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View Full Version : how does rpm sensor work?

user
23-01-2006, 17:27
Hi

I would like to know how the rpm sensor in the gyroscope works. I know the gyroscope has a small magnet, but i would like to know if the sensor is a frequency sensor, a voltage sensor or something else. If somebody out there knows, please help me.
Thank you

Peace,
motaica
user
23-01-2006, 17:28
well, I really don't know, but I think that is a laser counter..
You know, if there are little hole in the moving part, it can cut a laser beam, and it inform the computer of the speed.

skydarking
user
23-01-2006, 17:28
There is a magnetic reed swich i think you'll find, encased within the rpm counter unit. Due to the nature of reed switches, no contact need be made between the switch and the gyro, so it doesnt slow it down etc.

Ben Heymink
user
23-01-2006, 17:28
while technically you wouldn't think it'd slow it down, it must to a small extent. I'm not sure how "small" the slow down is, but it wouldn't be more than a coupla revs per minute i wouldn't guess.

my reasoning is that you can't generate that small electronic signal in the "detector" without the energy coming from somewhere. It may be possible for someone to calculate how much energy it takes away from it, but i wouldn't worry :)

adam
user
23-01-2006, 17:28
There is a reed switch and clock reference built into the counter. I think there are also magnets in the gyro. Every time the gyro rotates the reed switch closes due to magnetism and bounces back open becuase the magnet in the gyro keeps moving. A microchip does some simple math to calculate an estimate of RPM by timing the number of switches per second (or so).

Kevin
user
23-01-2006, 17:29
The magnet is in the side opposite of the hole. I found this out cleaning out my powerball and one of the little screws was sticking to that side of the gyro.

486hawk
user
23-01-2006, 17:29
Are you sure it's a reed switch? I'd have thought it far more likely to be a Hall Effect Sensor (Solid state magnetic field sensor) as a Reed switch would buzz like a wossname...

Jamie
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It's a little reed switch alright...makes a tiny little 'clicking' noise that you don't really hear as the gyro spins - regards Clare
user
23-01-2006, 17:29
I doubt that a reed switch would be able to oporate at 250 Hz. A hall effect sensor
would be far more likly

Ziggy
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Reed it is actually Ziggy...humming away nicely at the current 15K+ levels..!