The freebie metal detector I previously designed for this blog is by far my most popular post. So here is another circuit I designed today.
Counters must be among the more sought-after electronic circuits. However, even the simplest of them are complex. This provides a “super simple” solution, to count from 0 to 43,200 on a quartz clock face (60 seconds × 60 minutes × 12 hours). It would be capable e.g. of counting attendance at most major public events. Almost any cheap analogue quartz clock is used for the display. IC1 provides suitable waveforms across R2 to pulse the clock’s tiny stepper motor M1. IC2 both boosts the current to M1, and provides test pulses to “IN” (a quick indication that the circuit is working). Note that the speed of the counter is limited to a few counts per second. C2/C3 are non-polar. The input at “IN” needs to be binary 12V, which means that the voltage needs to rise higher than 8V then lower than 4V for one count. The input at “IN” could be provided by any one of many detection circuits available on the Internet (I might design one for this blog if there’s a demand for a particular one). Note that before wiring up motor M1, its connections to its original clock circuit should be cut. The metal detector circuit is at http://thomasscarborough.blogspot.com/2008/05/bfo-metal-detector-1_21.html
NOTE: You may re-publish this design, on condition that you acknowledge the designer (Thomas Scarborough) and this blog (http://thomasscarborough.blogspot.com/).