 or NTFS)
• first create a folder called retropie on your USB stick
• plug it into the pi and wait for it to finish blinking
• pull the USB out and plug it into a computer
• add the roms to their respective folders (in the retropie/roms folder)
• plug it back into the raspberry pi
• wait for it to finish blinking
• Refresh emulationstation by choosing restart emulationstation from the start menu

To transfer ROM using SFTP, follow the mentioned steps:

• Connect you Raspberry pi to network, connect ethernet cable to your pi for a wired network or you can use built in wifi for the Raspberry pi 3 or use wifi dongle for older Raspberry pi.
• To connect your Raspberry pi with wifi, you need to boot the Raspberry Pi(except Raspberry pi 3) without the WiFi adapter plugged in.
• Skip the Emulator screen which is shown in the emulator image by pressing F4 on keyboard then you will be directed to command line
• Then enter followng command:
  

  sudo nano /etc/network/interfaces

• Then you will see following file:

auto lo

 

iface lo inet loopback

iface eth0 inet dhcp

 

allow–hotplug wlan0

auto wlan0

 

 

iface wlan0 inet dhcp

wpa–ssid “ssid”

wpa–psk “password”

• All you need to do is replace the ssid and password of your network and save the file and you will be connected to wifi automatically once you reboot the system.
• The other way to connect  is to use the RetroPie EmulationStation itself, once you open the RetroPie you will see the option for wifi, all you need to do is enter the credentials.
• Once connected note down the IP address of the System, you can find it in the same page where you find the Wifi option in the EmulationStation.
• There are many SFTP programs out there, for windows many people use WinSCP and for mac you can use something like Cyberduck
• We will show you how to install using WinSCP, first install WinSCP and enter the following credentials in the Login Window:

Host Name: Your IP Address

User name: pi

Password: raspberry

Once you are logged in successfully, you can see two windows, one window as your computer files explorer and the second window is of RetroPie files explorer, you just need to upload the files from your computer to the RetroPie -> ROM -> Emulator(for the Respective ROM you having) directory. Refer the sample video below for the demonstration we did to transfer one configuration file from windows system to other System.

Download ROM

If you don’t have any ROMs with you, download some from here

You can see that games for various emulators are provided in the website, you can download any game for the supported emulators you needed. Refer this link to see the list of supported systems/Emulators for RetroPie. Now follow the steps below:

• For initial test open the Atari2600 Emulator and there you can see a list of games, download anyone game as per your interest.
• Once downloaded extract the files to some known location like your computer desktop. once done you can see one file in the desktop with .A26 Extension
• Now open your WinSCP and connect with RetroPie
• Once connected, open the rom folder under RetroPie
• Open the Atari2600 folder mentioned under rom directory
• Copy the file from your computer desktop to the Atari2600 Folder.
• Now all you need to do is disconnect the WinSCP and restart your RetroPie and you are ready to play your game.

Before playing make sure, you had configured your gamepad/Keyboard, for reference check this installation guide and check out the key Maps for the gamepad. Hope you had enjoyed this tutorial, we love to hear from you.

Stay tuned for our brand new RetroPie Starter Kit for Raspberry Pi, which will be launched soon.

References:

• RetroPie Install Guide
• retropie.org
• Retropie Download
• Wikipedia
• Beginner Installation video
• RetroPie Supported Systems/ Emulators
• ROMs
• Github

Confused with which Raspberry pi starter kit to go for ? Don’t worry, we came with this selection guide to select the starter kit as per your need. If you had visited our store, you may seen that we have variety of starter kit in our store and there are chances that you may get confused with, what are difference between these starter kit?

