MCE questions - vf / ma

[aljsk8]

i wont bore you with the detail

i have driver i have mce's (series stars) im suposed to measure resistance across certain points on my driver do some maths and get a current - the figures arnt working

if i crank the driver up to max (an unknown amout on a trimpot)
the vf of one of the stars is 13v

is there any way i could be driving this at more than 700ma?

if so is there any chance on earth i could be be driving this at more than 1000ma?

 

[Christexan]

The question is not terribly clear, however the simple response is yes, to both...

If you measure the voltage on both ends of the star (not the driver) and measure 13F across the package, then it's very possible you are driving it at, above, OR below the figures you asked.
Now, what is EXPECTED? MC-Es seem to have typical Vfs of around 3.4/die at 1A (correct me if I'm wrong there, but it's typical for most Cree dice, 3.4-3.6). You have 4 of them, which is 3.4*4=13.6V.
When hot, the Vf falls quickly... so if these are heating up (poor heat transfer to ambient), then it could easily be 3.2*4=12.8.

So yes, it's easily concievable that at either 700mA, or 1A, a Vf of 13.0 is reasonable.

If you are trying to determine the actual current based on the Vf, it's impossible to calculate accurately that way, every LED die is different in it's Vf/If ratio, and it changes significantly depending on junction temperature, binning, etc.

 

[Hack On Wheels]

Why not put your multimeter inline with the MC-E from the driver? Should be fairly easy to read the current...