Hall effect sensors

Hi all

I have been looking at hall effect sensors instead of using potentiometers. As I understand it, you do away with direct contact to you controls and do not having to use gears etc.

Do you need to have a magnet to get a hall effect sensor to work or can you place the sensor close enough to a metal rod to get it working.

Reason I ask is my cyclic is connected to two horizontal rods that have a forward and backward movement of about 10cm.
The pedals are the same set up with about 12cm horizontal movement.

Anyone with any thoughts on hall effect sensors or using them ?

Cheers

Rhys

A Hall effect sensor like the Allegro A1301 produces a voltage output proportional to the strength of the magnetic field. So, yes, you need a magnet.

A Hall effect position sensor like the HRS100 incorporates a magnet in its construction. In fact, that particular model looks very much like a standard potentiometer, and can be substituted for a pot in some applications.

For some thoughts on applying a Hall effect sensor see the May 5 and March 25 entries on my site: http://www.mikesflightdeck.com/

Thanks Mike,
If I attach a magnet directly onto the horizontal rods, will that work? or is there another way to setup hall effect sensors for linear movement

Here is a picture of my control rod setup for the collective controls
http://i128.photobucket.com/albums/p178/hsvgto/rods.jpg

Rhys

Unfortunately, linear motion of a magnet near a Hall effect sensor does not result in voltage output that varies linearly. The magnetic field distribution around the magnet is simply too non-linear.

Linear position sensors based on the Hall effect do exist, but they incorporate a magnetic structure that directs the field so that the field strength seen by the Hall sensor does vary linearly with motion. Moving Magnet Technologies makes linear Hall position sensors. The company web site has some info on them http://www.movingmagnet.com/en/analo...e-measurement/

You could build something like this, but it would be expensive and difficult to find the proper material. You need a metal with high magnetic permeability and very low remanence. Permeability is the property which concentrates magnetic flux. Remanence is the degree to which a material becomes magnetized when exposed to a magnetic field. Materials with high permeability generally also have high remanence. High remanence in a sensor results in very high errors in the sensor output. High permeability/low remanence materials are generally nickel-steel alloys made by specialty firms.

A high quality slide potentiometer is a very workable solution in your application. If you prefer a non-contact solution, you could use an LVDT (linear variable differential transformer). LVDTs can be purchased through Ebay or made DIY.