Post by thread:RPM-Counter with flashing backlight

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 lines) and it was probably used to measure the weight of vegetables and stuff like that. 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