This guide is mainly focused on Raspberry Pi starter kit on the Edwin Robotics Online store, let us show you what are the different starter kit we have in the store:

• Raspberry Pi Zero Budget Pack – Includes Pi Zero v1.3

• Raspberry Pi 3 Media Center Kit – White

• Raspberry Pi 3 Media Center Kit – Black

• Raspberry Pi 3 Starter Kit – White

• Raspberry Pi 3 Starter Kit – Black

These are the kit we offer for the Raspberry Pi. Let us see what are the differences between these kits:

Raspberry Pi Zero Budget Pack – Includes Pi Zero v1.3

This is the only kit we offer for the Raspberry Pi zero. Users who are willing to build projects using Raspberry Pi Zero, this budget pack is best suitable to start with. The Kit consist of following items:

• Raspberry Pi Zero – the type of low cost game-changing product Raspberry Pi’s known for – a super light, super lean microcomputer
• Mini HDMI to HDMI Adapter – Will let you convert the little port on the Zero to a standard sized HDMI jack. You can get 1080P HDMI video + audio out of this little computer!
• USB OTG Cable – Lets you plug in a normal USB device such as WiFi dongle, USB hub, keyboard, mouse, etc into the Zero.
• 8GB Class 10 SD Card – A SD card that’s perfect for burning Raspbian Jessie for the Pi Zero
• 5V 1A Power Supply & USB A/Micro B Cable Or 5V 2A Power Supply w/ Micro USB Cable – the best way to power up your Pi Zero with a stable 5V power supply that wont vary or sag.
• 2×20 Male header strip – Solder this in to plug in Pi HATs, GPIO cables, etc as you would into a normal Pi.

Now, leaving aside Raspberry Pi zero, we have four varieties of kit available for Raspberry Pi 3, Refer the below table to check the contents under each kit:

	RetroPie Gaming Kit Black/White	Starter Kit Black/White	Media Center Kit Black/White
Raspberry Pi 3
5V 3A Power Adapter
Official Case
USB Game Controller
Heat Sink
Mini IR Remote
microSD card (16GB, Class 10 )	OSMC	Raspbian	Raspbian

Refer the following points to be noted from the table

• Raspberry Pi 3 is common in all the kits
• 5v, 3A power supply Adapter is common in all the Kits
• Official black case are highlighted black. Same black case is available in both the kits
• Same Official White case is available in both the kits
• Media center Kit comes with IR Remote and receiver, whereas Starter kit comes with Heat sink for the Raspberry Pi 3
• Media Center Kit is loaded with Open source media center configured for the IR remote we providing.
• Starter Kit is loaded with latest Raspbian OS with default firmware updates.

Thus, the Media center Kit and Starter Kit comes with two different OS for different purposes. If you are looking to dedicate your Raspberry pi for music, videos, movies, internet, then we will recommend you to go for media center kit which is loaded with OSMC, OSMC (Open Source Media Center) is a free and open source media player based on Linux. OSMC is the leading media center in terms of feature set and community and is based on the Kodi project. Refer our blog on Media center for better idea on OSMC capabilities.

If you are looking to build some projects using raspberry Pi, sensors and I/O devices, then use our Raspberry pi starter kit, which is loaded with Raspbian, Raspbian is a free operating system based on Debian optimized for the Raspberry Pi hardware, it comes with over 35,000 packages, pre-compiled software bundled in a nice format for easy installation on your Raspberry Pi.
We hope, now things are more clear to you. Click the links below to order kit based on your requirement:

• Raspberry Pi Zero Budget Pack – Includes Pi Zero v1.3

• Raspberry Pi 3 Media Center Kit – White

• Raspberry Pi 3 Media Center Kit – Black

• Raspberry Pi 3 Starter Kit – White

• Raspberry Pi 3 Starter Kit – Black

If you are willing to order one customized kit as per you requirement, Contact us with your requirements.  we will get back to you as early as possible.

Want to check if you left your lights ON remotely, need to detect the zero crossing point for your dimming circuit or do you just need to interface a 230V signal to your Arduino? The AC Mains Detector board simplifies interfacing high voltage signals by giving a digital output when an AC voltage is detected. By disabling the on board capacitor, zero crossing detection is possible as well.

AC Line detection Module

You can buy this item from the following links:

Within GCC: Edwin Robotics

International Order: Tindie

Let us have a look at the guide contents, refer to the list below:

• Components

• Board Pinouts

• Circuit Schematics

• Interfacing with Arduino

• Zero Crossing detection using Arduino

Components

AC Line detection Module

Arduino UNO

Male-Female Jumper wires

Board Pinouts

Top Side

Bottom Side

• AC-IN – Connect the AC line that needs to be detected here.
• – (negative sign) – Connect to ground of microcontroller
• + (positive sign) – Connect to VCC of microcontroller in case external pull-up is required
• S – Connect to a digital/interrupt pin of microcontroller

Note: Working with AC voltages is DANGEROUS, care must be taken to prevent any short circuits or mistakes in connection. And as always, you are doing this project at your own risk and Edwin Robotics or the Author cannot be held liable for any damages.

