Optical Rpm Sensing

[wawoodman]

I have one of the handhelds that brino mentioned, and it's pretty convenient. Much cheaper than installing a tach on the lathe, mill, drill press...

 

[francist]

Quite some years ago I made a reflective-type tachometer using a visible light LED and photo resistor. Considering it was a handheld unit and I was trying to check speeds of a wind turbine whirling around in my backyard it worked surprisingly well. In a fixed scenario it would lots easier to get the focal lengths correct. Foil HVAC tape makes for really good reflector material.

-frank

Edit- meant photo transistor, not resistor.

 

[John Hasler]

For a reflective optical transducer you want one of these:

http://www.digikey.com/product-sear...ical-sensors-reflective-analog-output/1967052

For magnetic gear tooth sensing you want one of these:

http://www.digikey.com/product-search/en?FV=fff4001e,fff80480&k=gear+tooth&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&pbfree=0&rohs=0&quantity=1&ptm=0&fid=0&pageSize=25

 

[wa5cab]

I wrote "reluctance" but I was more specifically thinking of eddy current, which will work with any conductive material, including Zamak.

 

[Azbrewer]

I have never had any dealings with eddy current but what I have seen today it looks promising. More research is in order.

 

[John Hasler]

I wrote "reluctance" but I was more specifically thinking of eddy current, which will work with any conductive material, including Zamak.

Aren't those a bit pricey?

 

[wrat]

Aren't those a bit pricey?

Take one off of any car wheel in the last 10 years. Antilock brakes all use reluctor rings that are some kind of pot metal on the back of the disc brake rotor.

Wrat

 

[John Hasler]

Take one off of any car wheel in the last 10 years. Antilock brakes all use reluctor rings that are some kind of pot metal on the back of the disc brake rotor.

Wrat

Far as I know those are all Hall-effect or reluctance, not eddy current.

 

[Azbrewer]

As I am using an Arduino I have to stay with logic level components(5 volt).

 

[wa5cab]

It only takes one transistor and three resistors to make a level changer. However, I am not certain about the I/O requirements of the ABS sensors. They are certainly cheap enough. And definitely sturdy enough.