tachometer question v8-v6

[Ludis Langens]

Terry K <terryk at foothill.net> wrote
>The LM1819 stuff is on the net at National Semicompactor. The tach schemo
>is in the data sheet. But it is PDF. 

Where?  I looked on the National web pages a few days ago (when this part
was first mentioned.)  I couldn't find mention of an "1819" - either with
the search engine, or by browsing.

Adding some useful info:  Some time ago I traced out the schematic of the
tach in my car.  It uses a 16 pin chip - perhaps this LM1819.  First there
is a freqency to voltage stage.  Then there is an (analog) voltage to
dual coil gauge driver stage.  The FtoV works with an RC circuit.  The C
is probably 0.033 uF.  The R is on the top layer of a hybrid resistor pack.
It looks laser trimmed.  Considering that the cap needs to have a low
thermal coefficient, I'd change the resistor when converting a tach.
(Unless you're a tech at NASA or someplace...)

                   unsigned long BinToBCD(unsigned long i) {unsigned long t;
Ludis Langens         return i ? (t = BinToBCD(i >> 1), (t << 1) + (i & 1) + 
ludis at netcom.com                 (t + 858993459 >> 2 & 572662306) * 3) : 0;}