How to count time in Arduino

There are two simple ways to do pretty exact time counting in Arduino. The first one is to use delay(). Everytime it runs a delay(1), it's 1 millisecond passed. (1millisecond =0.001second, which means to delay 1 second you need to run delay(1000). ) Like this, you can count the runnning time by counting the delayed milliseconds.

But you may have many defferent delay() in your loop codes and you don't know how many milliseconds have been delayed anymore because it runs everytime differently. In this case you will need to use millis(). It's an internal clock in Arduino which starts to count time everytime the Arduino board starts running or is reseted. It can be counted to 50 days. To give the data of millis() to a variable you have to define this variable as unsigned long.

Code Example

unsigned long Val;
void setup(){
  Serial.begin(9600);
}
void loop(){
  Val = millis();
  Serial.print("Count = "); Serial.println(Val);
  delay(1000);
}

Reference:
http://arduino.cc/en/Reference/Millis

How to use AREF of Arduino

The aref works like this...

When you do analogue to digital conversion the arduino board uses the 5V supply as a reference. this means that any voltage between 0 and 5v is represented as numbers between 0 and 1024. If the signal you are measuring never reaches 5V it is possible to change  the reference  to an internal 2.5 v source and this divides the space between 0 and 2.5v in 1024 steps effectively doubling the resolution. If this still doesn't work for you then you can ask the processor to use an external voltage applied to aref. if you find a super stable 1V refernce source this will give you 1milli volt resolution for the ADC. this is used only in special applications because at that resolution the noise becomes a big issue etc etc

switching reference voltage requires adding a few lines of C code to your arduino code.

===========
cbi(ADMUX, REFS1); //clear REFS1 bit (0)
cbi(ADMUX, REFS0); //clear REFS0 bit (0)
===========

Reference:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1139161553/3#3

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1142283743

How to regulate voltage in a circuit

If your eletric parts need different voltage in a circuit, you will need to regulate the voltage. The easist way to do that is with a voltage regulator. It not only drops the voltage but also stablizes it.

A Voltage Regulator

You tube ttutorial

Reference:
http://www.afrotechmods.com/

Or you can build a regulator circuit which is basically built with a resistor and a diode. You need a NPN transistor to enable a larger current. Please see more in Reference.

Reference:
http://www.satcure-focus.com/tutor/page5.htm

 Any way you use to drop the voltage will cause heat. You should keep that in mind!

Sketch Uploading problem by Arduino Pro Mini 328P5V

When uploading our codes to Arduino Mini, we need an adaptor - Arduino MiniUSB - to accomplish it, in which we coonect the 4 Pins of both boards - the Gnd, +5V, RX, TX. But if you got problem to upload the codes to Arduino Pro Mini, please try this: connect one more Pin - the RTS of Arduino MiniUSB to RST of Arduino Pro Mini. It should work now.

Of course, you should choose the correct board typ in your arduino program.

Pins on theArduino MiniUSB

Arduino Pro Mini 328P5V

Sound Detector

Sound Detector

(NPN Transistor in sketch)

Connection

=== Arduino Code Sample ===

int DecPin = A5; // analog Input of Sound
int Val1;  // an initial value
int Val2;  // comparing value
int ValS = 5; // Sensibility
void setup() {
  Serial.begin(9600);
}

void loop() {
  Val1 = analogRead (DecPin);
  if (abs(analogRead(DecPin) - Val1) >ValS) { // if the read value changes
    Serial.println (analogRead (DecPin));   // print the value
    delay(50);
  }
}

====
Reference
Cheap Sound Sensor for AVR
http://tinkerlog.com/2007/05/20/cheap-sound-sensor-for-avr/

