Nathan,

I've used the LM339 in my last two projects.
I had the same problem you did! You need a pull-up
resistor to +5VDC. That should solve your problems.
Try around 1K.

Best regards,
Steve

Steven Kosmerchock
Radio Frequency Systems
Phoenix  Arizona   USA
www.rfsworld.com

www.geocities.com/researchtriangle/lab/6584

-----Original Message-----
From: Nathan Hendler [mailto:pic@RETARDS.ORG]
Sent: Wednesday, May 03, 2000 11:49 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Comparator -> PIC interface

Ok, this is real basic stuff I'm sure, but I'm wondering if anyone has a
circuit showing how to interface an LM339 to a PIC?  Do I need a pullup
resister between the two?

For some reason I'm just not getting the comparator to swing between 0 & 5
volts for the PIC input.

Thanks,
Nathan Hendler