Parallel port 5v for logic supply

[stealthy]

Can I use the parallel port 5v safely to power a 5v logic.

Jim

[Mr.RC-CAM]

The LPT data I/O lines can sink and source low current (mA) at 5.0VDC levels. But most implementations use steering diodes to prevent bit toggles from messing up the power.

RC-CAM

[Markz]

Hello Jim,

I used the parallel port a lot during my college days... I almost always used some sort of buffer (ex. 74ls245, 7406, etc) with 10k pull-ups at the input to get best results. That's because some systems were verrrry slow to switch back to high - some were not even fully ttl compliant, with signals averaging between 1v for low and 3v for high. Schmidt-trigger buffers works best in that case.

On another topic, I have bought a very nice chip from delcom engineering (http://www.delcom-eng.com/products_USBIO.asp) which allows you to use usb instead of the parallel port in most applications. The outputs are very clean and fast enough for most applications. It works very well under Win2000 and XP.

Marc