Brushless motor??? - Page 1
Forum section: electronics / general

author: cybertronicify
author_rank: Regular Contributor
timestamp: August 12, 2014, 06:30:11 pm
content: Hey guys!What is the cheapest way to drive a brushless motor. Right now i have 3 mosfets and a PIC. But i want to cut it down to say one IC and some passives.Like this:http://www.ebay.com/itm/EMAX-CF2822-1200KV-Outrunner-Brushless-Motor-for-RC-Aircraft-Airplane-Helicopter-/281181421209?pt=Radio_Control_Parts_Accessories&hash=item4177b7fe99

author: SirNick
author_rank: Frequent Contributor
timestamp: August 12, 2014, 06:43:11 pm
content: What else do you need it to do? Speed control? Startup sequencing? Current monitoring? And at what voltage and current?

author: Zbig
author_rank: Frequent Contributor
timestamp: August 12, 2014, 06:45:53 pm
content: There are many dedicated BLDC motor controller ICs out there. Driving this kind of motor properly is quite involved because of the lack of commutator. You have to be able to sense the current position of the rotor accurately, either with the help of a Hall effect sensor or (as is the case with small R/C hobby motors) by sensing the back-EMF. You could be able to make the motor spin just by the means of "blind commutation" but you won't get anywhere near its potential performance this way.EDIT:Most probably you won't be able to do this any cheaper than just getting a ready-made ESC from HobbyKing and driving it with PWM signal.

author: retrolefty
author_rank: Super Contributor
timestamp: August 12, 2014, 06:52:19 pm
content: In the R/C world the motor controller for such motors are called ESC (electronic speed controller) and allow the motor to be controlled as if it is a standard hobby servo. That same seller has several ESCs listed among is offerings. They are by far the least expensive means to drive that brushless motor.

author: wraper
author_rank: Unknown
timestamp: August 12, 2014, 07:22:35 pm
content: Quote from: Zbig on August 12, 2014, 06:45:53 pmYeah, no way you'll be able to beat their price. Only reason to DIY it is if you just like to make all yourself or need something specific.

author: vlad777
author_rank: Frequent Contributor
timestamp: August 12, 2014, 07:59:17 pm
content: I recently heard about this chip.MCP8024It is suppose to be sensorless bldc driver for triphase motors.By Microchip.

author: SirNick
author_rank: Frequent Contributor
timestamp: August 12, 2014, 09:24:13 pm
content: That MC part baffles me. After a cursory glance, I don't see how the uC is supposed to get the motor speed. The 8024 has PWM inputs meant tosetthe speed, and reads the back EMF from the motor, but doesn't seem to have any means of reporting this to the uC.Meanwhile, it doesn't look like it actually sequences the motor itself, but relies on the uC to implement lock, ramp, and run modes while blind. Why does it even go to the trouble of sensing EMF then, if it's just going to leave the uC in the dark anyway. Is that typical of motor controllers?

author: cybertronicify
author_rank: Regular Contributor
timestamp: August 12, 2014, 09:31:00 pm
content: Its just the most simplest turning. Making it spin full speed. This should work, prob cant beat any other DIY projects. haha 10 Amps 6 bucks not bad.http://www.ebay.com/itm/10A-Electronic-Speed-Controller-RC-ESC-BEC-For-RC-Helicopter-Brushless-Motor-S9-/390874121441?pt=Radio_Control_Parts_Accessories&hash=item5b01e9c4e1

author: rob77
author_rank: Super Contributor
timestamp: August 12, 2014, 10:06:18 pm
content: definitely buy an ESC - they're cheap. if you need better control, then you can hack it - reflash the MCU inside the ESC - google for BLHELI firmware (source code available) and of course buy an ESC with a reflashable MCU and compatible with BLHELI.easy way to get independent speed read-out would be to put a hall sensor in the proximity of the rotor (close to the exposed magnet ring in the rotor).