Calculating components in AMV

Discussion in 'General Electronics Chat' started by tommydyhr, Sep 3, 2010.

  1. tommydyhr

    Thread Starter Active Member

    Feb 3, 2009
    39
    4
    Hi there. I'm working on a test circuit in which I sometimes need to flash 6 LED's (3 by 3, alternately), and other times I need to flash 14 LED's (7 by 7, alternately). I'm constructing an AMV for the purpose (schematic attached), but I'm having trouble calculating the component values after the driver. It works mighty fine with one LED, but as soon as I attach two or more LED's it works strangely, or not at all. I really need to include a resister for every LED, so as to make sure the same current flows in every LED, no matter how many are attached.

    The LED's are on an external circuit board, but I included them in the schematic for illustrative purposes.

    How would I go by as to calculating the resisters to obtain 15mA for every attached diode, at any time (they're ~1.8V)?
     
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  2. tommydyhr

    Thread Starter Active Member

    Feb 3, 2009
    39
    4
    Never mind, I think I found a solution using a 555 instead :)
     
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