[Diy_efi] Looking for some help on a speed sensor project

[Scott Campbell]

Hi Howard,

It sounds to me like you need a frequency to voltage
converter, followed by an opamp.  

Feed the voltage output from the F/V converter to one
of the inputs on the opamp.  Connect the wiper lead on
a pot to the other input of the opamp and the other
pot leads between power and ground.  Follow the opamp
with your favorite transistor to provide the necessary
current for the relay.  This will give you a frequency
controlled switch that you can adjust across a wide
frequency range.

Conceptually simple enough... now the hunt begins for
suitable F/V, opamp, transistor, resistors, caps, 
protection diodes...

Scott.

--- "Saxon, Howard (AFS-Warren)"
<Hsaxon at afs.bwauto.com> wrote:
> Hello all.  I'm not too good at this but I'll try to
> describe what I want
> and what a "semi-knowledgeable" friend told me I
> need.  What I'm trying to
> do is trip 1 or 2 relays based on car speed, not
> RPM.  The car's speed
> sensor operates like this.  There are 2 contacts. 
> One is grounded and the
> other has 5 volts going to it.  Contacts inside
> close 8 times per revolution
> and the sensor internally rotates 1000 times per
> mile, so it puts out
> approximately 8000 pulses per mile.  What I need is
> to somehow turn on a
> relay at a certain "pulse per time" or speed and
> have it turn off if the
> speed drops below that point again - and have it
> adjustable so I can fine
> tune the car.  My friend said that, for starters, I
> need a "frequency
> counter" and then a way to convert that to a
> switchable signal.  Any help
> would be greatly appreciated.
> Thanx a lot,
> 
> Howard Saxon	
> Senior Designer
> Advanced Products
> Borg Warner AFS
> 810-497-4026
> hsaxon at afs.bwauto.com <mailto:hsaxon at afs.bwauto.com>
> 
> 
> 
> 
> 
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=====
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