2021 PROJECTS

In this post, I will cover some projects I have worked on over the last few months and some projects I have planned for the future.

Bipedal Robot


I am currently busy building a bipedal robot based on this Instructables post by K.Biagini. I used his design as a foundation and added additional components and functionality (such as arms and a Piezo for sound).

I had to modify his 3D models to achieve what I wanted. Here are links to download my modified 3d Models:
– Body Extension (to fit in the extra components) – Link
– Modified Head – Link
– Arms – Link

Here is a list of all the electronic components used:
– 1x Arduino Nano
– 6x micro servos
– 2 x push buttons
– 1x mini toggle switch
– 1x 9v Battery
– 1x ultrasonic sensor (HC-SR04)
– 1x RGB LED
– 1x Piezo

These components are connected as follows:

Pinout configuration of Arduino Nano:

Pin NumberConnected Hardware
2Ultrasonic Sensor Echo Pin
3RGB LED Red Pin
4Push Button 1
5RGB LED Green Pin
6RGB LED Blue Pin
7Push Button 2
8Servo Signal Pin (Right Hip)
9Servo Signal Pin (Right Ankle)
10Servo Signal Pin (Left Hip)
11Piezo
12Servo Signal Pin (Left Ankle)
13Ultrasonic Sensor Trigger Pin
14 (A0)Servo Signal Pin (Left Arm)
15 (A1)Servo Signal Pin (Right Arm)

This is still an in-progress project and is not done, Especially from a coding perspective on the Arduino, but once I have completed this project, I will create a post containing the complete source code.

Rotary Control

I needed a rotary control for another project discussed below, so I decided to build one as per this Post on the Prusa Printers blog. It is based on an Arduino Pro Micro and uses Rotary Encoder Module.

I modified the code available on the Prusa blog to mimic keyboard WASD inputs. Turning the dial left and right will input A and D, respectively. Pressing in the dial control push button will switch to up and down inputs, thus turning the dial left and right will input W and S.
Here is the modified code (Based on Prusa Printers blog post code):

#include <ClickEncoder.h>
#include <TimerOne.h>
#include <HID-Project.h>

#define ENCODER_CLK A0 
#define ENCODER_DT A1
#define ENCODER_SW A2

ClickEncoder *encoder; // variable representing the rotary encoder
int16_t last, value; // variables for current and last rotation value
bool upDown = false;
void timerIsr() {
  encoder->service();
}

void setup() {
  Serial.begin(9600); // Opens the serial connection
  Keyboard.begin();
  encoder = new ClickEncoder(ENCODER_DT, ENCODER_CLK, ENCODER_SW); 

  Timer1.initialize(1000); // Initializes the timer
  Timer1.attachInterrupt(timerIsr); 
  last = -1;
} 

void loop() {  
  value += encoder->getValue();

  if (value != last) { 
    if (upDown)
    {
    if(last<value) // Detecting the direction of rotation
        Keyboard.write('s');
      else
        Keyboard.write('w');
    }
    else
    {
      if(last<value) // Detecting the direction of rotation
        Keyboard.write('d');
      else
        Keyboard.write('a');
    }
    last = value; 
    Serial.print("Encoder Value: "); 
    Serial.println(value);
  }

  // This next part handles the rotary encoder BUTTON
  ClickEncoder::Button b = encoder->getButton(); 
  if (b != ClickEncoder::Open) {
    switch (b) {
      case ClickEncoder::Clicked: 
        upDown = !upDown;
      break;      
      
      case ClickEncoder::DoubleClicked: 
        
      break;      
    }
  }

  delay(10); 
}

I use the rotary control with a Raspberry Pi to control a camera pan-tilt mechanism. Here is a video showing it in action:

I will cover the purpose of the camera as well as the configuration and coding related to the pan-tilt mechanism later in this post.

Raspberry Pi Projects

Raspberry Pi and TensorFlow lite

TensorFlow is a deep learning library developed by Google that allows for the easy creation and implementation of Machine Learning models. There are many articles available online on how to do this, so I will not focus on how to do this.

