The Start

Hi, What and Why

Plug it in

Rule number 1

Water Sensor

Sound Sensor


Tri Colour LED

RTC (Real Time Clock) DS1302

RTC (Real Time Clock) DS3231

Matrix LED step 1


Stepper Motor

LCD revisited with PCF8574T

Humidity Sensor

Shift Register

RFID tags (RC-522)

7 Segment display

Ultrasonic distance sensor

5V regulator

analogRead and analogWrite

Wiring an Array of Switches

The next step

Other things I have bought

Infra red and Processing

Programming a separate arduino chip

Creating your own PCB

L293D for a DC motor

4 digit 7 segment display

Starting with motors

RF433 Wireless Comms

Sort a character array

More stuff

I2C devices (SDA,SCL)

I2C scanner

SPI devices (MOSI,MISO)

HMC5883L Compass

MMA7361 Accelerometer

Added projects

Message Display System

4WD robot car
4WD robot car II

4WD robot car COMPLETE

MP3 Player

Tinkering with a motor

Transistor pins and schematic layout. (Wikipedia) motors
Goal : motors
Wired up. motors
int T1 = 10;

void setup()
  pinMode(T1, OUTPUT);

void loop()
digitalWrite(T1, HIGH);
digitalWrite(T1, LOW);

With a resistor of 1K2 (1200) between base and arduino, and a voltmeter across the base and emitter:

part 1 - setting it LOW  = 0.45v - motor is ON
part 2 - setting it HIGH = 5.21v - motor is OFF
With a resistor of 100K (100,000) between base and arduino, and a voltmeter across the base and emitter:
part 1 - setting it LOW  = 5.45v - motor is OFF
part 2 - setting it HIGH = 5.59v - motor is OFF
So clearly the value of the resistor is critical. But why: with a bigger resistor, isn't the voltage always LOW ? Why is it always HIGH ?
V = I x R. 
5 = n x 1200; gives us 4.17 milliAmps mA
5 = n x 100,000; gives us 0.05 milliAmps mA

But that is with the battery plugged in as well - without the battery, the values return to normal :
Even with a 100K resistor, the value switches between 0V and 5V

Darlington pair. motors

The darlington pair failed at first, since I had 2 different transistor types. 2907 and 2222 I put 2 x 2222 transistors as a pair and it worked well. The motor seemed to be spinning faster ?

Darlington pair wired up. motors