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hall effect switch

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boyabs2001

New Member
hi,

Can anybody tell me where to find hall effect switch from junk electronic appliances. I cant find it in supply stores in my place.

thanks, boyabs
 

Nigel Goodwin

Super Moderator
Most Helpful Member
boyabs2001 said:
hi,

Can anybody tell me where to find hall effect switch from junk electronic appliances. I cant find it in supply stores in my place.

thanks, boyabs

You can find them in most floppy drives, VCR's also use them - sometimes as reel sensors, but if not the capstan and drum motors (DC brushless motors) usually have three each.
 

john1

Active Member
Hi Nigel,

thats interesting,
i didn't know they were there.
could you elaborate on that a bit,
so that i could recognise them,

Cheers, John :)
 

Nigel Goodwin

Super Moderator
Most Helpful Member
john1 said:
Hi Nigel,

thats interesting,
i didn't know they were there.
could you elaborate on that a bit,
so that i could recognise them,

Cheers, John :)

To use a VCR capstan motor as an example, if you remove one from a VCR there is a large flywheel on the bottom, and the capstan sticking up through a bearing at the top.

They are usually held together simply by a circlip on the capstan at the top side of the lower bearing. Remove the circlip and pull the flywheel downwards, sliding the capstan out of the bearings - it takes a little force, as the flywheel is a magnet and trys to hold on.

Once that's out of the way there's a PCB underneath, with individual 'piles' of driver coils around the outside. Also on the PCB are a number (usually 3 or so) hall effect devices - they look like tiny black transistors, but with more wires.

These motors are known as 'DC brushless motors', a conventional brushes motor uses the brushes to switch different coils in to circuit to give rotation - in these motors the coils are switched by transistors, but the circuit needs someway of knowing whereabouts the rotor is to switch the coils at the correct time - that's what the hall effect sensors do.
 

Sebi

Active Member
You can also canibalized a bipolar hall-sensor from damaged PC-fan.
The bipolar hall is very interesting thing: with magnet nord-pole switch on, and south-pole switch off.
 

boyabs2001

New Member
Hi nigel,

Thanks a lot for your info. on where to get hall effect switch from
junk floppy disc driver. I found three inside, but my problem is, it has four legs. I dont know where to connect the +,ground, and out wires which are common on three legged hall effect i.c.


boyabs
 

Nigel Goodwin

Super Moderator
Most Helpful Member
boyabs2001 said:
Thanks a lot for your info. on where to get hall effect switch from
junk floppy disc driver. I found three inside, but my problem is, it has four legs. I dont know where to connect the +,ground, and out wires which are common on three legged hall effect i.c.

Have a look at http://www.cybench.co.uk/salv/hall/hall2.htm, which might help you, although it only shows three pin ones. Try following the circuit on the old drive to see what goes where.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Hope this helps, I managed to find a circuit diagram for an old Hitachi VCR capstan motor - it shows the three 4 pin hall effect sensors. It looks like the outputs require feeding into a differential amplifier.
 

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