Hi, Perhaps a bit more low-tech, how about an astable multivibrator? This circuit needs 2 transistors, 6 (or 7) resistors, and two caps. Add two LED's and you have a blinker. We used to build these out of leaded components on a 1.5 x 1.5 inch piece of perfboard. We had students who were in grade 5 assemble these from loose components, and they all got the circuit to work. The circuit can be built in one layer if you allow a single trace underneath one of the components.
On Sat, 2006-08-05 at 09:34 -0400, DJ Delorie wrote: > > Even just a little 555-based LED blinker or something would count as > > "functional" in this case, I think. > > 0603 cap = 1 cent > 0603 led = 7 cents > > Even the venerable 555 is too expensive in the small sizes appropriate > to this project (about $0.60). SOT-23 transistors come in at $0.10CDN at DigiKey in single unit quantities. > > Now, if you can think of a circuit that uses a flip flop and some > inverters, plus low-valued caps (even resistors cost 3x what caps > cost), that might be feasible. The success of this circuit depends on what `low' valued means here. To get visual frequencies, for a couple of Hertz we might need between 0.1 and 1 microfarad or so. We would have to breadboard the circuit to find out appropriate values for the cross coupling capacitors. (Although probably not with those 01005 components... ;-) > > (ok, so it's more than just a *soldering* challenge ;) -- -------------------------------------------------- Mike Jarabek FPGA/ASIC Designer http://www.istop.com/~mjarabek -------------------------------------------------- _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user