At a high level, I created a basic object identification model created on my windows PC and then converted the model to a TensorFlow lite model that can be run on a Raspberry pi 4. When the TensorFlow lite model is run on the Raspberry Pi, a video feed is shown of the attached Raspberry Pi camera, with green blocks around items that the model has identified with a text label of what the model believes the object is, as well as a numerical percentage which indicates the level of confidence the model has in the object identification.

I have attached a 3inch LCD screen (in a 3D printed housing) to the Raspberry Pi to show the video feed and object identification in real-time.

The Raspberry Pi Camera is mounted on a pan-tilt bracket which is controlled via two micro servos. As mentioned earlier, the pan-tilt mechanism is controlled via the dial control discussed earlier. The pan-tilt mechanism servos are driven by an Arduino Uno R3 connected to the Raspberry Pi 4 via USB. I initially connected servos straight to Raspberry Pi GPIO pins. However, this resulted in servo jitter. After numerous modifications and attempted fixes, I was not happy with the results, so I decided to use an Arduino Uno R3 to drive the servos instead and connect it to the Raspberry Pi Via USB. I have always found hardware interfacing significantly easier with Arduino and also the result more consistent.

Here is a diagram of how the servos are connected to the Arduino Uno R3:

Below is the Arduino source code I wrote to control the servos. Instructions are sent to the Arduino through serial communication via USB, and the servos are adjusted accordingly.

#include <Servo.h>
#define SERVO1_PIN A2
#define SERVO2_PIN A3

Servo servo1;
Servo servo2;
String direction;
String key;
int servo1Pos = 0;
int servo2Pos = 0;

void setup()
{
  servo1Pos = 90;
  servo2Pos = 90;
  Serial.begin(9600);
  servo1.attach(SERVO1_PIN);
  servo2.attach(SERVO2_PIN);

  servo1.write(30);
  delay(500);
  servo1.write(180);
  delay(500);
  servo1.write(servo1Pos);
  delay(500);
  servo2.write(30);
  delay(500);
  servo2.write(150);
  delay(500);
  servo2.write(servo2Pos);
  delay(500);
  Serial.println("Started");
  servo1.detach();
  servo2.detach();
}

String readSerialPort()
{
  String msg = "";
  if (Serial.available()) {
    delay(10);
    msg = Serial.read();
    Serial.flush();
    msg.trim();
    Serial.println(msg);
  }
  return msg;
}

void loop()
{
  direction = "";
  direction = readSerialPort();
  //Serial.print("direction : " + direction);
  key = "";

  if (direction != "")
  {
    direction.trim();
    key = direction;

    servo1.attach(SERVO1_PIN);
    servo2.attach(SERVO2_PIN);

    if (key == "97")
    {
      if (servo2Pos > 30)
      {
        servo2Pos -= 10;
      }
      servo2.write(servo2Pos);
      delay(500);
      Serial.print("A");
    }

    else if (key == "115")
    {
      if (servo1Pos < 180)
      {
        servo1Pos += 10;
      }
      servo1.write(servo1Pos);
      delay(500);
      Serial.print("S");
    }

    else if (key == "119")
    {
      if (servo1Pos > 30)
      {
        servo1Pos -= 10;
      }
      servo1.write(servo1Pos);
      delay(500);
      Serial.print("W");
    }

    else if (key == "100")
    {
      if (servo2Pos < 150)
      {
        servo2Pos += 10;
      }
      servo2.write(servo2Pos);
      delay(500);
      Serial.print("D");
    }

    delay(100);
    servo1.detach();
    servo2.detach();
  }

}

On the Raspberry Pi, the following Python script is used to transfer the rotary control input via serial communication to the Arduino:

# Import libraries
import serial
import time
import keyboard
import pygame

pygame.init()
screen = pygame.display.set_mode((1, 1))

with serial.Serial("/dev/ttyACM0", 9600, timeout=1) as arduino:
    time.sleep(0.1)
if arduino.isOpen():
    done = False
while not done:
    for event in pygame.event.get():
    if event.type == pygame.QUIT:
    done = True
elif event.type == pygame.KEYDOWN:
if event.key == pygame.K_s:
    arduino.write('s'.encode())

if event.key == pygame.K_w:
    arduino.write('w'.encode())

if event.key == pygame.K_a:
    arduino.write('a'.encode())

if event.key == pygame.K_d:
    arduino.write('d'.encode())
time.sleep(0.5)

arduino.Close();
print ("Goodbye")

The next thing I want to implement on this project is face tracking using TensorFlow lite with automated camera movement.

