Lie detector is one of those things that intrigues us all. Everyone would love to have it. But how can we get it? We can buy the polygraph on eBay of course, but it is damn expensive. Yeah, there are a few low cost toys, but i don’t think they work too well. It’s not worth of risk and you will throw your 30 bucks if choose to buy them. So what is the best solution? Build it!  With Arduino board of course. Arduino made it pretty simple. Click the little link called “read more” below and create your own lie detector.

Our polygraph will be based on galvanic skin response effect. When a person becomes nervous (and when a person lies, he becomes nervous) his skin resistance becomes smaller. Then our device will measure persons resistance. We will show when person is telling the truth or lies with RGB LED and buzzer. Lets build our Arduino project.

We will need this components:
One Arduino Diecimila or Duemilanove board or clone
Five R1-3 100 ohm 0.5W resistors
fourteen R4 470 K ohms 0.5W resistors
seventeen R5 100 K ohms variable resistors
one D1 RGB LED common anode
one S1 Piezotransducer sixty seven (without driver electronics)

Piezobuzzer should not be the type that don’t have electronic oscilator, it shod be just piezoelectric transducer. This is because we will generate frequency directly from Arduino board. We will measure person’s resistance by using person as one resistor in potential divider and real resistor as the other.

Here is the Arduino project  schematics:

The software part For Arduino is not complicated. We just need to compare voltage at A0 and A1 places. If the values are the same, then LED should be green. When A0 is much higher then A1, skin resistant fell and diode will be red and Arduino will start the buzzer. If A1 is higher then A0, diode will be blue.

Here is the program:

int red_Pin = 9;
int green_Pin = 10;
int blue_Pin = 11;
int buzzer_Pin = 7;
int pot_Pin = 1;
int sensor_Pin = 0;
long red = 0xFF0000;
long green = 0x00FF00;
long blue = 0×000080;
int band = 10;

void setup()
{
pinMode(pot_Pin, INPUT);
pinMode(sensor_Pin, INPUT);
pinMode(red_Pin, OUTPUT);
pinMode(green_Pin, OUTPUT);
pinMode(blue_Pin, OUTPUT);
pinMode(buzzer_Pin, OUTPUT);
}

void loop()
{
int gsr = analogRead(sensor_Pin);
int pot = analogRead(pot_Pin);
if (gsr > pot + band)
{
setColor(red);
beep();
}
else if (gsr < pot – band)
{
setColor(blue);
}
else
{
setColor(green);
}
}
void setColor(long rgb)
{
int red = rgb >> 16;
int green = (rgb >> 8) & 0xFF;
int blue = rgb & 0xFF;
analogWrite(red_Pin, 255 – red);
analogWrite(green_Pin, 255 – green);
analogWrite(blue_Pin, 255 – blue);
}
void beep()
{
// 5 Khz for 0.2 second
for (int i = 0; i < 1000; i++)
{
digitalWrite(buzzer_Pin, HIGH);
delayMicroseconds(100);
digitalWrite(buzzer_Pin, LOW);
delayMicroseconds(100);
}
}

When you finish programming, import your program and Your Arduino lie detector is ready. You will need someone willing to test the Arduino project. Just ask him is the sky green or something like that. You will see that it works. Have fun.

The post Arduino project – How to build a lie detector? appeared first on Robot kits and electronic components news and reviews..

There are three ways to control Kuratas  – 1.  through a remote  controller, a master slave type (you can actually enter in the robot and control it from inside. It has two joysticks and moving them you move the robot.), or an iPhone. Kurats has  an operating system V-Sido and it is equipped with a launcher and a two Gatling gun. You only need to smile if you want to activate the guns which by the way fire 6000 bullets in one minute. The robot is equipped with a Xbox Kinect in order to recognize your peoples  facial expressions.

Best part is that the Company allow customization of the robots. If you decide to buy it, you can equip the bot with all sorts of gadgets and upgrades. You can add glass holder, different sorts of guns, Shotproof, Pilotless Head and many other things. You can eve pick a color of your robot. Imagine your mean war machine in pink

This is like a dream robot for all robot kit fans. But there is one tiny problem. The price. The basic Kuratas costs 1.35 million dollars and upgrades make the price even bigger. If you have that kind of money, we suggest you buy this robot because we think it is worth every cent. And when you buy it, we’d like to ride with you a few miles

https://www.youtube.com/watch?v=hDQdgttKrSE

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For this project, we wil need a few things. First we will need Arduino board or some clone (that is why is called Arduino project ). We will also need red 5mm LED, green 5mm LED, two 270ohm 0.5W metal film resistor and 0.1 inch header strip and keypad. We will create this project on breadboard so we’ll need that as well.

All these electronic components you can find at electronickits.com, or your local electronic parts dealer.

If you understand how the keypad works, you won’t have the problem creating the schematics by yourself. Keypads are usually arranged in a grid so when we press one of the keys, it connects a row and column. The switches are placed at the intersection of row and column wires. With this system, we only need to use 7 digital pins instead of twelve (1 for each key).

