In SX Microcontrollers, SX/B Compiler and SX-Key Tool, DigitalDj wrote:

Give this a try!
 

Parts Needed:
1 x 9V Battery
1 x Standard 3.5mm Male Plug for headphone jack
1 x 100K Resistor 1/4W
1 x 22K Resistor 1/4W
1 x 470 Resistor 1/4W
1 x LED (or 2)
2 x General Purpose NPN Transistors BC547


[img]http://www.runtimeerror.net/blinky/images/blinkyscheme.jpg[/img]

This is essentially a simple darlington pair amplifier to drive up the current and voltage coming from a soundcard's headphone jack.
2 LEDs can be used while still keeping things looking fairly decent. More LEDs can be added in parallel, but be sure to keep an eye on the current draw. Voltage can be adjusted to 5volts and change the curent resistor. You vould feed this into the SX with the 5volt supply but not any higher.

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