Raspberry Pi Zero W Mini PC

I built a tiny PC using a Raspberry Pi Zero W combined with a RII RT-MWK01 V3 wireless mini keyboard and a 5 inch LCD display for Raspberry Pi with a 3D printed screen stand.


It is possible to run Quake 1 on the Raspberry Pi Zero following the instructions in this GitHub, and it runs great.

Raspberry Pi Mini Server Rack

I have 3D printed a mini server rack and configured a four Raspberry Pi Cluster consisting of three raspberry Pi 3s and one Raspberry Pi 2. They are all networked via a basic five-port switch.

I am currently busy with a few different projects using the Pi cluster and will have some posts in the future going into some more details on these projects.

I developed a little Python application to monitor my different Raspberry Pis and show which ones are online (shown in green) and offline (shown in red).

The application pings each endpoint every 5 seconds, and it is also possible to click on an individual endpoint to ping it immediately. The list of endpoints is read from a CSV file, and it is easy to add additional endpoints. The UI is automatically updated on program startup with the endpoints listed in the CSV file.

Here is the Python source code of the application:

import PySimpleGUI as sg
import csv
import time
import os
from apscheduler.schedulers.background import BackgroundScheduler


def ping(address):
    response = os.system("ping -n 1 " + address)
    return response


def update_element(server):
    global window
    global layout
    response = ping(server.address)
    if response == 0:
        server.status = 1
        window.Element(server.name).Update(button_color=('white', 'green'))
        window.refresh()
    else:
        server.status = 0
        window.Element(server.name).Update(button_color=('white', 'red'))
        window.refresh()


def update_window():
    global serverList
    for server in serverlist:
        update_element(server)


class server:
    def __init__(self, name, address, status):
        self.name = name
        self.address = address
        self.status = status


serverlist = []

with open('servers.csv') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')
    line_count = 0
    for row in csv_reader:
        if line_count == 0:
            line_count += 1
        else:
            serverlist.append(server(row[0], row[1], 0))
            line_count += 1

layout = [
    [sg.Text("Server List:")],
]

for server in serverlist:
    layout.append([sg.Button('%s' % server.name, 
                    button_color=('white', 'orange'), 
                    key='%s' % server.name)])

window = sg.Window(title="KillerRobotics Server Monitor", 
                    layout=layout, margins=(100, 30))
window.finalize()
scheduler = BackgroundScheduler()
scheduler.start()

scheduler.add_job(update_window, 'interval', seconds=5, id='server_check_job')

while True:
    event, values = window.read()
    if event == sg.WIN_CLOSED:
        scheduler.remove_all_jobs()
        scheduler.shutdown()
        window.close()
        break
    elif event in [server.name for server in serverlist]:
        scheduler.pause()
        update_element([server for server in 
                         serverlist if server.name == event][0])
        scheduler.resume()

Raspberry Pi Pico

I ordered a few Raspberry Pi Picos on its release, and thus far, I am very impressed with this small and inexpensive microcontroller.

The Raspberry Pi Pico sells for $4 (USD) and has the following specifications:
– RP2040 microcontroller chip designed by Raspberry Pi
– Dual-core Arm Cortex-M0+ processor, flexible clock running up to 133 MHz
– 264KB on-chip SRAM
– 2MB on-board QSPI Flash
– 26 multifunction GPIO pins, including 3 analogue inputs
– 2 × UART, 2 × SPI controllers, 2 × I2C controllers, 16 × PWM channels
– 1 × USB 1.1 controller and PHY, with host and device support
– 8 × Programmable I/O (PIO) state machines for custom peripheral support
– Low-power sleep and dormant modes
– Accurate on-chip clock
– Temperature sensor
– Accelerated integer and floating-point libraries on-chip

It is a versatile little microcontroller that nicely fills the gap between Arduino and similar microcontrollers and the more traditional Raspberry Pis or similar single board computers.
I have only scratched the surface of using the Pico on some really basic projects, but I have quite a few ideas of using it on some more interesting projects in the future.

