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how to make a reed switch for sensing a magnet from 4 to 5inch distance? or a substitute with RF Answered

pls guide,
that i want to know the way to make a reed (in DC) have to sense a magnet from a distance of 4 to 5inches.
did small reed will act so ?? if a yes, then which specification have to look??

or did there any circuit or something for making it much more powerful??



use a hall-switch.

Ohh, the i am planning for some thing, let me share;

transmitter and a receiver (or a tag, but i don't know that tern exactly :( ), very small in size, power will be from button
batteries, also on the receiver, i have to fix one LED, when the
receiver finding the transmitter, this LED should ON on Transmitter..whn it is away, LED
will be off.

the distance is same, approximately 5 to 6 inch or so.

could u guide me pls??

seems this will be best for my purpose.

Hall Switch, let me find the differences among Haal effect switch and Reed Switch

Yea big magnet really big magnet.

If you tell us what you are trying to do we might be able to give you a better answer.


From 4 or 5 inches away even a HDD magnet has trouble moving the needle of a compass. The pulling force of a magnet drops off rather quick the further you get from it.

4 to 5 inches? A reed contact? Two words: No. Way.

4 to 5 Millimetres - yes. Twice/thrice that - possible, with a strong magnet.

What do you want to do? A magnetic field is just not strong enough.

use a harddrive magnet or any other super strong magnet of print one on this thing