HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 23, 2013, 02:32 PM
Registered User
Joined Oct 2012
33 Posts
Discussion
Securing hall effect sensors

Hi Everyone,

I'm working on building a BLDC hub motor for a school project. The motors are sensored using three small hall effect sensors that go in between the stator teeth. I'm sure anyone familiar with BLDC sensored motors knows what I'm talking about.

My concern is however just wedging the sensors in there. I would like them to be secured in position so they don't come loose during operation. My question is then what would be the best/most commonly used way to secure these sensors?

I was considering using basic hot glue but am not sure if this is a good idea given their melting point. I also don't know if and how hot glue interacts with magnetic fields, since this would be quite detrimental to the motor operation.

Any suggestions are highly appreciated.
a_man87 is offline Find More Posts by a_man87
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 27, 2013, 07:28 PM
Registered User
Joined Oct 2012
33 Posts
bump
a_man87 is offline Find More Posts by a_man87
Reply With Quote
Old Jan 27, 2013, 07:39 PM
Always comPLANEing
Chophop's Avatar
Pleasant Valley Modelport
Joined Sep 2006
8,262 Posts
Common epoxy should work, Google for some higher temperature types. The epoxy shouldn't interfere except for most JB Weld formulas which do have iron.
Chophop is offline Find More Posts by Chophop
Reply With Quote
Old Jan 28, 2013, 08:54 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,320 Posts
The reason that you are not getting much of a response on your question is that virtually all of the motors currently used in electric RC for flying are sensorless. In the five or six years I've been playing with brushless motors (all outrunners), I have yet to have handled or seen a single sensored motor.

They are a little bit more used in electric cars because of the desire there for smoother starting and reversing. With propellers, having the start up sensing done by the ESC is virtually imperceptible and it also simplifies things.

You might be able to find more info on sensors on the RC electric car forums.

Jack
jackerbes is offline Find More Posts by jackerbes
RCG Plus Member
Old Jan 28, 2013, 09:00 AM
Registered User
Joined Oct 2012
33 Posts
thanks
a_man87 is offline Find More Posts by a_man87
Reply With Quote
Old Jan 28, 2013, 10:47 AM
Registered User
Joined Oct 2012
33 Posts
So after some research here is what I found for anyone interested.

You can get hot glue for a wide range of temperatures. Typically these are around 70C, so roughly the same rating as the magnets and hence if you are exceeding this temp, then you have more serious issues than just some melted glue. However you can get higher temperature rated glue as well just to be on the safe side.

As for magnetic characteristics, typical hot glue does not contain any magnetic materials and hence does not affect the magnetic characteristics. It is even suited for applying directly to magnet wire, provided it doesn't get too hot. Most hot glues are made of non corrosive thermoplastic but this is something that should be confirmed as corrosive material will wreck havoc to the magnet wire's insulation.
a_man87 is offline Find More Posts by a_man87
Last edited by a_man87; Jan 28, 2013 at 11:50 AM.
Reply With Quote
Old Jan 28, 2013, 12:46 PM
Always comPLANEing
Chophop's Avatar
Pleasant Valley Modelport
Joined Sep 2006
8,262 Posts
You would be best to use a motor rated for sensors. Sensorless motors, well cheap ones will not be ready to commutate at even intervals. The sensorless esc can manage that.
Chophop is offline Find More Posts by Chophop
Reply With Quote
Old Jan 28, 2013, 01:00 PM
Registered User
Joined Oct 2012
33 Posts
These are actually for a set of 4 motors that I am building to be incorporated into a pair of electric rollerblades for a school project. The motors are being built completely from scratch, except for the laminated stators which I purchased.

My understanding is that sensored and sensorless BLDC motors are essentially the exact same. One just has hall effect sensors stuck between 3 of the stator poles. Therefore a sensored motor can always be operated as a sensorless motor without any issues. The difference between the two is only the type of ESC that needs to be used.

I am however new to the whole motor building scene so please let me know if I am mistaken.
a_man87 is offline Find More Posts by a_man87
Reply With Quote
Old Jan 28, 2013, 02:40 PM
Always comPLANEing
Chophop's Avatar
Pleasant Valley Modelport
Joined Sep 2006
8,262 Posts
Differences between windings and magnet spacing can affect the commutation point. Cheap or poorly built motors will not have the same mechanically located 0 point at each pole cycle. Motors properly built for sensors, should have better symmetry of the switch point.
Chophop is offline Find More Posts by Chophop
Last edited by Chophop; Jan 29, 2013 at 07:18 PM. Reason: Added some detail
Reply With Quote
Old Jan 29, 2013, 06:19 PM
Registered User
Joined Dec 2012
14 Posts
in sensorless ESC the controller at start up try to spin the motor in a random direction and start listening on the wires for what's going on.
The controller can detect form back EMF how the rotor is relatively the stator , after this first step now the controller is aware of the motor position and can start controlling it in the sensorless way ( it use the unused phase wire as a sensor)

this trik work only if the motor can spin freely ( air propeller or water propeller) or if there is some other force starting the motr ( e-bike) , if you need a motor able to start from stop under load ( think at a car starting uphill) then you need a sensorer motor.


Sensored motor are also more efficient on load variation because the controller can adjust the advance by checking the effective magnetic field and not having a fixed timing
Athlon is offline Find More Posts by Athlon
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Joystick use a Rotary Hall effect sensor. lazy-b DIY Electronics 8 Jul 27, 2012 06:46 PM
Discussion Hall effect RPM sensor kitedan Eagle Tree Systems 4 Jan 27, 2010 01:15 AM
Discussion Interfacing a hall-effect sensor pserve DIY Electronics 0 May 24, 2006 12:46 PM