Clyde, You are right, just because I said this solution would work doesn't mean it is the best one. It's definately a different approach though. I like to consider a analog solution every once in a while so I don't get caught up in the trend to make everything under the sun digital. It reminds about an AD I saw in one of those magazines that sells products that didn't quite make it in the real marketplace. The AD was for an Electronic Cat Litter Box. It boasted that the box was computer controlled to clean itself 10 minutes after your cat exited. What A Waste of Processor Power! :) Price you ask: $149 US (On Closeout) Seriously though, he could use an 8 channel serial A/D convertor. (Sorry don't have any part number but I know they exist) An 8 bit A/D convertor would have no trouble recognizing 20 distinct voltage levels, yielding a max total of 160 switches. This would only require 2-3 I/O pins and cost ~$1-3.00. Also I think it might be possible to use the same value resistor for all the switches, and so it could just be built into the switch. This also has the advantage of using less hookup wire then a matrix approach, just one set of wires for each of the eight sections. Ben, Ben Wirz Check out My Home Page for Great Deals on Bulk Buy's Nitinol Wire, LMD 18200 H Bridge and 10 Mhz PIC 16C84 blw2@cec.wustl.edu http://cec.wustl.edu/~blw2/index.html On Tue, 7 May 1996, Clyde Smith-Stubbs wrote: > Ben L Wirz wrote: > > > How about a series of switches wired in parallel. Each switch would > > add a different amount of resistance. Apply +5V to one side and read the > > output voltage returned with a A/D convertor. A clever choice of resistor > > Yes, but this requires an A/D converter - seems a little like overkill. > Plus, it would be failure prone, since if any resistor changed value > you'd be stuffed. > > But then, maybe I'm just taking the suggestion too seriously :-) Where > was your tongue, Ben? > > Clyde > > -- > Clyde Smith-Stubbs | HI-TECH Software, | Voice: +61 7 3300 5011 > clyde@hitech.com.au | P.O. Box 103, Alderley, | Fax: +61 7 3300 5246 > http://www.hitech.com.au | QLD, 4051, AUSTRALIA. | BBS: +61 7 3300 5235 > ---------------------------------------------------------------------------- > For info on the World's best C cross compilers for embedded systems, point > your WWW browser at http://www.hitech.com.au, or email info@hitech.com.au >