4 digit auto-ranging frequency-meter.
Regulus Berdin email (remove spam text)
Dave VanHorn wrote:
> The displays are seven segment common cathode, it looks like a 4 digit
> multiplexed array, but four singles in paralell would work as well.
> The base resistors arent' critical, 470 ohm or 1k should work.
> The segment resistors are also uncritical, try 220-470. Depends much
> on the display efficiency.
> It's a cute project all right, hard to get less parts.
You can still minimize the parts by having the 7segment common anode,
make all the colllectors of the NPN transistors tie to the +5V supply
and reverse/invert drive to the LED (to the negative side). This way
the base resistors is not needed anymore.
See also: www.piclist.com/techref/index.htm?key=digit+auto+ranging
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