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reuse38 / clockthree

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HW: Biasing Transistors to increase LED brightness #14

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
I used 2N5415 transistors (rated for 1A) instead of 2N5401. Brightness improves 
a bit.

I also reduced the resistors connected to the Base of the Transistor from 100 
Ohms to 33 Ohms. This drives the transistors better, and the LEDs are much 
brighter.

Original issue reported on code.google.com by anoo...@gmail.com on 14 Dec 2010 at 8:01

GoogleCodeExporter commented 9 years ago 
Using ZTX935 rated to 3.5A does not produce WHITE.

Best setup -- base resistor ~ 21Ohm, r_ext ~1K4 Ohms.  Pink and not too much 
brighter.

I get the feeling that when we try to overdrive LEDs red wins.

Good news is this can save us $200.

Original comment by wyojus...@gmail.com on 23 Dec 2010 at 4:33

GoogleCodeExporter commented 9 years ago 
Other transistors have a much larger "white range" in that r_ext can have a 
much larger range of values while maintaining brightness: 1K3 to 10K Ohms.

Original comment by wyojus...@gmail.com on 23 Dec 2010 at 4:38

GoogleCodeExporter commented 9 years ago 
Closed on TJS final board review

Original comment by wyojus...@gmail.com on 5 Jan 2011 at 12:42