Using The Hall Effect to Drive Brushless Motors

What makes brushless vibration motors long life? The clue’s in the title!

The precious metal brushes are typically the most common source of failure that limits the lifetime of normal DC motors. They are integral to the operation of our eccentric rotating mass vibration motors in the ‘Vibration Motor’ section of our Product Catalogue.

Whilst our recent Application Bulletin demonstrated our miniature vibrating motors are achieving an MTTF in the region of 1,500 – 2,000 hours some applications demand even longer performance.

So to improve life the solution seems simple, find a replacement for the brushes! This is actually quite complicated, the job of the brushes was to reverse the direction of the current through the internal metal windings (this ensures a constant direction of rotation of the shaft).

This is achieved by sensing the position of the internal windings and electrically changing the direction of the current at exactly the right time. To do this, we use the Hall Effect to calculate the position of the motor and change the drive signal accordingly. For more information on this, see Application Bulletin 018: Driving Brushless Vibration Motors.

Instead, with this blog post, we wanted to share an interesting infographic found on spingarage.com. Those interested in seeing exactly how the drive signal changes with the output from the Hall Effect sensors can study the image below.

Thankfully if you find the graphics confusing, you don’t really need to fully understand it. Our 910-101 has an integrated driver chip that handles the communication automatically, and we have a suggested circuit for the 912-101 that you can easily implement.

Of course, if you have any questions about brushless motors or how to drive them, please get in touch with us!