Quote:
Originally Posted by harlequin2
If the tacho requires 2 pulses per rev, that actually makes the s/w to drive it a lot simpler using an o/p port and somethi ng that produces 33.3 pulses per 100A. I think!
I m ight just go and have another glass of wine now .........
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2 pulses per rev sounds realistic. My 83 VW’s tach uses that as well.
So assuming that, frequencies of 0 to 200hz (@6000rpm) need to be produced.
I’d use the PWM pin in digital I/O mode and bit toggle it based on timer interrupt. Timer 1 is unused in the PIC. It's 16-bit which when used with max prescaler of 8 allows generation of frequencies down to 1.9hz (9.5A on a 1000A scale). Resolution would be about 625 steps over the 200hz range.
If one chose to keep the fuel gage interface, this new tach interface could alternately use the alarm output. You’d loose alarm, but the overtemp Led still blinks at the alarm threshold. In either case you’d need a pullup resistor to +12V. I used a 1K on my tach input (from open collector hall switch) and it worked fine.
wine is fine, but liquor is quicker
-Chris