3D Printing

I ran into some problems with my 3D printer (Wanhao i3 Mini) over the last few months. The First problem was that half of the printed LCD display died, which was an annoyance, but the printer was still usable. The next issue, which was significantly more severe, was that the printer was unable to heat up the hot end.

My first course of action was to replace both the heating cartridge and the thermistor to ensure that neither of those components were to blame, and unfortunately, they were not. After some diagnostics with a multimeter on the printer’s motherboard, I determined that no power was passing through to the heating cartridge connectors on the motherboard.

I ordered a replacement motherboard and installed it, and the 3D printer is working as good as new again. When I have some more time, I will try and diagnose the exact problem on the old motherboard and repair it.
Here are photos of the old motherboard I removed from the printer:

Below are some photos of a few things I have 3D printed the last few months:

2021 PROJECTS

A Tour of Silicon Valley

I recently did a self-tour of Silicon Valley, and as someone who works in the field of technology, it was a fantastic experience.

The first stop of the tour was Apple Park, the Head Quarters for Apple Inc. The only section open to the public is the Visitor Center, which mainly consists of a massive apple store (which was insanely busy as it was 2 days after the iPhone 11 and 11 Pro launched) as well as a sizeable Augmented Reality display of the Apple Park Campus and the famous UFO looking Apple Ring building. This AR display consists of a large model, shown in the photos below, that you can interact with using an iPad Pro which the staff hand out to guests entering the display area. On the iPad Pro graphics are superimposed over the model showing not only a realistic aerial view of the campus but also showing various bits of information relating to the design of the ring building such as how the ring building is designed in a way to take advantage of the environment (wind, etc.) to cool itself in an ecologically friendly manner.

The next stop was the Apple Garage, which is the garage at the house in which Steve Jobs grew up. It is commonly considered the birthplace of Apple. Steve Wozniak (Apple co-founder) has said that this is a bit of a romanticized myth, but it was still great to see.

IMG_9460

Next came the Computer History Museum, a truly amazing museum with items covering the entire history of computers. From the abacus to mainframes and supercomputers to the current day smartphone, the items on display are truly astonishing. Below are some photos and descriptions of some of the items on display.

Numerous Abacuses on display, one of the oldest forms of calculation tools.

A variety of mechanical calculation machines.

IMG_9482

A Curta Calculator, also known as the Pepper Grinder Calculator. One of the most advanced handheld mechanical calculators ever created.

A Selection of IBM Mainframe Equipment.

IMG_9510

A model of ENIAC, the world’s first general-purpose computer.

IMG_9536

A Selection of Fortran Programming Books and Promotional Material.

A PDP-1 Display, Spacewar! one of the first video games ever was programmed on and ran on the PDP-1.

IMG_9551

A 486 DX motherboard.

A display showing the advancement of transistors, microprocessors, silicon wafers, and Moore’s Law.

Various Robots on display. Including expensive toys, industrial robots, and research robots.

Numerous bizarre and unusual computer peripherals on display.

Video and computer gaming displays, with various consoles and games on display.

Apple I, Apple II, Apple Lisa, and Original Macintosh computers.

IBM PC Model 5150 and an Altair 8800.

IMG_9663

A boxed copy of Windows 1.0.

IMG_9667

The NeXTcube workstation from NeXt Computers. NeXt computers were founded by Steve Jobs after leaving Apple in 1985, and Next Computers were acquired by Apple when Steve Jobs rejoined Apple in 1997. The NeXTStep Operating system became the foundation for Mac OSX.

IMG_9671

Waymo Self-Driving Car.

IMG_9673

A scale model of the Mars Rover.

World of Warcraft exhibition.

An exhibition showing the rise of MP3s and the rise and fall of Napster.

