DI-194 (was Re: Data Acquisition newbie question)

[Don DRI05 Ricciardiello]

Just thought of why this won't work. My ignition is CDI and the voltage
going to the primary side of the ignition coil is not 12 V. What I do have
is a magnetic pick up like in page 7 but that is not a voltage output that
i'm after is it?

Don







The circuit on the top of page 9 of the datasheet will do that, almost
without modification.  The only components you'll need to change are R1
(which goes from pin 3 to ground) and C1 which goes from pin 2 to
ground.  The governing equation is Vo = Vcc * Fin * R1 * C1.  You want a
max Vo = 5V, and Vcc is 7.56V if you use the Zener regulation method
that this circuit uses (the 2917 has the zener option), and Fmax is
166.7, so that means R1 * C1 = 3.97e-3, but the exact value doesn't
matter because you can't get much better than +- 10% tolerance on
capacitors anyway.  So I recommend you make C1 0.1uf and R1 a 50k pot
(the target value is 40k with C1=0.1uf)  Vary R1 to calibrate the
circuit, I suppose you could use a regular tach for this, just watch the
output voltage at a fixed RPM and turn R1 until it's to your liking.
Or, just rev the bike to near redline and turn R1 until Vout is near 5V.

Brian


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