Circuit Schematics

The circuit consists of two main parts, first is the Bridge Rectifier (DB107) which converts the AC signal to DC and the second is the Optocoupler (LTV816), which provides isolation between High voltage(HV) side and Low Voltage (LV) Side.

A pull-up resistor is provided for use with microcontrollers (e.g. ESP8266) that do not have an internal pullup resistor.

Interfacing with Arduino

The hardware connections are pretty straightforward. On the low voltage side the + (positive symbol) goes to VCC of microcontroller, – (negative symbol) goes to GND and S goes any digital/interrupt pin. On the high voltage side, the AC lines are connected.

Arduino Connections

In this example, Pin 2 on the arduino is used in this example as it can be used as an interrupt pin as well.

Sample Code:

#define Signal_Pin 2  // Modify this pin as per your connection

void setup() {
  pinMode(Signal_Pin , INPUT_PULLUP);
  Serial.begin(9600);
}

void loop() {
  if ( digitalRead(Signal_Pin) == 0 )
    Serial.println (" AC Mains 230v Detected ");
}

Note: Do not touch the PCB once powered, you can get electrocuted. Keep it away from reach of humans/Animals. Make sure that there are no shorted wires, when connecting the 230v AC mains supply.

Zero Crossing Detection using Arduino

By default zero crossing detection is disabled by the use of a 2.2uF capacitor, in order to use the board for zero crossing detection the capacitor needs to be bypassed by cutting the trace shown below. It can be resoldered at any time later to disable zero crossing:

Modify the jumper

The Arduino connection will be same as before, upload the following code and view the output on Serial Monitor at 9600 baud rate:

#define Signal_Pin 2 //Use Arduino Pin 2 or pin 3, both supports hardware interrupt
int counter=0;

void setup()
{
  pinMode(Signal_Pin , INPUT_PULLUP);
  Serial.begin(9600);
  attachInterrupt(0, zero_crosss_int, RISING);  // Choose the zero cross interrupt # from the table above
}

void zero_crosss_int()  // function to be fired at the zero crossing to dim the light
{
  counter++;
}

void loop()
{
  Serial.println(counter);
}

You can see that the counter value increases with every cycle of AC line and the moment you turn off the AC line, the counter Stops as well.

References:

• DB107 Rectifier Datasheet
• LTV-816 Datasheet

Have you ever felt that, you need a dedicated Media center to take your entertainment to next level. Then try our Media Center Kit, this guide will help you to set up your own media center, also we have added guide in the section below to control this media center using any IR remote and playing and controlling photos and videos from your smart phones.

This Media Center allows you to view free digital TV Shows, Music, Sports and much more direct from the Internet. You can play any of your unencrypted digital movies and music from USB storage devices or connecting to your network drives. You can stream movies, and manage your media library, all with full iOS and Android compatibility.

The SD card is loaded with OSMC, OSMC (Open Source Media Center) is a free and open source media player based on Linux. OSMC is the leading media center in terms of feature set and community and is based on the Kodi project. OSMC can play all major media formats out there and supports a variety of sharing protocols so you’re guaranteed to be able to stream from other devices. OSMC can stream media and serve files to other devices as well. It looks fantastic,
a great deal of love and care has been put in to engineering OSMC to be the best media center out there. OSMC’s look and feel is no exception. OSMC is more than just a media center, it’s an experience. Don’t take our word for it though. Give it a spin!

Let us have a look at the guide contents, refer to the list below:

• Package Contents

• Hardware Connections 

• Setting up Network Connections 

• IR Remote Configuration

• Playing photos and videos from smart phone

• Using Kore/Yatse as OSMC remote

• Raspberry Pi Media Center Installation Manual

Package Contents

• Raspberry Pi 3
• Official Raspberry Pi Case
• SD Card with OS
• Power Supply 3A
• Mini IR Remote Control

One more variant of the mentioned kit is available, check it out here. The only difference between the two is the Raspberry Pi official Case. One kit comes with Grey-black case and the other kit comes with white case.

