variable reluctance sensor/speed switch

I am building a speed switch around a LM2907, but want to add a "pulse" LED
that blinks every time the magnet goes past the senor....I'm having a mental
blank, i'm sure it's easy but can't think how to do it! Should I
capacitively couple the signal from the sensor, so it doesnt mess up the
signal goint to the '2907 and use something like a schmitt trigger to flash
the LED? I know the output amplitude from the sendor varies greatly with
speed, but I need the LED pulses to make it easy to setup. Ant suggestions?

It is not likely you can drive the LED directly from the sensor - you
probably need some type of high impedance device like a mosfet to go between
the sensor and the LED.

--
Dan Hollands
1104 State Road
Webster NY 14580
585-703-2963
(E-Mail Removed)
www.QuickScoreRace.com
"stocky" <(E-Mail Removed)> wrote in message
news:uCRSa.7273$(E-Mail Removed)...
> I am building a speed switch around a LM2907, but want to add a "pulse"
LED
> that blinks every time the magnet goes past the senor....I'm having a
mental
> blank, i'm sure it's easy but can't think how to do it! Should I
> capacitively couple the signal from the sensor, so it doesnt mess up the
> signal goint to the '2907 and use something like a schmitt trigger to
flash
> the LED? I know the output amplitude from the sendor varies greatly with
> speed, but I need the LED pulses to make it easy to setup. Ant
suggestions?
>
>

My next thought was do I put the output of the sensor into an opamp and
drive it to a fixed level square wave, then feed that to the LM2907 and the
schmitt trigger (maybe via a cap). That would get me around the varying
input levels. yes?


"Larry" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> "Dan Hollands" <(E-Mail Removed)> wrote in message
news:<o5TSa.164294$(E-Mail Removed)>. ..
> > It is not likely you can drive the LED directly from the sensor - you
> > probably need some type of high impedance device like a mosfet to go
between
> > the sensor and the LED.
> >
> > --
> > Dan Hollands
> > 1104 State Road
> > Webster NY 14580
> > 585-703-2963
> > (E-Mail Removed)
> > www.QuickScoreRace.com
> > "stocky" <(E-Mail Removed)> wrote in message
> > news:uCRSa.7273$(E-Mail Removed)...
> > > I am building a speed switch around a LM2907, but want to add a
"pulse"
> > LED
> > > that blinks every time the magnet goes past the senor....I'm having a
> > mental
> > > blank, i'm sure it's easy but can't think how to do it! Should I
> > > capacitively couple the signal from the sensor, so it doesnt mess up
the
> > > signal goint to the '2907 and use something like a schmitt trigger to
> > flash
> > > the LED? I know the output amplitude from the sendor varies greatly
with
> > > speed, but I need the LED pulses to make it easy to setup. Ant
> > suggestions?
> > >
> > >
> A schmitt trigger would be a good way you will set the on time (LED)
> and at high speed the trigger would be so fast that you may not see it
> and as you noted the input loading would be reduced.
> Hope it helps