Hall Effect Magnetic Switch

Pierre Rondel
08/11/2009

Everybody knows that one of the main points of failure in the power supply in a RC sailplane is the switch. Most of the standard switches (if not all) dedicated to our hobby are average or bad quality. In addition they are usually big and not easy to install as soon as you have limited space like a HLG/F3K, or a F3X plane.

The HEM switch (Hall Effect Magnetic) from shop.soudez.be try to answer these requirements that are: offer a reliable and easy to use switch, in a very small size/weight, but still able to provide good power.

 

 

According to Wikipedia, Edwin Hall discovered this effect in 1879 which relies on the principle of the Lorentz force. When an electron moves along a direction perpendicular to an applied magnetic field, it experiences a force acting normal to both directions and moves in response to this force and the force effected by the internal electric field. The current which is created by the proximity of the magnet is used to activate deactivate the switch (in other words, switch on, switch off).

I have already seen such device for aeromodelling, but they are reserved/specialized for big plane and are pretty big.

Here we are talking about a tiny switch that is 20 x 8 x 5 mm only, less than 5 grams, but given for a steady state current of 5A which is more than enough for most of airplane/sailplane applications. Ideal for a HLG/F3K competition sailplanes where the battery capacity is poor, so where you need to save lifetime.

The size and reasonnable price has been obtain by doing a trade off: the switch is not protected against short cuts and polarity inversion.

The video below has been done at home and show how it works. I have soldered a JST plug because I will install the switch in my second Weasel. You can also suppress the battery side connector and solder directly the switch to the battery and add a charge connector in paralell.

When switched-on, a strong blue light indicates that the switch is ON, and the light can be seen through a fuselage or a canopy. What is very convenient is that if the switch is well position in the fuselage, you don't have to open the canopy to switch on the plane !

Hall Effect Magnetic Switch from Pierre Rondel on Vimeo.

But there is a but ;) don't loose the magnet which is very small. I advise you to glue or attach the magnet to a key ring or a piece of wood with bright colors. Hopefully, it works also with other magnets. The stronger is the magnet, the greater is the activation distance.

 

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