Hardware Connections

The connections are really simple, we had provided all the parts and accessories to get it running. you need to connect following two things to start with media center:

1. HDMI Cable
2. Power Supply 3A

The HDMI cable from the TV / Monitor/ Display must be connected to the Raspberry Pi HDMI Port in order to see the display. Once you done connecting your HDMI, plug in the SD card we provided and then connect the power supply cable to the micro USB port. Refer the Image below for better idea.

Once you done with connecting the power adapter and HDMI cable, you need to either connect the USB keyboard/Mouse to the USB port or connect the IR remote receiver we provided in the kit before powering up the device. No need to add or install any drivers or configuration file, all you need to do is to connect hardware properly. Follow the below image to connect your IR Receiver to the Raspberry Pi.

Once you done with above mentioned connections, you are ready to go, now you are able to control your media Center just using the IR remote we Provided. Refer the Key functions in the image below, you are free to modify these key functions, we will show you how to modify these key functions at later stage.

By default the OSMC outputs the audio through HDMI cable itself, thus there is no need to connect any other cables or wires for the audio, but in case you need to connect your headphones or speakers, you need to connect 3.5mm audio cable to the audio jack. The Audio Jack is present next to the HDMI port. We had set the default audio output option as HDMI and Analog, thus you are able to listen audio from HDMI as well as audio jack at the same time, you are able to change and modify these audio settings anytime. you can find these settings under:

System Settings  ->  System  ->  Audio output

Once you open the mentioned tab, you are able to see the page as shown in the image below. This page refers to audio settings, which you can modify as per your requirements.

We had set the OSMC skin as default, if you are using the same skin, you can see the same as shown in the above image, but if you had modified the Skin from OSMC to confluence then you can see the same window as shown in the image below.

Setting up Network Connections

The OSMC comes with Network Interface GUI, where you are able to change the settings for multiple network related devices. All you need to do is open the following path in the OSMC

My OSMC  ->  Network

Refer the video below for the same:

If you look at the available options, you can see following options:

• Wired
• Wireless
• Bluetooth
• Tethering
• MySQL

Under each tab you can see the enable and disable keys and you can use connect and disconnect to make connectivity with any of the Wifi access point or Bluetooth devices or even you are able to set the Pi as hotspot too under the tethering tab. The GUI is so simple and easy to understand, you will hardly face any issue connecting the media center to your network. Make Sure that you enable the adapter under the Wired tab, if you are using Ethernet cable for network connectivity.

IR Remote Configuration

This section will help you to add new IR configuration to the OSMC. Right now we had configured the OSMC with the remote we provided but you are able to use any IR remote around you to control the media center, all you need is to add the configuration file to the OSMC system and set that configuration file as preferred file for IR remote.

Since OSMC is Linux based, we are going to use  LIRC  “Linux Infrared Remote Control”, LIRC is a package that allows you to decode and send infra-red signals of many (but not all) commonly used remote controls. Under this we are going to use LIRCD System Administration Utilities, its capable to decode infrared signals and provide them on a socket.

If you are using standard remote like Samsung, sony, apple, etc. You have to download the configuration file for the same and needs to add it to the OSMC.

Use this Link to find your remote, here you can find most of the LIRC config file for most of the standard remotes.

LIRC Configuration files for standard remotes

You can download the files to your computer. In this tutorial we used windows computer. Once you done with downloading, you need WinSCP (SCP, FTP Client for windows), download winSCP from this Link, once you done with installation you need to connect to OSMC via network IP address, refer the image below to check your IP address:

Once you find out the IP address, enter the following credentials in the Login Window:

Host Name: Your IP Address

User name: osmc

Password: osmc

Once you are logged in successfully, you can see two windows, one window as your computer files explorer and the second window as OSMC files explorer, you just need to upload the files from your computer to the OSMC. Refer the video below for the demonstration we did to transfer one configuration file from windows system to OSMC.

In the video shown, you have noticed that there is already one ER-lircd.conf in the OSMC, this is the configuration file we used for our remote, then we shown how to add one other configuration file to the OSMC, we dragged the ER-lircd-temp.conf file from windows desktop to OSMC.

