You also mentioned 30 or so feet of wire. That's likely also an issue with respect to electrical noise pounding away at the PC driver pin and eventually causing the output circuit to fail.
Although I only made a few of these boards and never did use the one on this web page the general idea is to make the sensor signals a bit more robust to noise and long wires. Perhaps the drawings can help. http://www.autoartisans.com/ELS/OptoSpindle.htm At a minimum buffer the TTL outputs with an SN7414. John > -----Original Message----- > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > Sent: February-22-23 8:41 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Parallel Port Current? > > Damage from over-current is cumulative. The bond wires that go from the > chip to the lead frame are VERY thin and will heat up and can only do this > for so many cycles. > > What you might try, to protect the other pins, is to use a higher value > current limiting resistor on the LEDs > > > > On Wed, Feb 22, 2023 at 8:30 AM Todd Zuercher <to...@pgrahamdunn.com> wrote: > > > I have an older Linuxcnc installation that uses a parallel port. It has 4 > > TCRT5000 optical sensors, that I was powering the IR LED with an output > > from the parallel port (and reading the IR sensor with an input.) It had > > been working fine for some time, but I only use this equipment once a > > year. This year when I drug it out of storage I could not get one of the > > sensors to work. After several hours of checking and rechecking every > > connection and trying multiple sensors, I figured out that the LED on the > > sensor that wasn't working simply could not draw enough current from the > > parallel port output to light bright enough, even though it had been > > working in the past. I switched it from pin14 to pin7 and full > > functionality was restored. Does this sound like I've partially ruined > > pin14 on the parallel port? (It still turns on and off.) Do different > > parallel port output pins have different current sourcing capabilities? > > > > I'm a little surprised that this happed to this sensor rather than the > > other 3, because it is fed through about 30 more feet of wire than the > > other 3 that are still working happily (fed by output pins 2-4.) > > > > I guess I should probably set up an alternate power source for the LEDs on > > the sensors, but they had been working fine before and I didn't feel like > > doing the additional wiring. > > > > Todd Zuercher > > P. Graham Dunn Inc.<http://www.pgrahamdunn.com/index.php> > > 630 Henry Street > > Dalton, Ohio 44618 > > Phone: (330)828-2105ext. 2031 > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
