View Full Version : Retrofitting sensors to sensorless motors

09-18-2008, 10:10 PM
I know this seems strange, but I was wondering if anyone ever looked into fitting hall sensors into a sensorless outrunner motor. I need a very high starting torque which so far has not been possible with sensorless controllers. The large sensored motors from Aveox and Ikarus are not available anymore, and the non-rc motors just are not made for high power in small lightweight packages.

PS: This is not for RC, but you guys are very knowledgeable so I figured why not ask.

09-19-2008, 06:27 AM
The trick wil be finding a controller that can make use of the hall sensors.

As far as I know none of the typical sensorless ones will be of any use - they just dont have the hardware or software to work that way.

Do you have access to any of the older Aveox units?

You might contact Pete at Model Electronics. He may have some old stuff laying around.

09-19-2008, 06:38 PM
I can either build my own sensored controllers (size and weight is not a major issue) or buy off the shelf units designed to run the motors on brushless motor scooters or e-bikes. You can also still buy the Maxcim controllers.

The problem is figuring the orientation of the hall sensors. I have some AXI 5330/18 motors that I am going to experiment with. The is sufficient room to mount hall sensors between the coil windings so they can sense the magnets rotation/position. I guess I will just have to go back to the books and figure out the positioning.

I also have some optical encoders that have simulated hall effect sensor outputs for using in driving brushless motors. These units need to be matched with the correct number of poles in the motor. The AXI motors are 12 pole and I am not sure if I can find matching sensors.

Bill Hawthorne
09-20-2008, 12:59 AM
Why don't you contact Tom at MaxCim...model motors arn't the only thing he is involved with...

09-24-2008, 05:28 AM
The brushless outrunner motors in CD-ROM drives use Hall sensors (see below). Perhaps you could learn something about orienting the Hall sensors by examining a CD-ROM motor.

- Jeff

09-24-2008, 05:15 PM
I have been looking at a few other brushless motors that I have. I have studied outside rotor motors from Ametek vacuums motors and from copier machines both of which are three phase and use hall sensors. The problem is the number of poles in the newer motors. I would think from my reading and observation all I have to do is place the three hall sensors inbetween three continuous poles. I would have to experiment to get the correct phasing but I have done that before.