Hello! I am using the TLC5940 Tutorial (Arduino Playground - TLC5940). I understand most of it, but I don't understand the 2Kohm resistor used to limit current. I would like to use external current limiting resistors (which I understand). So, what value of resistor should I use in place of the 2Kohm if I want to use external current limiters? The amount and voltage of the LEDs will vary by pin, if that matters. And also, if it matters, some pins of the TLC won't have LEDs.
Thanks!
Ethan
The whole point of the TLC5940 is that it has a constant current driver. The single resistor sets the current for all the LEDs. Just because you currently don't understand it is no reason to abandon it. I am not even sure if what you are asking is possible, I know it is not desirable. You will in effect be driving the constant current drive outside it's normal operating conditions.
Look at the data sheet and see what vale of resistor you need for the current you want, there is a graph so you don't have to touch any scary maths.
That graph helps immensely! Just a couple more things. Will I need to make adjustments if I don't use all the driver pins? And can I use different voltages on each driver pin?
Thanks for your help!
Will I need to make adjustments if I don't use all the driver pins?
No.
And can I use different voltages on each driver pin?
Well I have never thought about that but providing they are all less than 12V (I think check the data sheet as it could be 17V) then I don't see any reason why not. Make sure all the grounds are together.
Great, thanks!
P.S. I believe that they are meant to sink voltage.
I believe that they are meant to sink voltage.
No they sink current.
Sinking voltage is a phrase that doesn't make sense.
Oh, sorry. :-[ I am still getting into Electronics.
No worries we all have to learn it.