The next stop after the Computer History Museum was the Googleplex, the massive headquarters of Google. The Googleplex, which is mostly open to the public, has various significant things to see, such as the Android Statue Lawn, where retired Android statues representing previous versions of the mobile operating system are on display. From volleyball courts to Massive Statues to vegetable gardens, it is easy to see why the Google Campus has a reputation as the best working environment. Here are a few photos of the Googleplex.

The last stop in Silicon Valley was Stanford University, a University that amongst its alumni has various famous people. Stanford has a beautiful Campus, as can be seen in the photos below.

A Tour of Silicon Valley

UCTRONICS SMART ROBOT CAR KIT

uctronrobot

The UCTRONICS Smart Robot Car Kit is an easy to build obstacle avoidance robot kit that also allows for direct user control of the robot through either Infrared (using the included remote control) or Bluetooth (an Android App is available on the Google Play Store).

This is a great starter kit as no soldering is required and additionally there is a lot of space on the robot chassis for customization and additions later on. Assembly instructions are provided in full color and takes the builder through the assembly process in a step-by-step manner, which is easy to follow.
A prebuilt Arduino sketch is available for download from the UCTRONICS website to make the assembled robot functional, however nothing prevents the builder from writing their own. This is however one area where I do feel the kit falls short as an educational tool, instead of just providing a prebuilt sketch, it would have been great if a step-by-step guide was provided taking the builder through the process of writing their own sketch, explaining concepts and what is being done and why along the way.
This is however still a great starter kit and I would recommend it for anyone getting started in robotics or Arduino related building.

UCTRONICS SMART ROBOT CAR KIT

DIY VR Headset for $80 (DIY VR Part 2)

IMG_1817

The purpose of this series of posts was to look at ways to experience VR at home for the lowest cost possible. In Part 1 of DIY VR, we took a look at using a smart phone and a Google cardboard compatible headset to stream computer games to the phone in stereoscopic 3D. The main problem with this approach was that it was still relatively expensive as it required a smart phone (iOS or Android) to function.

Now in part 2 we will look at building a VR headset from scratch. My initial goal was to do this for under $150(USD), however after shopping around and changing some parts out for alternatives I managed to get this down to around $80. So let us get started.

The parts required are:

  • Toggle Flick Switch
  • 2x LED
  • 1x resistor 150 Ohm
  • 1x Micro USB cable (at least 2 meters long)
  • 1x HDMI Cable (thin ones work best as they hinder movement less, also at least 2 meters long)
  • Some jumper wires
  • DC Adapter plug 5V 3A (Raspberry Pi compatible one works great)
  • Push Button
  • Google Cardboard Compatible VR Headset (I recommend one with a phone compartment door that opens as it gives better access than the ones which uses a tray that slides in)
  • 6DOF MPU 6050 3Axis gyroscope and accelerometer
  • Arduino Micro (can use off brand alternative)
  • 5inch RaspberryPi LCD Screen 800×480 with HDMI interface

All of these parts can be acquired on AliExpress for about $80 ($82.78 to be precise), as shown in the image below:

Resistorflick_switchwireDC AdapmicroUSBHeadsetpushbuttonledMPU6050lcdHDMIarduinoMicrototals

You will also require Tridef3D or similar software (there are some free alternatives, but I have not had a chance to give them a try at present). Tridef3D is used to convert any Direct X 9/10/11 game into stereoscopic 3D. Tridef3D offers a 14-day free trial, which is plenty to give this a try. The full version of Tridef3D retails for $39.99.

Now that we have all the required components, let us begin with the assembly.

The assembly comprises of 3 main elements:

  1. The Arduino Micro circuit (containing the MPU 6050, push button and led)
  2. The Wiring (providing connectivity to Arduino Micro and power to Screen)
  3. Inserting the screen in the headset and connecting the micro USB cables as well as the HDMI cable.

