how does rpm sensor work?

[user]

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]

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]

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]

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]

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]

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]

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
-------------------------------------------------

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]

I doubt that a reed switch would be able to oporate at 250 Hz. A hall effect sensor
would be far more likly

Ziggy
------------------------------------------

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

[Keef]

It's definately a reed switch. I just bought a Powerball and after only 2 days it stopped counting RPM. I took it apart and tested the reed switch with a magnet and found it was not operating. I fitted a new reed switch and the counter started working again. It does require soldering skills to change the reed switch if you're thinking of doing it yourself.

Cheers,

Keef.

[Precession]

There is a tiny reed switch on the LCD counter board, you can even hear it clicking if you move the rotor around while you can see the string-hole. The magnet in the rotor is on the opposite side to the hole. Put your ear up close and move the rotor back and forth.