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Finding Hall Effect Switches
Printers and Fax Machines
Occasionally, you may find that Hall switches have been used.
If used, they are typically found used for cover open and paper-out detectors.
Floppy Disc Drives
The most comon place I find Hall devices is in floppy disc drives.
They are typically used to indicate INDEX.
This is done bby placing a magnet on the disc motor.
This passes the Hall device once per revolution.
The Hall switch is indicated on the above picture of a 3.5 inch disc drive motor.
This is typically what you would see on many drives from many manufacturers.
Above, you can see the hall switch and magnet.
Above, you can see the connections between the pcb and hall device.
Above is front view of the hall switch, showing the part number.
The data sheet is available on the data page.
Let me know if you need any help identifying the parts you find.
Above, another brand of disc drive and it's hall switch.
Notice that the magnet is held in the outer plastic rim.
Above, the hall switch removed, showing part number.
Please read the next section - USING - before disconnecting the device.
When stripping the disc drive, carefully remove the magnet from the motor.
These are normally quite small and useful to trigger the hall switch again.
OTHER TYPES OF DISC DRIVE INDEX SENSOR
Above, a few manufacturers use a opto-electronic detection method.
This requires having a reflective patch and infra-red emitter/detector unit.
Above, I've only seen this once, a low cost method, using a small inductor
This will have a small amount of current induced as the magnet passes.