On Mon, 2012-02-20 at 17:42 -0500, gene heskett wrote: > 4. All logic outputs with the slots open > are sitting at about 18 millivolts.
The doc says "a high output when the optical path is clear", so something's definitely wrong... If that were my board, I'd expect the top-surface ground line running barely 25 mils from the screw terminal pads to be at least mildly shorted to all three output pins. Given the weak pullup, that'd hold all three to ground. With the power disconnected, are all three outputs isolated from each other *and* ground? With both polarities of the DMM? The bottom surface trace from the B terminal along those same pads may give you a clue. Whip out a magnifier and check that clearance. If you have a duplicate unsoldered board, check that one out... Is the board drawing (3 x 25 mA) for the LEDs + maybe (3 x 10 mA) for the detectors? If the detectors aren't powered up, that's a hint. If they *are* powered up, then their outputs are shorted to ground. The datasheet recommends a 100 nF cap "between VCC and ground near the device". That probably doesn't make much difference in a test setup, but I'd be superstitious and slap one cap in place across the board power input. Having just brought up a homebrew PCB, I never cease to be amazed at the wide variety of things that can go wrong. Like having to scratch off a tiny un-etched copper filament shorting a IC pin to ground *under* the IC; it was visible, but just barely, only after I soldered the IC in place. Before that, it wasn't there. [sigh] -- Ed http://softsolder.com ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