Once you are done with uploading file to the OSMC, you can close the WinSCP, now all you need to do is to select the configuration file for your remote from the system directory, we had added one video for the same, where we are adding configuration file for the remote we provided.

OSMC LIRCD CONFIGURATION

This is one way of adding remote to your media center, now there are chances that you are not able to find configuration files for your remote, or you are using universal remotes or you want to modify the existing configuration file, in that case, you need to manually make configuration file for your remotes, it means you need to record each and every key on the remote whichever you want to be functional. Follow the steps to record your keys:

• Stop the LIRCD service
• Start Recording
• Assigning standard functions to Individual Keys on the remote
• Save and load the Configuration file

Stop the LIRCD Service

Before you start with this step, you need to download putty  . once you done with downloading putty in you computer, you are able to login to your OSMC command shell, you need to login to your OSMC system using IP address(The steps to find IP address mentioned above), enter the username and password as osmc. Once you are connected you need to run the following command to stop the LIRCD service on the OSMC.

sudo systemctl stop lircd_helper@lirc0

The above steps ensures that service is stopped and we can proceed with recording key strokes.

Start Recording

Your need to use following command to start with recording.

irrecord -d /dev/lirc0 /home/osmc/lircd.conf

This steps lets the LIRC decoder, to decode the format of the remote. During the process you need to keep pressing all the keys and follow the instructions which will be displayed in the command line. You can refer the video below for all the process we went through.

Assigning standard functions to Individual Keys on the remote

Once the LIRCD understands the remote format, the next step is to assign the name and functions to each key on the remote. You have to follow the standard configuration file for this step, as the names are standard and the LIRCD won’t accept any other names, so you have to refer the one of the available standard config files, we have already provided the Link for the same in the above section.

Watch this video to see, how to record and assign functions to the remote keys.

Save and load the configuration file

If you had followed the video, you have seen that you need to hit enter at the end of recording process, to save the file. If the message “Successfully written config file” does not comes up , no need to worry about it, the file will be saved in the /home/osmc/ directory. You can use the nano editor to check the contents of the file. Use ” sudo nano /home/osmc/filename.conf ” Command. Make sure that you had replaced the filename with what you have provided.

To load the  configuration file, you need to watch the video above tagged with: OSMC LIRCD CONFIGURATION once done with all these steps you need to reboot the system.

Playing Photos and videos from Smartphone

The cool thing with this part is you are able to play your mobile contents in the OSMC player or vise versa, all you need to do is to change some settings in the OSMC to use this feature and install the BubbleUPnp from the play store. The BubbleUPnp comes in paid and free version, we tried this feature with free version.

To establish UPnp between OSMC and your mobile phone, you need to enable the UPnp services in the OSMC.

Open the following the path:   System Settings  ->  Services 

Once you are open the services you will see the following options:

• General
• UpnP/DLNA
• Web Server
• Remote Control
• Zeroconf
• AirPlay

General : Under this tab you can modify the device name

UPnp/DLNA: Under this you need to enable both the options to allow remote controlling and sharing the libraries

Web Server: This is by defualt enabled, if not please enable it.

Remote Control: Enable both the options to allow remote controlling

Zeroconf: This is by default enabled, if not please enable it.

Airplay: This you can enable if you having Apple product with you.

Now in the mobile application part, all you need to do is to expand the Renderer tab, under that you are able to list your OSMC, just connect it and you are ready to go.

To play the content from Mobile:

• Select Local Media Server under Library tab
• Expand Media tab to select from a list of available options.

Play any video/ Music from the media and you are able to watch it now on the OSMC.

Install BubbleUPnP from Google Play

Using Kore/Yatse as OSMC Remote

There are lots of remote control applications are available for the OSMC/KODI/XBMC. All you need to do is to download the application from the play store, once done with installation, the remote will look for available media center on the network, make sure that your media center is connected to network, then you will see that, these apps will comes with OSMC option. You need to select the device from the available option and then you are ready to control your media center from your mobile Apps.

We tried and tested out both the Kore and Yatse App with OSMC and its works out really well with it.

