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Hey guys,

I'm new to this site, and am a university student studying Electrical and Electronics engineering. I just completed a design project controlling a BLDC motor (pretty low powered at 60V, and giving output rpm of about 6000rpm). Now I had an idea where instead of using a single BLDCM for an application, would it make sense to put two identical BLDCMs on the same shaft, in order to give double the output torque? I would operate the two using the same drive as I would use for one, but I'm still unsure of how to take into account a lot of my efficiency calculations. I have a feeling that this would just draw double the power (if not, then only provide half the output power to each motor).

Please help me out. I need some answers ASAP for an important project.

Cheers

BLDC motor investigation by Raag90Raag90, 10 Mar 2011 10:30

Dear Fernando,
I rather call you the GURU.You had done a good job in starting this kind of site. As beginners like me need such kind of explanation and your site and work proves to be good.Guru i am also working on BLDC ESC.I had undergone many application note from atmel and microchip, Even some thesis.But this site had given me some confidence to start with.I had designed 40A 6 mosfet power stage and back sensing circuits.I want to participate in your work.I will post my schematic of power stage and back emf sensing circuits (EAGLE software is been used).Many methods are been explain for sensing the initial position of rotor as it is highly recommend for good start-up of motor.One of your video posted in the site also shows that you have completed this task of sensing rotor.But you have not given any information about how you did.So guru can you please elaborate about how to sense rotor position by pulse injection method.

Regards,
dudedevil

The system worked quiet well with little motors but with bigger motors it failed the correct phase detection.
I need stronger power supplies, hardware that can handle bigger currents, and to test different solutions to achieve a good phase detection.
I work with software and I don't have in my home enough hardware resources. And I am not prepared to project new hardware because it's not my main field. I am an electrical engineer and I can understand the hardware the others do but it is not enough to project new hardware and I have no time to spend with hardware.
I am waiting for a friend that works with hardware, and lives in Lisbon near me, to continue the project.

Re: Gattuso presentation by RSilvaRSilva, 01 Dec 2009 21:47

what kind of hardware?

Re: Gattuso presentation by GattusoGattuso, 30 Nov 2009 10:21

You are welcome.
This project was stopped waiting for hardware suport.

Re: Gattuso presentation by RSilvaRSilva, 29 Nov 2009 17:22

I thought rs232 was good because it's easy to interface with the microcontroller and the zigbee (XBee-PRO, etc) is affordable.
Now the project is stopped with need of hardware support. The complex problem is the motor control and not the communications link.

Re: Hello from JimDJr by RSilvaRSilva, 29 Nov 2009 17:21

hi there

my name is Filipe Salgado, but i use the Gattuso alias ;)
i'm studying Electronis engeneering, and on my 4th year project get involved with brushless motors and ESC, and discovered this wonderfull source of information!!!!
thanks mr Silva!!

from now on i'll keep in touch to get some extra information, and maybe post what i have discovered…

best regards!!!

Gattuso presentation by GattusoGattuso, 18 Nov 2009 23:17

What is the thread ratio on the screw gears?

Re: BLDC motor load performance by JimDJrJimDJr, 07 Nov 2009 19:18

Hello my name is Jim. I have been working in electronics for 33 years an I have been playing with RC models for a while as a hobby. Recently I have been looking into ways to make money with Remote Control systems. I also have been programming in various langauges since the 70s again mostly as a hobby. I don't know if I can help but I always have an opinion. Why RS232 and not USB or Blue tooth?

Jim,

Hello from JimDJr by JimDJrJimDJr, 07 Nov 2009 19:16
Re: AVR based ESC with other microcontroller by saeed talebian (guest), 01 Sep 2009 09:28

Hi,
I am using Sensored BLDC motors for some robotic movements. I am driving my motors using motor drivers. I am using ball screw mechanism for lifting a pedal up and down. On the pedal, there will be always a very high load, placed on it.

Now, my motor can lift up the pedal with my desired speed accurately but while going downward, the pedal just goes down freely overcoming the output speed of the motor.

Picture1.jpg

In summery I would like to say, when the motors are on downward rotation, they can’t hold the weight of the load and fail to conform to the desired downward velocity; instead they just let the pedal goes down freely until it reaches the lower threshold.