The Arduino Micro circuit

The diagram below illustrates how the different components need to be connected to the Arduino Micro:

vr_bb1

The push button uses digital pin 5 and the MPU 6050 is connected to the Arduino Micro as follows:

– MPU 6050 SCL pin to Digital Pin 3 on Arduino

– MPU 6050 SDA pin to Digital Pin 2 on Arduino

– MPU 6050 VCC to 5V pin on Arduino

– MPU 6050 GND to GND pin on Arduino

The code to be loaded on the Arduino is as follows:

#include <Mouse.h>
#include <Wire.h>
#include <I2Cdev.h>
#include <MPU6050.h>

MPU6050 mpu;
int16_t ax, ay, az, gx, gy, gz;
int vx, vy;
int inputPin = 5;
bool enableMouse;

void setup() {
Serial.begin(9600);
Wire.begin();
mpu.initialize();
enableMouse = true;
pinMode(inputPin, INPUT);
if (!mpu.testConnection()) {
while (1);
}
Serial.println("Running...");
}

void loop() {
int val = digitalRead(inputPin);
if (val == HIGH) { // check if the input is HIGH
//Place logic here to execute when button is pressed
//Disables mouse movement while button is pressed, this allows you to set your view angle easily.
enableMouse = false;
}
else
{
enableMouse = true;
}
if(enableMouse)
{
mpu.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
vx = -(gy)/150;
vy = (gz+100)/150;
Mouse.move(vx, vy);
delay(20);
}
}

Just note that the orientation of the MPU 6050 makes a difference to which of the axis of the gyroscope will be used. For the above code the MPU 6050 was mounted on the side of the headset as shown in the pictures below:

IMG_1795

In the event of the MPU 6050 being mounted with a different orientation you might have to substitute between the gx, gy and gz values until the desired configuration is achieved.

For my configuration I am rotating around the Y and Z axis.

Also the numbers associated with calculation of vx and vy might have to be tweaked to get the results (movement speed etc.) you desire.

I also added a push button, that when pressed temporarily disables the gyroscopic mouse movement. This is useful when you want to reset you point of view in games.

I attached all the parts of this circuit to the VR Headset using double-sided tape.

The Wiring

In order to have as few cables as possible connecting to the VR headset I modified the USB cable so that it pulls external power from a DC power adapter (a single USB port will not be able to power both the Arduino and the 5 inch LCD) as well as splitting into 2 micro USBs on one end (one only provided power to the LCD and the other one both power and connectivity to Arduino.) the below diagram shows how the wiring is connected:

VR2_bb

For reference a USB cables contains 4 wires:

  • Red wire – +5V DC
  • White or Yellow – Data connectivity
  • Green – Data Connectivity
  • Black – GND

I also included a switch to turn the power on and off (this is useful to turn off the mouse functionality until it is needed, otherwise it will interfere with mouse movement when it is not desired) as well as an LED to show when the headset is powered on.

IMG_1807

Inserting Screen in Headset and connecting all the wiring

The LCD screen is held in place by the clamps in the headset used to hold a phone (it is a snug fit). Then simply connect the 2 micro USBs to the LCD and Arduino respectively (ensuring the plug with the data connections is plugged into the Arduino and that the power only micro USB is plugged into the power socket on the LCD display). Try to run the cables in the extra spaces in the Headset around the screen in order to keep them out of the way.

Lastly connect the HDMI cable to the LCD.

The assembly is now complete.

IMG_1817

Connecting headset to PC and setting up software

To connect the headset to your PC do the following:

  1. Plug the DC adapter into mains power.
  2. Plug the USB connector into an available USB port in your PC.
  3. Connect HDMI cable into and available HDMI port on your PC graphics card (You can use a DVI port with an adapter)

Go to display settings and click on detect displays, then set Multiple displays to “Duplicate these Displays” and make sure your resolution is set to 800×480.

Open up Tridef3D and start-up a game.

You might have to play around with each individual games graphical settings as well as mouse sensitivity to get the best results.

For future enhancements I will look at getting a higher definition LCD screen and also work on head movement tracking by using infrared LEDs and a Wiimote (Wiimote used as a IR Camera).

And there you have it a DIY VR Headset for $80. Give it a try.

Here is a short demonstration video:

DIY VR Headset for $80 (DIY VR Part 2)

Diodes

diode

Today we will look at the last component in our 3 part series on basic electronic components, the diode.

