An old CD Rom drive can be a very useful source of some interesting components. One such component is a Hall sensor. These are 4 or 3 pin SMD components mounted right under the spindle motor. These help provide feedback to the motor driver so that it can drive the motor efficiently. This particular device has 4 pins, 2 for power and two provide a differential output. A simple differential amplifier can be used to amplify the small variation present at the output when teh device is in close proximity of a magnetic field. A simple circuit can be used to make the output a lot more useful to interface it with another circuit or perhaps a Microcontroller. I came up with the following:
A quick wire up on a breadboard :
And finally a video to see it in action:
September 5th, 2011 on 2:12 am
hola gracias por tu esquema esta interesante pero una duda todos los sensores de cd-rom son iguales (funcionamineto) me preguntaba si podrias explicar el patijalle de un sensor pero montado en su pcb original
gracias muy bien
September 5th, 2011 on 12:46 pm
Lo siento mi español no es muy buena.
try http://www.endrich.com/en/399/analogue+hall+sensors
1 – Output +
2 – Ground
3 – Output -
4 – + Power
Updated the circuit as power points and the marking on the sensor were missing.
September 6th, 2011 on 7:31 am
ok THANK YOU