Angelsfall

I am building a project for my college graduation project consisting of a simple parallel circuit and a VB program built. I am communicating to the circuit board with the VB project VIA parallel port. I built the simple parallel circuit, putting the leds directly on the board in the circuit and ran the VB program.

Problem is I am getting constant current (or voltage) to the LEDs. On the VB program I click on one button for that certain light and it should turn on, however whenever my circuit board is hooked up to it, the light immediatly comes on.

The way it is hooked up is for each LED I use a wire from the parallel cable for that LED (ex: LED 1 uses pin 2, LED 2 used Pin 3, etc.) The black (ground) lead from the parallel port is hooked up to the other end of the circuit that is completed with 100 ohm resistors between the LED and the ground.
I have a a sketch of the circuit attached if this is not explained well enough. If anyone has any ideas please let me know ASAP, as my graduation is coming up very soon and I need this project completed to
graduate!

Thanks in advanced!

Attached Images

untitled_500.jpg (15.4 KB, 95 views)

johnbprice

Try this http://www.lvr.com/jansfaq.htm
or http://www.lvr.com/parport.htm