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  1. 03-31-2008, 09:12 PM #1
    cesarfsim
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    Led current calculation

    Hello
    What is current (milliamp) in Master Iocard output ?
    I know the voltage is 5v and I want to calculate using differences voltage of leds.
    Thanks
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  2. 03-31-2008, 10:50 PM #2
    DaveC3
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    Take a look at this site. The electronic calculator has a resistance calculator for LEDs. http://electronics2000.co.uk/

    Dave
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    Thanks cesarfsim, Matt Olieman thanked for this post
  4. 04-01-2008, 03:14 AM #3
    pdpo
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    Hi,

    out of experience I found that the opencockpits outputs have an internal small resistance already. This means that the output voltage (5Volt) will drop a little the moment you start
    to take current from them (lighting a led) If I remember it well there was some 10 ohm
    internal resistance. If you only want to light one led with one input then you need to calculate the resistor by using the (5v - voltage over the led) / current for normal led operation
    in case you like to run two leds in series then the internal resistance limits the current enough
    so no need for a extra resistor.

    Greetz Peter
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  5. 04-01-2008, 07:05 AM #4
    Matt Olieman
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    Thumbs up Thank You

    Quote Originally Posted by DaveC3 View Post
    Take a look at this site. The electronic calculator has a resistance calculator for LEDs. http://electronics2000.co.uk/

    Dave
    The "Electronics Assistant V4.1" (FREE), very useful, thanks for the link
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  6. 04-01-2008, 09:23 AM #5
    wanderer
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    Quote Originally Posted by Matt Olieman View Post
    The "Electronics Assistant V4.1" (FREE), very useful, thanks for the link
    ... yes, but why does a "calculator" require access to the internet?!!
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  7. 04-01-2008, 10:11 AM #6
    DaveC3
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    You can download it and run it on your computer. Just click on the "Download" Tab at the top of the page.

    Dave
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  8. 04-01-2008, 11:12 AM #7
    cesarfsim
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    I have also a very nice online site to calculate resistors http://ledcalc.com/ but it needs de current in milliamp.
    The IOcards manual says resistor 330 ohms that's why I assumed it is 10 milliamp for one led 2.2 V
    Even using 2 leds they calculate for 2 resister of 330 ohms.
    I am not electronic expert bat I agree with Peter... 2 leds of 2.2 = 4.4... no resistor required.
    I just need the brightest light with secure not to burn it.
    Regards
    Cesar

    PS: I just order USB expansion card and one more master from Opencockpit.
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