Speed Sensor for my project

[goodboy]

Hi guys,

I am a final year automobile engineering student. I have to make a speed sensor for my project. I am thinking of making a magnetic pickup type sensor. I came across an article abt making this sensor using the windings of a relay. So I think, I am good upto the sensor. Can someone tell me how to process the sine wave output(i.e. converting to square wave and then processing). The objective is to get the speed of the output shaft of a gear box and energize a solenoid when the required speed is attained. I dont know much abt electronics. But I ve a lot interest. So please help me. Thanks

 

[Mr RB]

The coil pickup and rotating magnet will produce a sine like waveform, that gets a higher amplitude at higher speeds.

Your easiest solution is to rectify the AC sinewave with a diode, then filter into a capacitor, you will get a DC voltage that rises at speed. Then you just need a voltage comparator to set the threshold point.

 

[Vizier87]

..and you also can use a frequency-to-voltage converter like the LM2917. But it costs more though.

 

[goodboy]

The coil pickup and rotating magnet will produce a sine like waveform, that gets a higher amplitude at higher speeds.

Your easiest solution is to rectify the AC sinewave with a diode, then filter into a capacitor, you will get a DC voltage that rises at speed. Then you just need a voltage comparator to set the threshold point.

Thanks for the quick reply. I thought only the frequency changes with increase. Can u pls explain how the amplitude varies. A link would do. Can u gimme a step by step procedure. Again couple of links ll do Thanks

 

[Space Varmint]

If you want straight digital pulses generated from your mechanics you could use an encoder disc. It's like a cardboard wheel with holes around the edge. Then you shine an LED through the edge and a photo-detector on the other side of the wheel so that as the wheel spins faster the pulses will increase in intervals and decrease in pulse width.

 

[goodboy]

If you want straight digital pulses generated from your mechanics you could use an encoder disc. It's like a cardboard wheel with holes around the edge. Then you shine an LED through the edge and a photo-detector on the other side of the wheel so that as the wheel spins faster the pulses will increase in intervals and decrease in pulse width.

U mean it gives square wave directly?

 

[Space Varmint]

Yes. Pulses per say. I bet you never seen a "View Master". They were cool. You could see pictures in 3D. The disc that the pictures were on looks exactly like an encoder disc.

 

[ericgibbs]

as the wheel spins faster the pulses will increase in intervals and decrease in pulse width.

hi SV,
I think you may have a typo..

 

[MikeMl]

Hi guys,

I am a final year automobile engineering student. I have to make a speed sensor for my project. I am thinking of making a magnetic pickup type sensor. I came across an article abt making this sensor using the windings of a relay. So I think, I am good upto the sensor. Can someone tell me how to process the sine wave output(i.e. converting to square wave and then processing). The objective is to get the speed of the output shaft of a gear box and energize a solenoid when the required speed is attained. I dont know much abt electronics. But I ve a lot interest. So please help me. Thanks

Look at this previous thread. Replace the motor winding V1 with your pick-up coil.

 

[Reloadron]

If this speed pick up is what you had in mind that will work out perfect with the link MikeMl provided. That is a slick little circuit! You end up with nice 5 Volt pulses. Again, slick circuit!

Ron

 

[jbeng]

Have a look at this old thread where I showed the magnetic speed sensor I made from an old relay coil and a magnet, just like the Instructables link. It's about halfway down the page.

 

[goodboy]

If this speed pick up is what you had in mind that will work out perfect with the link MikeMl provided. That is a slick little circuit! You end up with nice 5 Volt pulses. Again, slick circuit!

Ron

This is exactly wat I had in mind

Look at this previous thread. Replace the motor winding V1 with your pick-up coil.

Have a look at this old thread where I showed the magnetic speed sensor I made from an old relay coil and a magnet, just like the Instructables link. It's about halfway down the page.

Thanks guys. I ll post if I get any doubt.