DRAC simple design

[Kevin Margitta]

I was in need of a DRAC earlier in my conversion, yet ended up not needing
it thanks to some great help.  A design I had in my head (never tried) was
pretty simple. the output from the tranny VSS is a screwey sinewave.. send
that signal into a frequency to voltage converter, (national semiconductor
makes a nice one, LM2917 I think).. it has a linear output voltage dependent
on it's frequency output. That output voltage can feed a Voltage Controlled
Oscillator (VCO) like a 566 which can make a nice clean square wave for your
ecm/speedo. There can be a pot (10k?) between the 2917, and the 566, and by
controlling the pot, you can control the ratio... just use math for all the
calcs.. and drive next to someone for fine tuning.

I remember someone telling me about an easier way using a simple Phased Lock
Loop.. but haven't thought much about it.. it may use less parts.. but I
would think my idea should work, and is infinately variable to make up for
inaccurate speedo's

Kevin Margitta
3800 series II s/c, Lesabre T-type, 88