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Illumination device design

This prototype device uses two super-bright blue LEDs (470nm, 2400mcd) to illuminate cells. It will be used to drive the LOVtap promoter, which is responsive to blue light. The device is controlled by an open-source Arduino Duemilanove microcontroller and can be custom-programmed to cycle through various light states for various amounts of time.

The Arduino Duemilanove

The Arduino Duemilanove ("2009") is a microcontroller board based on the ATmega328 (datasheet)The Duemilanove has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button.

• Operating Voltage - 5V
• DC Current per I/O Pin - 40 mA

Calculating the proper resistor

The LED we used has a forward voltage of typically 3.5V with a max of 4V. The Arduino Duemilanove outputs at 5V. Thus, we used the resistor calculator located [http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng here] to calculate the proper resistors to use:

We only had a limited number of resistor types in stock, so we used a 56 Ohm resistor. The light output was not as bright as we wanted, so we switched to a 37 Ohm resistor. This may stress the LED more than usual, but should be enough resistance that it will not easily burn out.

Source code

/*
Light Induction Device
Turns on an LED on for a specific amount of time, then off, and repeats The circuit: * LED connected from digital pin 13 to ground. * Note: On most Arduino boards, there is already an LED on the board connected to pin 13, so you don't need any extra components for this example. */ int ledPin = 13; // LED connected to digital pin 13 int ledPin2 = 12; // LED connected to digital pin 12 // The setup() method runs once, when the sketch starts void setup() { // initialize the digital pin as an output: pinMode(ledPin, OUTPUT); pinMode(ledPin2, OUTPUT); } // the loop() method runs over and over again void loop() { digitalWrite(ledPin, HIGH); // set the LED1 on digitalWrite(ledPin2, HIGH); // set the LED2 on delay(14400000); // wait for 4 hours digitalWrite(ledPin, LOW); // set the LED1 off digitalWrite(ledPin2, LOW); // set the LED2 off delay(14400000); // wait for 4 hours }