Does anyone have any good ideas for protecting a PC parallel port?

Other than:
- Opto-isolators (need to keep cost and board space lower) or
- Series resistor, 5.1v zener to ground and reversed diode to Vcc (would
like better protection and again, board space)

This is for a kit so all through hole or very large SMT.

Here is my current wild idea:

I'm thinking about putting tiny little T1 or T1.75 lamps in series with each
pin...
- Rated at 5volts, so if you short a pin, the lamp lights up which increases
resistance and dissipates the load.
- The fact that it is lit tells you that you pulled a dummy.
- And if you really do something scary, they pop just like fuses.
- Less than a nickel a pop.

Seems like a great idea, but I've never seen it used for port protection so
it makes me nervous. Maybe the port could be blown before the light heats
up?

My dad did it many times with power supplies and other such things using
larger bulbs, etc... Always worked fine for him. The resistance of a
standard incandescent bulb can go from just about zip (at about 25% of
operating voltage) to several K ohms when fully on.

---
James Newton, webhost piclist.com (former Admin #3)
jamesnewton@piclist.com 1-619-652-0593 fax:1-208-279-8767
PIC/PICList FAQ: http://www.piclist.com or .org  PBK

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu