[sdiy] voltage and LEDs

[db]

>
>
>You'll want to use a power transistor, maybe a power darlington transistor 
>for the trigger switch.
>The 2N5088 won't handle that high of current.
>Using the 317 as a current source the LED goes to the "adj" pin not "Vout"


Ah, silly label error.

Any suggestion for a suitable transistor?


>..Or you can use the 317 as a voltage regulator, with some small R between 
>Vout and the LED, and put a small transistor switch in the resistor 
>divider that sets the Vout. Use that to electronically turn the 317 and 
>LED on/off.
>The datasheet has an example "5V Logic Regulator with Electronic Shutdown" 
>to give you an idea.
>http://www.national.com/ds/LM/LM117.pdf

http://yfrog.com/jvimage1jpj

So this new way would be to have the 317 do the big work, so a small 
transistor would do the switching?

In this '5V Logic Regulator with Electronic Shutdown' circuit, they show 
trigger is 'TTL.'
I am using a 2n5088 and it's working from my trigger. No reason not to use 
that 2n5088, right?

R1 stays at 240 and I R2 sets the voltage I need for the LED, yes?
Wouldn't this *shut* the power when it sees v+ at the base of that Q? Or am 
I still confused?




dennis.barton:skylab2000[socal]