speedo converter needed

[Charles Morgan]

Mike, if you only need to frequency divide then you could use a simple
binary rate multiplier like the SN7497.  SN7497s  can be cascaded to
provide whatever resolution you need.  One potential problem with a binary
rate multiplier, however, is that it divides synchrounously and hence
introduces jitter unless the division is by a multiple of 2.  If you need
to both frequency divide and multiply, and do it asynchronously, then you
can use a multiple timer PIC (like the 16F87X that has been discussed
recently) and set the timers to overflow at different rates (let me know if
you want more details).   If you really want to set the frequency with a
pot, then you could use a frequency-to-voltage converter like the LM2917
followed by a voltage-to-frequency converter like the LM331, with a trip
pot in between.

Charles Morgan

At 07:40 PM 6/9/99 -0700, Mike Pilkenton wrote:
>Does anyone have a simple frequency converter circuit that could be used to
>calibrate a typical inductive pickup signal to the proper frequency based on
>different tire and gear ratios?  I envision a circuit that would use the
>stock pulsed signalk from the tranny and then provide a fine tuning trim pot
>that would vary the frequency up or down based on the above parameters.