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PICList Thread
'RPM-Counter with flashing backlight'
1995\01\26@152314 by Conny Andersson

picon face
Jason Gorden wrote ...
> What did you use to count RPM?  Magnetic pickup?  How did you implement
> it on the PIC?

Well, I used the signal from the ignition coil (very simple huh) but it works
quite well. With a limiter/transient detector I managed to create a stable
input to the PIC16C55. Then I used the PIC as a frequency counter to get the
correct RPM-value. The "counting time" will vary with the number of
cylinders of your car and is about 0,3s with 4 cyls, so you will get a new
RPM reading every 0,3s (which I find a bit too slow).

The display has four digits and is VERY special. It's multiplexed (only 13
and it was probably used to measure the weight of vegetables and stuff like
The first two digits are now used as a peak RPM and the other two displays
the actual RPM. In addition to this there are five bars at the bottom of the
display and why not use them too ... (of course?)

This took about 3/4:s of the EPROM and to fill the PIC I included a
test-sequence-intro with flashing backlight in red/green/yellow and display
of all LCD-segments.

That's about it

Conny Andersson / Sweden

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