Tachometer

[EADracer]

Need a non-contact tachometer to measure the rpm of small rc racing motors.

Any ideas welcome

 

[Boncuk]

Use an IR-beam and depending on the motor (aircraft with propeller) or car model the measuring method will differ slightly.

With a propeller you can make an IR barrier to count the blade passages and with a car motor you can use the same device as a reflective IR-barrier by glueing a piece of reflective material (aluminum foil) onto the shaft to measure.

Modulate the IR-diode at approx 30 to 40KHz and use a Vishay TSOP17XX as receiver to make the device independent of daylight and artificial light sources.

Boncuk

 

[user_88]

If you have an O-scope and a hall effect sensor, you can attach a short piece of bar magnet to the rotating shaft....and measure the time elapsed between successive pole passes. A short collar and a set screw will work...Use epoxy or glue to attach the magnet to the temporary collar.

 

[wizard]

Yeah, You can simply use a Hall effect sensor to do so.

2 years ago I made one using a hall effect sensor I picked up from a computer Fan. I used a calculator as the counter.

 

[user_88]

Yeah, You can simply use a Hall effect sensor to do so.

2 years ago I made one using a hall effect sensor I picked up from a computer Fan. I used a calculator as the counter.

Were you able to actually get a calculator internal clock circuit pulse to increment a counter ... for a given time interval? ..... Or maybe just use the Hall sensor pulse to add +1 to a calculator memory register..using a keypad trace ...for a given time period...

 

[wizard]

Were you able to actually get a calculator internal clock circuit pulse to increment a counter ... for a given time interval? ..... Or maybe just use the Hall sensor pulse to add +1 to a calculator memory register..using a keypad trace ...for a given time period...

Sorry I were too busy and did not get any time to come here for these days,

well, the story goes back to when I did not have any scope. then I used a Cheap engineering calculator to do the job. I used the second trick you mentioned.

the calculator were exchanged to count the numbers of turns of windings and then I used it as a tachometer to measure the RPM of several motors which I wanted to use in my indoor plane designs.