How to memory arduino data when power drops

Use EEPROM on Arduino
Be Careful!! The number of time to write EEPROM on Arduino is limited. Arduino supports usually at least 100,000 times EEPROM writing.
http://arduino.cc/en/Reference/EEPROM
http://arduino.cc/en/Reference/EEPROMWrite
http://arduino.cc/en/Reference/EEPROMRead

or on a EEPROM chip, for example a 16 kBit EEPROM chip by conrad.de
http://www.conrad.de/ce/de/product/150180/EEPROM-24LC16BP-MICROCHIP/SHOP_AREA_17311&promotionareaSearchDetail=005

reverse current / DC motor control with L293D IC

L293D IC

Pin Connections

L293D Can be used to control two DC motors. INPUT 1, INPUT 2, and ENABLE  1 (Ven1) controll the first motor which is connected to OUTPUT 1 and OUTPUT 2. Vs should be connected to the Power Supply for DC Motor which is higher than Vss and lower than 36 Volt. Vss should be connected to the Power Supply for the IC which is higher than 4.5 Volt. It's good to differ the power supply Vss from Vs. Ven must be higher than 2.3 Volt to enable the DC motor. It can be given by different Power to change the speed of motor.

Logic

Ven1 high & Pin 4 high & Pin 5 high = Stop

Ven1 high & Pin 4 low & Pin 5 low = Stop

Ven1 high & Pin 4 high & Pin 5 low = clockwise

Ven1 high & Pin 4 low & Pin 5 high = anti-clockwise

Ven1 low = Stop (not applicated)

PWM at Ven can be used to control the speed of Motor.

Connection Example

======Arduino Code Sample======
int switchPin = 2;    // switch input
int motor1Pin1 = 3;    // pin 2 on L293D
int motor1Pin2 = 4;    // pin 7 on L293D
int enablePin = 9;    // pin 1 on L293D
void setup() {
  pinMode(switchPin, INPUT);
  pinMode(motor1Pin1, OUTPUT);
  pinMode(motor1Pin2, OUTPUT);
  pinMode(enablePin, OUTPUT);
}
void loop() {
  // if the switch is high, motor will turn on one direction:
  if (digitalRead(switchPin) == HIGH) {
    analogWrite(enablePin, 255);    // analog output for different speed
    digitalWrite(motor1Pin1, LOW);   // set pin 2 on L293D low
    digitalWrite(motor1Pin2, HIGH);  // set pin 7 on L293D high
  }
  // if the switch is low, motor will turn in the opposite direction:
  else {
    analogWrite(enablePin, 150);   // analog output for different speed
    digitalWrite(motor1Pin1, HIGH);  // set pin 2 on L293D high
    digitalWrite(motor1Pin2, LOW);   // set pin 7 on L293D low
  }
}
==========================

Reference:
Controal a DC motor with Arduino and L293D IC
http://luckylarry.co.uk/arduino-projects/control-a-dc-motor-with-arduino-and-l293d-chip/
http://www.robofun.net/forum/viewthread.php?tid=6189
http://www.freewebs.com/isuru-c/motor_driver.htm

L293D IC by Conrad.de
http://www.conrad.de/ce/de/product/174003/?insert_kz=NA&hk=SEM&WT.srch=1&gclid=CJjz_7WA0asCFcK9zAod_molXA

http://www.conrad.de/ce/de/product/156134/IC-4-KANAL-TREIBER-L293D-STM/SHOP_AREA_17311&promotionareaSearchDetail=005

Important Webs for Design Prototype

Arduino HomePage
http://www.arduino.cc/    (Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.)

Processing HomePage
http://processing.org/    (Processing is an open source programming language and environment for people who want to create images, animations, and interactions. Initially developed to serve as a software sketchbook and to teach fundamentals of computer programming within a visual context, Processing also has evolved into a tool for generating finished professional work. Today, there are tens of thousands of students, artists, designers, researchers, and hobbyists who use Processing for learning, prototyping, and production.)

Fritzing HomePage
http://fritzing.org/   (Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to work creatively with interactive electronics. We are creating a software and website in the spirit of Processing and Arduino, developing a tool that allows users to document their prototypes, share them with others, teach electronics in a classroom, and to create a pcb layout for professional manufacturing.)