Brighter LEDs

[AllenPitts]

Hello KlausST and the EDA board forum,

Thanks to KlausST for the excellent reply on the 'Changing Voltages' post.

The circuit that uses a PIR to activate a 555 timer which times the current
to lights in a closet works well. But used LED modules with a half dozen
5 mm thru hole LEDs. Have daisy chained four such modules but even
with two dozen 5mm LEDs there is not enough lumens to see if there is
salsa on my shirt.

The jump from nine to twelve volts increased the lights some but need
to take it to the next level.

From Mouser Electronics three Cree Starboards were received.

Mouser #: 416-XPGDWTH1HE8B1
Mfr. #: XPGDWT-H1-0000-00HE8-SB01
Desc.: High Power LEDs - White High Power LEDs - White Star 1x1 Wht 2700K 80-CRI 139lm
This one works with the nine volt tester


Mouser #: 416-MHDGWTN0HK427GB1
Mfr. #: MHDGWT-0000-000N0HK427G-SB01
Desc.: High Power LEDs - White High Power LEDs - White
This one does not work with the nine volt tester


Mouser #: 416-XPLAWTH0U40F8SB1
Mfr. #: XPLAWT-H0-0000-000HU40F8-SB01
Desc.: High Power LEDs - White High Power LEDs - White White, 2850K, 340lm XPL on Starboard
This one does not work with the nine volt tester

ALso tried the ....427GB1 and the ...0F8SB1 with twelve volt supply and 5 volt
hoping it was just voltage, no luck. Studied a "data sheet' that Mouser
had posted from Opulent America but all that was listed
was the CRI color rendering index and CCT correlated color temp.
No real electrical characteristics.

Finally found some data at Cree on the diode used by Opulent
in the StarBoard it was pretty slim:

It looks like the minimum forward voltage is around 2.5 to 3 volts so seems 12 volts, with a 100 ohm resistor, should
be more than enough to turn the two larger StarBoards on.

What am I missing?

Thanks.

Allen Pitts, Dallas, TX

 

[KlausST]

Hi,

I guess you need someting between 1W and 5W.
It seems the given LED may go up to 6W.

But only 3V. So if you use 12V supply, then you waste (12V - 3V) × I_Led.
Thus I'd say it may work but is not suitable.

To drive LEDs you need a series current limiting resistor.
4 LEDs in series makes 4 x 3V= 12V ... no room for a series resistor. Not suitable.

Thus I recommend 3 LEDs in series. Let's try 1W (3V type) each. Makes about 300mA. 3V/0.3A = 10 Ohms resistor.
The LEDs need proper heatsink. Also the resistor will dissipate 1W. I recommend at least a 3W rated resistor
To switch it ON/OFF or PWM dimming I recommend a MOSFET.
Simpke BJT will work, too, Darlington, too.

Klaus