Install Kore from Google Play

Install Yatse from Google Play

To understand transistor better we will start with one of the basic component we seen in electronic circuit, its nothing but switch, refer the image below:

These switches are nothing but momentary push buttons, means when you press them then only it will be functional(i.e ON) otherwise it will remain OFF. Lets build a simple circuit on breadboard using a switch, refer the image below to build your circuit:

Note: We had Connected 5v supply and GND from Arduino board in the above image, you can use Raspberry Pi or any other boards you having with you to supply 5v and GND from the board. If you having our Raspberry Pi Electronics Starter kit with you, then you can use the RasPiO Portplus we provided with the kit, to find the 5v and GND pins on Raspberry Pi and use the Male-Female Jumper wire we provided in the Kit to Supply power to the LED-Switch Circuit on breadboard.

Now if you see, you can understand that this circuit is nothing but modification of the previous LED breadboard tutorial, here we have added one switch to the LED circuit. Care must be taken when you connect the switch. Out of four legs you will get two shorted legs, as described in the image, you refer the cut mark on the bottom of the switch to understand which sides of the switch are shorted. Make sure that the mark on the switch and the breadboard columns should match otherwise your switch will not functional properly.

When you power the above circuit, the LED won’t glow, its because the circuit is controlled by Switch now, so if you press the Switch now, you will see that the LED will remain On till the moment you press the Switch, otherwise it will remain off. The transistors works in similar fashion, its works as Switch, except that, with switch you need to use your hands to push it and made the LED glow, here with transistors you need to apply logics to turn the LED ON and OFF. Thus applying logic’s will simulate the key press in the transistor.

All the Electronic Components runs on two logic’s only 1(HIGH) and 0(LOW), When you apply Logic High to transistor the transistor will either turn ON or turn OFF depending on the transistor type. Before we see the types, we will clear you what this Logic High and Low Means. Any Electronic Machine understands only two voltages/ Logic’s and they are  Vcc/ Logic 1(High) and Gnd/ Logic 0(LOW)

Now, we will see what are types of transistor:

1. NPN
2. PNP

The NPN is nothing but N-Type transistor, which will activates when you supply a Logic High to it. Similarly, The PNP is nothing but P-Type transistor, which will activates when you supply a Logic Low to it.

Refer the two different types of circuit shown above, you will clearly understand the difference between the two types of transistors working. The P type will turn on the LED when you applied Logic low to the transistor and the N type will turn on the LED, when you apply Logic High to the transistor.

Note: The logic’s will be applied to base/gate Pin of transistors, the other two pins are emitter/drain and Collector/source.Collector/Source pin used to connect the transistor from power source and emitter/drain pin used to connect with loads.The Pin descriptions are mentioned in the datasheet of each transistor, so there is no need to worry about it as of now.

Now we will move one step further and add some sound to the project, till now when we press the switch or apply the logic’s to transistor the LED will lit up. let us add one piezo buzzer to the breadboard and see what happens when we press the switch.

Refer the schematic below to build your own circuit in a breadboard.

In the above shown example we had used Arduino as 5v power source to power the breadboard, you can use any other power source as per you convenience. Now if look at the circuit we had Used N-type(NPN) transistor, now if you google for BC547 Datasheet, you will see lots of options, open any one datasheet .pdf document, once you scan through all the pages you will notice lots of details about transistor is mentioned in it, right now we are focusing on the type, voltage and current of the transistor. If check you will see all these data  withing the first 5 pages. There its mentioned:

BC547

• NPN Epitaxial Silicon Transistor
• Vceo: 45v
• 100mA

we seen that its N-Type(NPN) and its maximum voltage is 45v which is more than enough, since we are running only on 5v. Regarding current, if we calculate the current required for the loads, the LED needs 15mA and the buzzer needs 40mA max, thus combining two, its comes under 60mA, thus we are good to go with same transistor. If your loads exceeds the rated current go for higher current transistor. Refer the image below for the Pin description of the BC547 Transistor we are using.

You can see that we are supplying High Logic from switch to transistor, so when you press the switch the Vcc(5v) will be applied to gate pin of transistor and this will activate the transistor, allowing the current to flow through LED and Buzzer and in return we can see and hear the light and sound respectively.

