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Team:Brown/Modeling/Light device
From 2010.igem.org
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.
