[Diy_efi] function generator for shutterwheel

Carter Shore clshore
Wed Dec 28 02:16:04 UTC 2005


Some function generators have an FM input, ie, output
frequency is proportional to voltage. A properly
shaped voltage (from a secondary function generator)
will create the waveform you are looking for. 
An alternative is to create the digital waveform you
seek, (ie, a sequence of 35 50% duty cycle pulses,
followed by a missing pulse, repeat, repeat, ...). Run
this signal through a low-pass filter to get a quasi
sinusoidal wave. But your range of frquency will be
somewhat limited, and amplitude may vary quite a lot.
Brute force method is to chuck up the toothed wheel
into a variable speed drill or lathe, and use the
stock pickup.

Carter

--- Phil <philhunt at comcast.net> wrote:

> I want to drive a VW management system on a benchtop
> mockup for testing and development purposes. I need
> a function generator that mimics the crank senser:
> i.e: a sine wave of 30 or so cycles (haven't counted
> the teeth yet) punctuated by a missing point. I'll
> need to be able to change the frequecy to mimic rpm.
> I already have a function generator-is there some
> kind of simple circuit I could process it's poutput
> with? Phil, Phil's Foreign Car, Kenvil, NJ USA  973
> 584 0161>
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