Note: Don’t forget to add current limiting resistor for buzzer and resistor and polarity of the buzzer must be taken care of similar to that of LED.

So, this is all about the welcome little step you made into hands on with electronics, in the next tutorial, we will show you how to use microcontrollers/Arduino to control these kind of circuits.

Breadboard is nothing but a plastic base with lots of holes in it, where you can fit in your components and wires to build your circuit. You can’t see what’s going inside the breadboard, but inside its nothing but many strips of metal that connect the rows and columns together. These metal strips are springy so that when you poke a wire or component into the hole, the clips grab onto it.

Breadboards are used for both the simplest circuit as well as very complex circuits. In case one breadboard can’t accommodate your circuit, you can snap in multiple breadboards together to make a big breadboard base. You can use breadboard to test and figure out the working of Integrated circuits (ICs).

If you refer the description in the image above you can see that the how tracks are connected inside the breadboard. Refer the Vcc and Gnd Lines in the image above, you can see these two lines are running round the borders, thus allowing us to use these lines for power supply distribution, but there is a discontinuity in Vcc and Gnd tracks as shown above(mentioned “Not Connected”), which you need to connect with jumpers to distribute the power. The center holes are column connected as shown in the picture and there is a gap in between the same columns, allowing us to fit in IC to the gap. To make things further clear, we have added the tear down image of the breadboard, refer the next diagram to get better idea of inside connections.

The image shown above is of Half sized breadboard, thus don’t be confused comparing it with previous images. Hope things are clear to this point and you understood the breadboard well, now we will move further and see how to start building basic circuits on this breadboard. We are going to start with LED circuit, which is common to all the devices, we are going to build a circuit for Power LED Indication, i.e whenever there is power in the circuit, this led will let us know about it.

If you notice the above image you will see the legs of LED mentioned with Anode and cathode and to understand how to distinguish between anode and cathode pins, we provided hints in the image, its nothing but one cut mark(Means the LED is not completely round from the bottom side) which indicates that the leg underneath it is cathode(-ve) pin and if we seen the size of the legs, the anode(+ve) pin is little longer. But most of the times you have to trim the legs of LED when you use these LED in any circuit thus making the anode pins and cathode pins indistinguishable in terms of Leg size.

The importance of anode and cathode pins in LED is that, LED will glow only is you provide +ve power supply to Anode pin and –ve power supply to Cathode Pin. But wait, you cannot straight away supply the LED with power supply because there are chances that more current will pass through LED and this will lead to damage the LED, to avoid this situation, it is strongly recommended to use the resistor along with LED.

The circuit will be something like shown above. But it is really important to use the correct resistor value in the circuit to limit the current. We will show you how to select the correct resistor value for each circuit. For this, you need to understand two necessary parameters of LED, i.e LED Current and LED Forward voltage, refer the section below, for detailed description:

LED Current:

As an example we will refer the datasheet for Basic Red 5mm LED.Starting at the top and making our way down, the first thing we encounter is this Absolute maximum ratings table:

Confused?  Questions coming that what does it all mean? right ?

So, the first row in the table indicates how much current your LED will be able to handle continuously. In this case, you can give it 20mA or less, and it will shine its brightest at 20mA. The second row tells us what the maximum peak current should be for short bursts. This LED can handle short bumps to 30mA, but you don’t want to sustain that current for too long. This datasheet is even helpful enough to suggest a stable current range (in the third row from the top) of 16-18mA. That’s a good target number to help you make the resistor calculations we talked about.

The following few rows are of less importance for the purposes of this tutorial. The reverse voltage is a diode property that you shouldn’t have to worry about in most cases. The power dissipation is the amount of power in milliWatts that the LED can use before taking damage. This should work itself out as long as you keep the LED within its suggested voltage and current ratings.

LED Forward Voltage

Now, when you check the datasheet further, you will come across the next table shown as follows:

Now,this is a useful little table! The first row tells us what the forward voltage drop across the LED will be. Forward voltage is a term that will come up a lot when working with LEDs. This number will help you decide how much voltage your circuit will need to supply to the LED.You need to follow the following formula every time you build circuits something with LED, refer the section below:

The basic ohm’s law states that:

V = I x R    or   R = V/I

where,

V = Supply Voltage

I = Current through LED

R = Circuit Resistor

Thus, applying this law for LED circuit, we will get following formula:

Where,

V_S = Source voltage (usually a battery or power supply voltage)

V_F = LED’s forward voltage

I_F = Desired current that runs through it.

