The one you have could be exchanged for a more up to
date one, even Radio Shack has them.
Here are excerpts from http://www.deja.com search for
Hall Effect switches;
Digikey carries Cherry, Micronas and Panasonic Hall
sensors. Also check Sprague (now Allegro/owned by
Sanken of Japan) http://www.allegromicro.com
They have 3 connections- +, gnd and output.
For more info, look for Allegro data. They make a
whole range of Hall devices, and their data sheets and
applications notes are excellent.
Try a web search. Be sure to use the term "Hall
Effect Switch" rather than simply "Hall Effect" (to
avoid the analog, magnetic field measurement type
devices).
Look for familiar names like "Microswitch" and other
well known keyboard suppliers, since they are the
quantity consumers of these devices and, for the
reason, may also be the key producers and suppliers to
the OEM market.
----------------------------
How a Hall Effect Switch (sensor) works;
A current flowing through a conductor passing through
a magnetic field encounters a force that pushes
perpendicular to the current and perpendicular to the
field (the force is determined by the cross product of
the two vectors).
This force acts on the current itself, and it is the
force that we use to do such things as make motors
spin. In this common context, the current is confined
within thin conductors (wires!).
In the Hall effect, you take a broad conductor and let
a current flow from one end to the other. If there is
a magnetic field perpendicular to the plane of the
conductor, it will push the current over to one side,
and this will give you a side-to-side voltage across
the conductor. This was discovered by Mr. Hall, hence
the name.
In a Hall effect sensor, you provide a constant
current between two terminals and the voltage is
measured across the other two terminals. I believe
that some hall effect sensors contain integrated
constant current sources; I know that some Hall effect
sensors have only three terminals, power, ground and
sense. The voltage from ground to sense is the Hall
effect voltage. Finally, some Hall effect sensors
include an amplifier, so that the sense output isn't a
tiny voltage linearly related to the field, but is
large and nonlinear. For example, there are Hall
effect sensors with TTL outputs that switch on when
the field exceeds some threshold and switch off when
the field falls below some other threshold -- the
built-in hysteresis is because there's a schmidt
trigger built into the output circuitry.
> Does it have polarity?
The basic 4-terminal Hall effect device, with no
on-board electronics, has no polarity. If there's a
built-in output amplifier or a built-in current
source, there will definitely be a polarity.
> Which manufacturer makes such a component?
Allegro semiconductor makes a large selection. They
have a web page, I think it's http://www.allegro.com
or something equally commonplace.
--- Robert <billc9@prysm.net> wrote:
> Hello All, I need help with understanding the
> schematic at John's website. Address is
> http://www.nidlink.com/~john1/idea.html
> Its the Adams type test motor for energy recovery.
> At the Hall switch 3020T in the schematic, there is
> 1,2,3 for connecting the wiring to the switch. The
> Hall 3020T switch is not available anymore. Its a
> magnetic type switch, but is 1 com?, 2,NC, 3, NO??
> Or is it set up completely different from that
> style. I need to change from a manual switch to this
> setup. The manual switch is taking a beating and
> very noisy. I have all the needed parts to build '
> this setup except the Hall switch. Will a 10 watt
> magnetic reed switch work? If so how should it be
> wired in? I can easily convert this using a
> different plastic washer with magnets secured to it,
> to activate the switch. I just dont want to burn
> every part on the board up by hooking it up wrong.
> Any help?? Regards, Robert
=====
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