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

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.

Most of the system either works on 5v or 3.3v and if we powered these devices straight from 9v battery, chances are there that it will damage the devices. In these case a voltage regulator will comes handy. There are different kinds of voltage regulators available in the market and based on your application you are free to opt for any of them. Here we are going to show you how to use a voltage regulator to step down the voltage from 9v to 5v or 3.3v

The most common and preferred voltage regulator is 7805, which is capable of regulating voltage supply out to 5v. This regulator is preferred because its cheap and easily available in local market, capable for high current sourcing i.e 1.5A, which is reasonably enough for most of the applications and circuit complexity is less, just some capacitors and you are ready to go. In addition to this vast Input voltage range(max upto 35v and 40v in some variant). The 78xx voltage regulator family comes in different configuration, so all you need to do is select you desired output voltage and buy the corresponding regulator, like 3.3v, 9v, 12v, etc.

Lets see the Pin configuration of the 7805 voltage regulator:

We will use this voltage regulator to build a standard 5v power supply for breadboard, so that you don’t have to worry about supply Input. Adding this power supply to your breadboard will give you the flexibility to use any of the battery source. We will recommend you to dedicate one corner section of the breadboard for the voltage regulator, so that you don’t have to plug-unplug it for every other applications. Now let us show you how to build a simple breadboard power supply, refer the below diagram for better idea.

The circuit shown above is really simple, we had used four capacitors in total which you can reduce to three also. Let me describe you the purpose of these capacitors, one by one:

1. 1000uF capacitor: If you look in the circuit, you can see one 1000uF polarized capacitor, the polarity matters to this capacitors, thus you need to take care of its polarity while connecting. Silver strip indicates the position of negative leg of the capacitor. The purpose of this capacitor is to store the charge before supplying anything to the voltage regulator, i.e it act as global reservoir, thus making it sure that supply to the voltage regulator from the battery source will always remains constant.
2. 10uF Capacitor: These are nothing but local reservoir which will store the charge before supplying to the circuits, thus making sure that there is always a constant power supply across all the parts. We used two 10uf polarized capacitors in the circuit because we want both the parallel outer tracks of the breadboard to be supplied with constant power. You can fit in just one capacitor next to 7805 Out pin.
3. 0.1uF Capacitor: we had used one ceramic capacitor in the output of 7805 voltage regulator, just to filter out any unwanted voltage spike(ripples) also called as noise, thus these tiny ceramic caps can act as filter element in the power supply you built. The polarity of these capacitors does not matters at all, you can use it either way.

Note: There are breaks in the outer tracks of breadboard, exact in the center portion, refer the diagram above, we had used wires as jumper to extend the power supply further, mentioned as power supply extension in the diagram.

The orange line shown in the image above is Input to voltage regulator, you can supply upto 35v to this wire to get a constant regulated 5v output voltage. If you supply high voltage to voltage regulator like 12v or 24v, you will see that voltage regulator getting hot, this is because of voltage regulator power dissipation in the form of heat to covert that much high voltage to 5 volt out. Don’t touch your fingers or hands to regulator in case its hots and if you feels that voltage regulator getting hot every time, then its better to use use Heat sink for voltage regulator.

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.