For example, assume in this example you have a 9V battery to power an LED. If your LED is red, it might have a forward voltage around 1.8V. If you want to limit the current to 10mA (or 0.010A) rather than limiting it to 20mA , use a series resistor of about 720Ω.

Now, if we are going to build power supply Indicator circuit for 5v system, thus our resistor calculation will come somewhat like this:

R = (5-1.8)V ÷ 0.010A

R = 3.2V ÷ 0.010 A

R =  320 V/A

R = 320 Ω

R = 330Ω Approx (Nearest standard resistor value)

Thus if you notice in the circuit shown above, you will see that we had used 330Ω resistor in the circuit, but wait you may be confused with how the resistor shown above is 330Ω, its again you need to follow the ring colors on the resistor surface. Refer the image below for better idea:

If you notice in the image, it is well documented how the 330Ω value is calculated. Refer the formula shown on the image, which will help you to find out the resistance value of the resistor, you just need to substitute the A,B,C and D value in the formula based on the colored ring.

In our case the resistor colors are orange, orange, brown, gold in sequence, thus if we substitute the corresponding values of the colors in the formula, yow will get: 33 x 10, which is nothing but 330 with 5% tolerance, tolerance will let you know how good the resistor is?

In this case its 5% means: The resistance value is limited within the vast range [270 – (5% of 270)]  and  [270 + (5% of 270)], which is not good, the lesser the range, the more close the resistance to the desired resistance value.

Let start assembling the circuit in the breadboard, refer the image below for better idea:

Now, you can see how we utilized the breadboard columns which are internally shorted to connect the LED anode pin with resistor, similarly we used the jumper wires to connect the LED cathode pin and resistor other end. Now if you power the above shown circuit, i.e Red wire with 5v and Black with Ground supply, you will see that your LED will glow safely.

Note: We had Connected 5v supply and GND from Arduino board in the following image, you can use Raspberry Pi or any other boards you having with you to supply 5v and GND from the board. If you having our Raspberry Pi Electronics Starter kit with you, then you can use the RasPiO Portplus we provided with the kit, to find the 5v and GND pins on Raspberry Pi and use the Male-Female Jumper wire we provided in the Kit to Supply power to the LED on breadboard.

Now, we want you to build one circuit on your own with multiple LED’s in series, but before doing that, we want to clear some basics related to building such circuits. When you went through LED forward voltage section above, you seen the table with LED forward voltage, you must use that value to find out how much LED you can use in your circuit. When using multiple LED’s in series, always remember that the Forward Voltage of all of your LEDs added together can’t exceed your system voltage. This is because every component in your circuit has to share the voltage, and the amount of voltage that every part uses together will always equal the amount that’s available. This is called Kirchhoff’s Voltage Law. So if you have a 9V power supply and each of your LEDs have a forward voltage drop of 2.4V then you can’t power more than three at a time.

Kirchhoff’s Laws also come in handy when you want to approximate the voltage across a given part based on the Forward Voltage of other parts. For instance, in the example we just mentioned there’s a 9V supply and 3 LEDs with a 2.4V Forward Voltage Drop each. Of course we would want to include a current limiting resistor, right? How would you find out the voltage across that resistor? It’s easy:

9 (System Voltage) = 2.4 (LED 1) + 2.4 (LED 2) + 2.4 (LED 3) + Resistor

9 = 7.2 + Resistor

Resistor = 9 – 7.2

Resistor = 1.8

So there is 1.8V across the resistor! This is a simplified example and it isn’t always this easy, but hopefully this gives you an idea of why Forward Voltage Drop is important. Using the voltage number you derive from Kirchhoff’s Laws you can also do things like determine the current across a component using Ohm’s Law. In short, you want your system voltage equal to the expected forward voltage of your combined circuit components.

Hope the things are more clear to you now and this is the end of your first basic steps towards hands on with electronics. Refer the next tutorial for more advanced Projects.