IR LED setup@ 6V

[airman00]

I am currently using this setup with my IR reflective sensor http://www.superdroidrobots.com/product_info/qrb1134.htm

Now I want to switch from 5V to 6V

There are two resistors which I am unsure what value they should have:
There is a 220 ohm resistor going to one IR LED and a 10K ohm resistor acting as a pull up resistor.
Those values were meant for 5V , but what values should they be at 6V???


Thank You

[bens]

You don't need to change your resistor values.  Your IR LED will be slightly brighter, but that's not a big deal.

[airman00]

You don't need to change your resistor values.  Your IR LED will be slightly brighter, but that's not a big deal.

Thanks, I did a test on my own , and the IR leds were fine


how do you calculate the LEDs proper resistor?

[ed1380]

http://led.linear1.org/1led.wiz

[bens]

how do you calculate the LEDs proper resistor?

And here's another site: http://home.cogeco.ca/~rpaisley4/LEDcalc.html

In general, you want a few milliamps (maybe 2 - 20 mA?) running thorugh your LED.  The higher the current, the brigher the LED will be, but the faster it will burn out.  To calculate the current passing through your LED you can use Ohm's Law: I = (V - LED voltage drop)/R

Typically LEDs have a voltage drop of between 1 and 3 V, depending on their color (the higher the energy of their color, the bigger the voltage drop).  As long as you're in the low milliamp range, you can always try a current and see how bright your LED is (assuming it's visible and not IR, of course), then adjust the resistor accordingly if it seems too bright or dim.

[ed1380]

yep up to 20mA for regular led's, but I have this super bright one that uses 30 

[Admin]

http://www.societyofrobots.com/electronics_led_tutorial.shtml

You can also use ohm's law given the known current and resistance for the old voltage, then recalculate resistance for the new voltage.