Reverse engineering a three phase brushless motor fan speed controller - Page 1
Forum section: electronics / projects

author: plantgrower
author_rank: Contributor
timestamp: August 28, 2015, 01:30:21 am
content: I wish to reverse engineer the controller for this 12 pole, 3 phase brushless motor fanhttp://www.hyper-fans.com/shop/bybrand/hyper-fan/hyper-fanconytoller[url=http://www.hyper-fans.com/shop/bybrand/hyper-fan/hyper-fan-speed-controller-and-extension-cable]http://www.hyper-fans.com/shop/bybrand/hyper-fan/hyper-fan-speed-controller-and-extension-cableThe fan can be controlled between 35-100% of output. When the controller is removed, the fan goes to 100%.Any ideas on what the fan controller is doing to control the fan, PWM or something else ?I don't yet own one of these fans.Would a Rigol 1054z be of any use in this situation ?What connector is the fan using ?[url=http://i.ebayimg.com/00/s/MTEwMlgxNjAw/z/FpkAAOSw8d9UxsJq/]http://i.ebayimg.com/00/s/MTEwMlgxNjAw/z/FpkAAOSw8d9UxsJq/$_57.JPG

author: free_electron
author_rank: Super Contributor
timestamp: August 28, 2015, 01:46:27 am
content: probably simple phase chopping

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 28, 2015, 03:32:05 am
content: If it's anything like the common variable speed Delta fans, there's a full blown VFD inside with a DSP driving it.

author: jaxbird
author_rank: Frequent Contributor
timestamp: August 28, 2015, 06:12:49 pm
content: The pic16f178x does 3 phase in hardware, you just need to confirgure it and buffer the outputs correctly.It'll only set you back about $2 or so.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 28, 2015, 11:33:09 pm
content: The speed controller looks like an expensive 10k potentiometer at the control signal of the internal controller chip.

author: plantgrower
author_rank: Contributor
timestamp: September 03, 2015, 11:56:13 am
content: Quote from: Jeroen3 on August 28, 2015, 11:33:09 pmAre there any guides on how to reverse engineer the signal they are sending?

author: Jeroen3
author_rank: Super Contributor
timestamp: September 03, 2015, 12:20:35 pm
content: Guides? Most industrial control thingys with potentiometers use a current loop or a potentiometer as small voltage s4etpoint.One leg to +10, +24 or Supply positive. One leg to GND or Supply negative. And one leg to Analog in.But, you'd need to tear it down to know for sure that it is an potentiometer in a fancy box.

author: scrat
author_rank: Frequent Contributor
timestamp: September 03, 2015, 12:57:46 pm
content: The motor is a permanent magnet brushless motor with sinusoidal or trapezoidal back-EMF.There is some confusion about the terms, however cheap permanent magnet brushless motors are often called "Brushless DC" (BLDC), which is also the way they are controlled.The simplest control method is brushless DC, where two phases are conducting at each time, resulting in a phase current which is a squared + -> zero -> - pattern. The commutation between phases is synchronized with rotor position, and the right instant for commutation is usually estimated by reading the voltage (back-EMF) on the non-conducting phase.A rough speed regulation can be done simply imposing a certain PWM duty-cycle when the phase is conducting.This kind of control requires a 3-phase inverter and a simple microcontroller capable of generating 3 complementary PWM signals (as someone already said).At zero or low speed, commutation instant cannot be detected by means of back-EMF, so an open-loop arbitrary commutation is imposed (with a high current, and then with low efficiency), relying on the fact that the rotor will align to the phase having positive current. This could explain why speed is limited to >35%.

author: nowlan
author_rank: Frequent Contributor
timestamp: September 03, 2015, 02:02:52 pm
content: I would have thought it was a simple triac controller, like the normal speed controllers everyone else uses.http://www.harborfreight.com/router-speed-control-43060.html^ clearly its not.chopperhttp://www.freescale.com/training/classroom-training-events/motor-tutorial/phase-angle-control:WBT_MOTORPACTUT_WP3 phase pwmhttp://www.freescale.com/training/classroom-training-events/motor-tutorial/pulse-width-modulation:WBT_MOTORPWMTUT_WPDoes the fan not come with the controller? The fan is the newer EC fans vs typical AC fans. You wont be able to use the controller on them.My fishtanks MP40 pump has 3 phase freescale chip inside. Freescale have a lot of good documentation explaining how to drive chips + motors.

author: plantgrower
author_rank: Contributor
timestamp: September 07, 2015, 08:32:35 am
content: Quote from: scrat on September 03, 2015, 12:57:46 pmAccording to video reviews for this fan the 120v versions of this fan use approximately the following power :-The 6" version of this fan uses 12w @ 35% 48w @ 50% 55w @ 100%The 8" version of this fan uses 9w @ 35% 55w @ 50% 85w @ 100%The company that makes this fan is coming out with an automatic temperature controlled fan controller, if it is controlled by a potentiometer I presume that it would have to use a digital potentiometer. Which digital potentiometers would be adequate to control this fan ? Does anyone know of any examples or articles in using a digital potentiometer with a pid control algorithm ?