Diodes only allows electricity to flow through them in a single direction, this is achieved by the diode having a low resistance, ideally zero, in one direction and a high resistance, ideally infinite, in the other direction. This does mean that diodes are polarized (they have 2 terminal, an anode and a cathode) and the direction in which they are placed in a circuit is of great importance.

Diodes are extremely important in converting AC to DC though their use in a bridge-rectifier, but that is a topic for another post.

Diodes usually have 2 markings on them, a band to indicate the side of the cathode and secondly the diode type code (for example 1N4148) this can be used to look up the maximum voltage and current the diode allows.

Here is the schematic symbol used to represent a diode:

diodesymbol

Diodes

Capacitors

Today we will cover the next in our series of the basic electronic component, the capacitor.

caps

A capacitor is used to store and release electrical charge in a circuit. When the voltage in the circuit is higher than what is stored in the capacitor, the capacitor will allow current to flow in and the capacitor will be given a charge. When the voltage in the circuit drops lower than what is stored in the capacitor it will dis-charge, releasing its stored charge into the circuit. This will cause the voltage in the circuit to temporarily raise.

This is extremely useful as some components, such as electric motors, use more power when they are first activated then when they are already active which can cause a voltage drop in the circuit that can have negative effects on other components in the circuit.

Capacitors help level out these fluctuations in voltage.

There are 2 main types of capacitors, Polarized and Non-Polarized. I will not go into a great deal of detail regarding the differences, but in a nut shell non-polarized capacitors have no implicit polarity and can thus be connected to the circuit either way, whereas polarized capacitors have a defined + and – terminal and must be connected to the circuit corresponding to its terminal polarity. This also means that non-polarized capacitors are suited for use with AC, but polarized capacitors are strictly only suited for DC as they experience large leakage if the voltage is inverted across its terminals as is the case with AC, which can cause the capacitor to overheat.

The capacitance of a capacitor is measured in Farad(F). For most circuits you will likely work on microFarad(µF) and picoFarad(pF) sized capacitors will be utilised.

Here are the schematics used to represent both polarized and non-polarized capacitors:

Polarized Capacitor

polarized cap            Non-Polarized Capacitornon polarized cap

Capacitors

Resistors

In a previous post we had a look at transistors, in the next few posts we will look at 3 other basic electronic components; resistors, capacitors and diodes.

Let us start with the most basic of the 3 today, the resistor. As their name suggest, they resist the flow of electrical current through a circuit. The change in current can be determined using Ohm’s Law, which states that the current flowing through a conductor equals the Voltage across the conductor divided by the resistance present in the conductor, or  I = V/R, where I represents current (measured in Amps), V represents Voltage (measured in Volts) and R represents the resistance (measured in Ohms Ω).

Resistors have coloured stripes along their sides which are used to indicate their values, here is the table used for value lookup:

Colour Value
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Grey 8
White 9

A simple way to remember the sequence of the colours is with the rhyme:
Better Be Right Or Your Great Big Venture Goes Wrong.

The last stripe indicates the tolerance of the resistor:

Colour Value
Brown ±1%
Red ±2%
Gold ±5%
Silver ±10%

Here is an example of how to utilise the table:

resistor 220

The resistor above has 3 colour stripes and a tolerance stripe.

Red Red Brown with a Gold tolerance stripe.

This translates to:

2 2 x 10¹ ± 5% = 220Ω ±5%

Now for an example with a Resistor with 5 stripes:

resistor 10k

The resistor above has 4 colour stripes and a tolerance stripe.

Brown Black Black Red and a Gold tolerance stripe.

This Translates to:

1 0 0 x 10²± 5% = 10,000Ω ±5% = 10kΩ ±5%

Here is the schematic used to represent Resistors in a circuit diagram:

Resistor Symbol

Resistors

Elecfreaks Arduino Advanced Kit

Box2

The Elecfreaks Arduino Advanced Kit is an AWSOME product. It contains everything you need to build some impressive Arduino based projects, including a MP3 player, an Alcohol tester and a Tetris game to name a few.