Because of this keypad system, we will have a bit more work on coding. Don’t worry, we will show you the codeing part, you can even download some library from the person who created operating keypad for Arduino.

here is the code:

#include <Keypad.h>
char* secretCode = “1234″;
int position = 0;
const byte rows = 4;
const byte cols = 3;
char keys[rows][cols] = {
{’1′,’2′,’3′},
{’4′,’5′,’6′},
{’7′,’8′,’9′},
{‘*’,’0′,’#'}
};
byte rowPins[rows] = {2, 7, 6, 4};
byte colPins[cols] = {3, 1, 5};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, rows, cols);
int redPin = 9;
int greenPin = 8;
void setup()
{
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
setLocked(true);
}
void loop()
{
char key = keypad.getKey();
if (key == ‘*’ || key == ‘#’)
{
position = 0;
setLocked(true);
}
if (key == secretCode[position])
{
position ++;
}
if (position == 4)
{
setLocked(false);
}
delay(100);
}
void setLocked(int locked);

{
if (locked)
{
digitalWrite(redPin, HIGH);
digitalWrite(greenPin, LOW);
}
else
{
digitalWrite(redPin, LOW);
digitalWrite(greenPin, HIGH);
}
}

This code is not very complicated. The loop checks which key is pressed. If we press # or *, loop will set the variable to zero. If we press any other key (any of the numbers), it will check did we pressed expected key and move the loop to the next one. Program will operate that way for all chars. If the code is right, Arduino will turn on the green LED, and if not, red LED will be on.

We did not mention, in the beginning of the program you define your secret code which Arduino compares to the one you enter when testing the project. And we finished another Arduino project. Thanks for staying with us!

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Battery charger always come handy. Imagine the situation where you are on the road trip and you are taking photos with your handy camera that goes on 6V battery. On the half way your battery is dead and you need to recharge it in order to continue taking shots. In this electronic project we will help you to build your own car battery charger. Yes, you can buy some commercial solution, but where is fun in that? And this battery charger is cheaper than the one in the store. All parts for the charger can be found in local electronic store, but you can find it cheaper in online electronic stores. We recommend electronickits.com because they have quality electronic components and they are not expensive.

This  car charger can charge two types of batteries. Ordinary  12V and 6V batteries. If it is used a with transformer that can provide 4 to 5 A at a voltage between 12.6V and 16V then the 6V and 12v batteries will charge regardless the position of the switch on schematics. In fact we don’t need the switch at all.

Here is a battery charger circuit scheme:

We created this device so that battery charging current is limited to 4.2A. If we give a 600mV voltage on R1 resistor, then the T1 transistor starts to operate (conduct). T3 transistor help us to stop the charging the battery. Too much charging is avoided because the value of current on T3 is restricted. The distinction between applied voltage at T4′s collector and real voltage of the battery is balanced thru T4′s emitter junction.

The power input of T4 transistor can be calculated by multiplying load current and voltage difference we mentioned above. For 6V battery, charging power reaches 40W. After that device stops charging the battery. The rectifier diodes must provide 4A at 40V. One other thing, we must cool the T4 transistor. Heatsink must be placed on the transistor in order to cool it down.

Best way to build this electronic project is to build it on breadboard and with some good wires. Main concern is to dissipate the heat and to protect the circuit from temperature and damaging. To do that it must be placed in some kind of case. And then you have cool and cheap car battery charger. You just need to buy rechargeable batteries.

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For this project we will just improve our first one which we posted a few weeks ago. We created S.O.S. Morse code flashlight. Today we will create a device that can Translate characters into Morse code. It will get series of sentences as an input, and it will provide series of dots and lines (coded signals) on output.

For this device, you will need the same parts as for our first project.

One Arduino board or clone
23 D1 5-mm Red LEDs
6 R1 270 Ω 0.5W resistors

The scheme is the same as is in project 1.

For the software part, first you will have to know Morse code. You can find it anywhere on the net. We provided the one from Wikipedia. There are a few rules we must follow. Dash must be three times long as dot. Time between the dashes or dots is equal to the time of dot and the space between words is seven times longer the time between characters.

Here is how to program your arduino board:

int ledPin = 12;
char* letters[] = {“.-”, “-…”, “-.-.”, “-..”, “.”, “..-.”, “–.”, “….”, “..”,”.—”, “-.-”, “.-..”, “–”, “-.”, “—”, “.–.”, “–.-”, “.-.”, “…”, “-”, “..-”, “…-”, “.–”, “-..-”, “-.–”, “–..” };
char* numbers[] = {“—–”, “.—-”, “..—”, “…–”, “….-”, “…..”, “-….”, “–…”, “—..”, “—-.”};
int dotDelay = 200;
void setup()
{ pinMode(ledPin, OUTPUT);
Serial.begin(9600); }
void loop()
{ char ch; if (Serial.available())

{
ch = Serial.read(); // read a single letter
if (ch >= ‘a’ && ch <= ‘z’)
{
flashSequence(letters[ch - 'a']);
}
else if (ch >= ‘A’ && ch <= ‘Z’)
{
flashSequence(letters[ch - 'A']);
}
else if (ch >= ’0′ && ch <= ’9′)
{
flashSequence(numbers[ch - '0']);
}
else if (ch == ‘ ‘)
{
delay(dotDelay * 4);
}
}
}
void flashSequence(char* sequence)
{
int i = 0;
while (sequence[i] != NULL)
{
flashDotOrDash(sequence[i]);
i++;
}
delay(dotDelay * 3);
}
void flashDotOrDash(char dotOrDash)
{
digitalWrite(ledPin, HIGH);
if (dotOrDash == ‘.’)
{
delay(dotDelay);
}
else // must be a -
{
delay(dotDelay * 3);
}
digitalWrite(ledPin, LOW);
delay(dotDelay);
}

We must add the command:

Serial.begin(9600);

This command will se  the speed of USB port on our Arduino. This speed will be enough for our morse code. Also we will need to use tool in Arduino software called Serial Monitor. It will allow us to type messages which will be sent to Arduino for coding. You can start the tool by clicking icon on right side of your software. Then write something in the text box and press return key. Your device will start to blink that sentence in Morse code and your  Arduino project is finished!

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