Sine wave to ttl square wave

Hi
I have an anometer that that puts out an AC sine wave signal induced by rotating
magnet on propeller shaft. 80 mV p-p at 100 rpm. 8.0 V p-p at 10,000 rpm.
Output Frequency 3 c y c l e s p e r p r o p e l l e r r e v o l u t i o n (0.098 m/s per Hz).
Can anyone point me toward a suitable circuit that I could build that would convert the ac sine wave to ttl level square wave that could the be processed by an arduino.
Thanks in advance

Use an open collector LM339 comparator.

Ok this is what I have come up with so far thanks to Warpspeed over at www.thebackshed.com forum

Any comments? better image here

rubberbrick:
Any comments?

uhm.. what are R3, D1 & D2 connected to ?....

Seems to be the standard "Non-Inverting Comparator with Hysteresis" diagram on page 9 of the datasheet.
With added schottky diode clamp.

Page 8 of the datasheet:
"All input pins of any unused comparators should be tied to the negative supply."
Leo..

Sorry better drawing with where r2, d1 and d2 go, couldnt find ac symbol but it is as my first post.

Damn not have a good day here is the link hereSorry better drawing with where r2, d1 and d2 go , couldnt find ac symbol but it is as my first post ie 8v p-p at 176km/h.

Hi Wawa
Unyet this http://www.ti.com/lit/an/sboa204/sboa204.pdf and this guy here say otherwise, maybe different configs, it is a little over my head.
Thanks

I know you have to config non-used opamps that way, but an LM393 is a comparator, not an opamp.
I would go by the datasheet, and connect both inputs to ground.
Leo..

Shows how much I know, thanks