Dying Parallel port pins
T Chap
Posts: 4,198
Over a few days, two pins have now died on my PC parallel port. The cable runs to a board that goes into a Propeller via 1k resistors. There are 8 pins that goes into the Prropeller and also get sent to some motor driver inputs. Furtunately I had a few extra pins to swap out and keep running, but now I have no more spares. One more blown pin means I have to find another PC or parallel port PCI card if such exists. I have been hotswapping the cable. I meter between the GND on the cable and GND of the Prop boards and depending on how you go, it is either 12 or -12 from ground to ground (obviously this is with the cable unplugged). The PC and Prop PS are on the same AC strip.
The pins simply stay high when they die. Any suggestions on how hot swapping could do this to an output? Since they are exclusive outputs pins and never inputs, would an opto be the trick to solve the problem?
Post Edited (originator) : 1/25/2007 9:07:38 PM GMT
The pins simply stay high when they die. Any suggestions on how hot swapping could do this to an output? Since they are exclusive outputs pins and never inputs, would an opto be the trick to solve the problem?
Post Edited (originator) : 1/25/2007 9:07:38 PM GMT
Comments
Do you mean Serial Port? Parallel Port pins are 5V TTL level…+12V or -12V into them could damage them. Perhaps I am misunderstanding…Also; LPT ports are not friendly for hot swapping. On older computers this could result in the computer resetting on some systems. Optical isolation almost always helps in these cases. Take care.
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Chris Savage
Parallax Tech Support
If you really want to hot-swap, maybe you should make up a separate ground lead and use it to connect the two system grounds first, to try to get rid of that 12V difference, wherever it is coming from. That's what a lot of hot-swappeable cards do - their ground lead is extended physically so it is the first to make contact when you insert the card. Even if you were to use just a simple clip-lead jumper cable, I'll bet you'd do a lot towards preventing those pins from blowing.
If you do jump the two system grounds together, then what voltage difference shows between the pins? You don't still see any 12v, do you?
David