The Kit includes:

  • 1 x Freaduino UNO    
  • 1 x mini USB cable
  • 1 x TFT1.8 LCD 
  • 1 x Octopus ADKey     
  • 1 x Octopus Passive Buzzer Brick    
  • 1 x Octopus MQ3 Gas Sensor Brick     
  • 1 x MP3 Module     
  • 1 x Color Sensor     
  • 1 x 9 DOF Module
  • 1 x ESP8266 Serial Wi-Fi Module
  • 1 x BLE Adapter 
  • 1 x One Channel Relay Brick 
  • 1 x Octopus 5mm LED Brick
  • 1 x 9V AA Battery Holder
  • 30 x Jumper wires

The Kit comes with an Arduino compatible Freaduino board, which is simply an Arduino UNO R3 manufactured by Elecfreaks.

All the components come individually packed in small boxes (all of which are clearly labeled) and it is really well presented.

The kit also includes color printed cards illustrating each project and how to assemble it. Additionally the kit has a wiki page (http://www.elecfreaks.com/wiki/index.php?title=Arduino_Advanced_Kit_-_EN), which contains the source code for all the projects.

The Elecfreaks Arduino Advanced Kit is great value as it is less expensive than buying all the individual components separately (and also a great deal more convenient).

I highly recommend this kit to anyone interested in developing/building in the Arduino space.  

Elecfreaks Arduino Advanced Kit

IoT

I am starting an IoT project and wanted to share a little bit.  IoT or the Internet of Things is defined on Wikipedia as “the network of physical objects—devices, vehicles, buildings and other items embedded with electronics, software, sensors and network connectivity—that enables these objects to collect and exchange data. The Internet of Things allows objects to be sensed and controlled remotely across existing network infrastructure, creating opportunities for more direct integration of the physical world into computer-based systems, and resulting in improved efficiency, accuracy and economic benefit;”.  

To learn more I would recommend the book The Internet of Things Do-It-Yourself at Home Projects for Arduino, Raspberry Pi, and BeagleBone Black by Donald Norris. It provides an in-depth technical overview of concepts as well as some projects that can be built. The projects in the book are not particularly exciting but they do a good job at illustrating concepts and methods utilised.

Book

So I am going to be using a Raspberry Pi2 running Windows 10 IoT core, which will be communicating with some Arduino boards.

I am also looking at integrating with Azure Machine Learning to do some interesting things. 

I have not decided on many elements of the final project, but it will involve a robot.

rasp

On a side note, do not try to deploy Windows 10 IoT Core on a SD card using a Mac, it is a huge pain. My main computer I use at home (and for most of my development, blogging, video editing, etc.) is a MacBook Pro and in the end I gave up trying to get the deploy working and used my windows laptop which worked almost instantaneously.

Once I have decided exactly what I want to achieve and made some progress I will post more on this topic.

IoT

BITE SIZE ARDUINO – PIEZO BUZZER

Today we will have a look at how to connect a piezo buzzer to an Arduino and how to generate different audio signals with it. A piezo buzzer is a audio signalling device, it is the most basic electronic component by which to generate sounds at different frequencies.

A piezo buzzer has 2 connection terminals, one is connected to GND and the other to a PWM digital pin, for this example we will use pin 3.

piezo_bb

We will use the tone() function to generate tones at different frequencies, for an Arduino Uno the frequency rage is between 31 and 65535 Hz. Please note that the possible min and max frequencies differ between different models of Arduino boards. The tone() function takes 3 parameters, firstly the pin to use, then the frequency to use and lastly the duration to generate the tone in milliseconds.

Here is the code used:

#define PIEZO_PIN 3

void setup()
{
}

void loop()
{
     tone(PIEZO_PIN, 31, 1000);
     delay(500); // Pause between Tones 
     tone(PIEZO_PIN, 15000, 1000);
     delay(500); // Pause between Tones 
     tone(PIEZO_PIN, 30000, 1000);
     delay(500); // Pause between Tones 
     tone(PIEZO_PIN, 45000, 1000);
     delay(500); // Pause between Tones 
     tone(PIEZO_PIN, 65535, 1000);
     delay(500); // Pause between Tones 
     noTone(PIEZO_PIN); // Silence Tones
     delay(500);
}
BITE SIZE ARDUINO – PIEZO BUZZER