Looking for advice for an LED flag project

[Audioguru]

Batch? Are you buying from the LED manufacturer? The distributor might have a couple of years of batches all mixed up into one drawer.

 

[(*steve*)]

Not if they come on a reel or taped, etc.

Do they have a production packaging option?

 

[KJ6EAD]

Alright, I think I'm understanding a lot of what I'm being told here. I read the LED guide you posted earlier and it seems to be confirming all of my thoughts, but it did raise one question: how do I determine what current value I want if I'm connecting a bunch of LEDs in series (and this is referring directly to section 2 of that guide)? If the current determines the brightness, how can I know how much current will result in how much brightness (without testing the whole circuit)?

And as if right now I *think* I have a good idea of what I need to do to get my flag going, but I was going to run over the numbers with a few co-workers tomorrow to see what they say. If everything seems to be groovy, then thanks for the help!

I thought you had already determined the current values you need for the brightness you want with a small quantity of LEDs. If so, those values and the associated average Vfs remain the same. A different supply voltage or number of LEDs in a string only requires using that data to calculate new resistor values.

 

[Inglorious89]

I thought you had already determined the current values you need for the brightness you want with a small quantity of LEDs. If so, those values and the associated average Vfs remain the same. A different supply voltage or number of LEDs in a string only requires using that data to calculate new resistor values.

Maybe I didn't make it clear enough, but I didn't mean in relation to my project; the question was more in general then referring to anything specific.

 

[KJ6EAD]

Maybe I didn't make it clear enough, but I didn't mean in relation to my project; the question was more in general then referring to anything specific.

The LED datasheet has a graph showing the relationship between current and luminance but most people just hook up a sample to a potentiometer and dial-a-brightness by eye, then measure the current, voltage and resistance that has the desired look.

 

[KJ6EAD]

The datasheet has a graph of relative luminous intensity (no units) vs current but most people just hook up a potentiometer and dial-a-brightness by eye, then record the current and the resistance that achieved it with a fixed voltage supply. I try to string 6 or more in series to do this so I can derive a good average Vf from the data.

 

[Inglorious89]

The LED datasheet has a graph showing the relationship between current and luminance but most people just hook up a sample to a potentiometer and dial-a-brightness by eye, then measure the current, voltage and resistance that has the desired look.

Ah, that's what I thought it was. For the most part you gotta get the LED and tune it by hand, then measure the current.