mjkzz:
Yes, your objective is correct, however you are using a resistive load to simulate a non-resistive, non-linear load, LEDs, you get lucky to get same result.I call it a mess when using a current based switch in digital circuit -- looking at your "simulation" cicrcuit, your base current is rather large for a digital pin.
What luck? Current is current, the LEDs make for zero difference.
And the base current, approx 5mA, is well under-spec for a "digital pin" anyway that's sliced.
It's not unsound and it works.
Maybe it's "over-driven"; but that makes it "beta-proof" - no harm, no foul. Look what I have to work with here. smiley-tired_grin
adrian_h:
Looks like it's just a matter of trial an error then.
Calculations are just too complex unless I try to use that SPICE simulator mjkzz talked about, which would be another project in itself.
It's not "trial and error".
Just do what I've told you - and get the wires right.
I don't know how better I can make the point other than to have you send me the parts and do it for you.
This person managed to get with the programme --
IR Led - #21 by runaway_pancake - LEDs and Multiplexing - Arduino Forum