I am wanting to experiment with high-power red-green-blue LEDs and have myself a LZ4-20MC00 (http://dk.mouser.com/Search/ProductDetail.aspx?R=LZ4-20MC00virtualkey62410000virtualkey897-LZ420MC00) for that purpose. First off I'm putting a regulated power-supply to the individual leds, just to see the effect of them. So I consult the datasheet and dial the 1.5a regulated power-supply in to match the specified max forward voltage - for the red color that's 2.96v, for example.
The thing is, the LEDs is rated 700ma for each individual LED. But at max specified voltage, with no resistor to keep anything down, I'm only getting about 400ma through my multimeter - how come? The datasheet doesn't state alternative ma's for each of the 4 leds inside the lens, and surely my power supply will happily offer all the led is willing to take on.
Those LED's are really not meant to be driven over 200 - 300 ma, you might need the next size up in the 12v form (which is just a series of these smaller led's only in an array)
As for it only drawing 400ma with .... I'd probably not go any higher!
at 2.96v, if you could find a data sheet on one of these led's you'd probably find a graph which shows the voltage / current draw, higher the voltage the current, know it up to 3.2v or higher and you'll reach
your magical figure....
let's suppose you were right, 2.96v is the correct forward voltage, that would imply your power supply is not able to deliver anything 400ma.... (I highly doubt it though) get your multimeter out and increase it to 3v, you should see around 500-600ma draw....
at 2.96v, if you could find a data sheet on one of these led's you'd probably find a graph which shows the voltage / current draw, higher the voltage the current, know it up to 3.2v or higher and you'll reach
your magical figure....
let's suppose you were right, 2.96v is the correct forward voltage, that would imply your power supply is not able to deliver anything 400ma.... (I highly doubt it though) get your multimeter out and increase it to 3v, you should see around 500-600ma draw....
Thanks a lot for your input,
that's the thing, the data sheet seems to imply the red led should be well able to take on the 700ma the thing is speced for (attached image) :-? At 2.95v I should be getting 1000ma out of it (which is the hightest rating in the datasheet - I haven't dared go above 3v, but I'm sure the amerage draw would increase if I did). Am I reading the data sheet wrong?
cjdelphi:
As for it only drawing 400ma with .... I'd probably not go any higher!
I should add that at 400ma it's ever so bright as I'd ever imagined it would be, so I'm certainly not disappointed by the unit - just trying to see how high it will go.
if you were extremely careful and can dial in the voltage (any jumps in voltage would cause it to max out and kill it very quickly, so unless you can do this, don't) slowly increase until you see a 700ma.. draw, then have a look at the voltage...
cjdelphi:
if you were extremely careful and can dial in the voltage (any jumps in voltage would cause it to max out and kill it very quickly, so unless you can do this, don't) slowly increase until you see a 700ma.. draw, then have a look at the voltage...
Hi again cjdelphi,
well I slowly cranked it up until I drew 700ma - at which point the voltage read 4.2v. That's in the extreme above the 2.95v that's specified as max in the data sheet.
I'm quite curious about it. The thing got hot, of course, but not more than I'd expect from a 10w RGB LED, not something that proper heatsinking wouldn't take good care of.
cjdelphi:
As for it only drawing 400ma with .... I'd probably not go any higher!
That line you wrote got me thinking twice about it. The median forward voltages specified for each die are approx, 2.5 + 7.6 + 3.8 = 13,9v * 0.7a = 9.73watts.
So - doh - of course I'm not meant to run each led at 700ma.
Thanks for your input, which helped me wrap my head around it.
