T
Technology Guy
Guest
Is there such a thing as a magnetic switch or sensor that would sense
a magnet in the range of 12"-6" away?
a magnet in the range of 12"-6" away?
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Gareth Magennis
Guest
Look for Hall Effect sensors - 3 pin devices that either switch or give a
variable output in the presence of a magnetic field. The maximum range is
dependent on the srtrength of the magnet and the sensitivity of the device.
The variable output ones could be used in a comparator type circuit to give
greater maximum range than the fixed types.
Gareth.
"Technology Guy" <dotnet_vb_newbie@programmer.net> wrote in message
news:85e6327f.0411190556.6d51d4a4@posting.google.com...
variable output in the presence of a magnetic field. The maximum range is
dependent on the srtrength of the magnet and the sensitivity of the device.
The variable output ones could be used in a comparator type circuit to give
greater maximum range than the fixed types.
Gareth.
"Technology Guy" <dotnet_vb_newbie@programmer.net> wrote in message
news:85e6327f.0411190556.6d51d4a4@posting.google.com...
Is there such a thing as a magnetic switch or sensor that would sense
a magnet in the range of 12"-6" away?
D
Dave VanHorn
Guest
Reed switches can do this, but it's not easy.
You add a biasing magnet that brings it almost to the switch point.
You can also detect by pulsing a solenoid coil around the switch, till the
switch closes.
The on-time then tells you the strength and direction of the external field.
If it takes longer, the external field is opposing, shorter means it's
aiding.
You add a biasing magnet that brings it almost to the switch point.
You can also detect by pulsing a solenoid coil around the switch, till the
switch closes.
The on-time then tells you the strength and direction of the external field.
If it takes longer, the external field is opposing, shorter means it's
aiding.
W
Watson A.Name - \"Watt Su
Guest
"Technology Guy" <dotnet_vb_newbie@programmer.net> wrote in message
news:85e6327f.0411190556.6d51d4a4@posting.google.com...
Seriously. I've seen this with a set of foil plates glued to the
compass' glass face. The plates are part of a capacitive bridge. As
the needle moves, it unbalances the bridge. A similar arrangement can
also be used with a bubble level.
If you want to find out more about these kinds of sensors, try looking
for info on geotechnical stuff like earthquake and tilt sensors; and
also check the Amateur Scientist articles in Scientific American.
news:85e6327f.0411190556.6d51d4a4@posting.google.com...
It's called a compass.Is there such a thing as a magnetic switch or sensor that would sense
a magnet in the range of 12"-6" away?
Seriously. I've seen this with a set of foil plates glued to the
compass' glass face. The plates are part of a capacitive bridge. As
the needle moves, it unbalances the bridge. A similar arrangement can
also be used with a bubble level.
If you want to find out more about these kinds of sensors, try looking
for info on geotechnical stuff like earthquake and tilt sensors; and
also check the Amateur Scientist articles in Scientific American.
W
Watson A.Name - \"Watt Su
Guest
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:EZudnQQbiLpNNgPcRVn-uQ@comcast.com...
news:EZudnQQbiLpNNgPcRVn-uQ@comcast.com...
This kind of reminds me of the flux gate magnetometers.Reed switches can do this, but it's not easy.
You add a biasing magnet that brings it almost to the switch point.
You can also detect by pulsing a solenoid coil around the switch, till
the
switch closes.
The on-time then tells you the strength and direction of the external
field.
If it takes longer, the external field is opposing, shorter means it's
aiding.
D
Dave VanHorn
Guest
Kinda..This kind of reminds me of the flux gate magnetometers.
I did this years ago, as a demo of what a determined person could easily do
to defeat an alarm system. I built this, and some other goodies into a TV
remote case. This part was for locating magnetic switches in doors.
It also looked for IR beams, and ultrasonics, and some other things.