If you have any questions please let me know

thanks in advance

BLDC motor load performance by tirupotitirupoti, 08 May 2009 13:27

Hi,
First, I wanted to congratulate you on the great information and work you have done related to BLDC in this website.
I have bought Suppo 18A ESC which is AVR based ESC(Electronic speed controller). I would like to have a PWM signal generated by LPC2148(ARM based microcontroller). This PWM signal will be the input for the 18A ESC which will drive the motor.
I had a few questions:
Is it possible to drive the AVR based ESC and the motor with an external PWM signal from the LPC2148.
The PWM signal from the LPC2148 is a 3.3V signal. Will the AVR based ESC work with this signal or I need to have a 5V signal.
If the PWM signal should be 5V, do you know how to make the 3.3V signal amplified to 5V.
If the LPC2148 has 4 PWM generators can I link them to 4 ESC's to drive 4 motors.

Hi,
First, I wanted to congratulate you on the great information and work you have done related to BLDC in this website.
I have bought Suppo 18A ESC which is AVR based ESC(Electronic speed controller). I would like to have a PWM signal generated by LPC2148(ARM based microcontroller). This PWM signal will be the input for the 18A ESC which will drive the motor.
I had a few questions:
Is it possible to drive the AVR based ESC and the motor with an external PWM signal from the LPC2148.
The PWM signal from the LPC2148 is a 3.3V signal. Will the AVR based ESC work with this signal or I need to have a 5V signal.
If the PWM signal should be 5V, do you know how to make the 3.3V signal amplified to 5V.
If the LPC2148 has 4 PWM generators can I link them to 4 ESC's to drive 4 motors.
Thank you and have a great day.

Sumit Bhatnagar

I sent you a message. Try it.

Re: Hello from Ekawahyu Susilo by RSilvaRSilva, 10 May 2008 23:08

That would be great! I managed to start small motor using stepping mode for 5-6 cycles and then continue to BEMF. But stepping mode doesn't actually work for bigger motor as from HDD. But I could use other method to drive it anyway, so I had no problem at startup at all. Now I just need to make it general for every motor driving.

Please let me know when you have already made and allocated pages for me, thanks! I hope we could share knowledge here to everyone.

No. I will use only ATMEL in this project.
If someone else want to use other micro controller I will help if possible and I let him create a page in this site
Fernando.

Re: The startup by RSilvaRSilva, 15 Mar 2008 14:55

hi there…

i am new user on this forum. i would like to know if u all have a source code to control bldc motor using tms320f2812. i am using code composer studio.plz…

Re: The startup by orchidorchid, 05 Mar 2008 07:44

The software (startpos.asm) is tuned for the hardware I use now so you must tune the software for your hardware. There is at least two important variables: how much to wait for the ADC reading (after the beginning of the pulse) and the voltage level you get at the ADC (with this hardware less than 5V and high enough to obtain good sensitivity).
So if you use a different hardware you can not just copy the program. How can I tune for my hardware without expensive equipment? With the Visual Basic program (startpos.exe) that shows what is happening inside the ESC.

1. I measure inductance changes with the ADC (voltages)
2. I have to saturate the motor with the current pulses to obtain a unique position for the 360 electric degrees. Otherwise I get the same value for the measures 1 and 4, 2 and 5, and 3 and 6. Try higher voltages if needed.
Note: Measure 1 is A+B- and measure 4 is B+A-, they are obtained at the C terminal and with opposite voltages between A and B. Why this sequence? To keep the rotor stopped with opposite magnetic fields. After the pulse, how much time I am waiting for the ADC reading? Aprox. 270 micro seconds (27*10 us).
3. I get the response curves of the motor and I plot an Excel graph. See the Excel file "ADC Values" at http://bldc.wikidot.com/downloads.

If the curves are OK we can use this motor/ESC couple.

Re: The startup by RSilvaRSilva, 20 Feb 2008 22:55

I am going to copy parts of e-mails I received and I sent, all about the startup.

Subject: About rotor position detection

Hello,

I tried to understand yout algorithm to detect the start position of the rotor. But its not easy.

It would be very nice, if you can call some sentences about the prinziple and some sentences to describe the algorithm, so that I can easier read the program code.

With best regard

My answer (with a few modifications):

It’s not easy to explain.

I tried to use the inductance measurement that is widely talked. You can see the links on that page and on http://bldc.wikidot.com/p-esc-motor.

I didn’t made all the theoretical calculus because this is not a Thèse. This is a hobby and I am alone in this project.

I am detecting the point where there is more inductance and the point where there is less inductance.

To study this you can see the program startposition. The numbers you see on the figure correspond to voltages you get (see the ADC) at the 6 different situations.

The program begins with the RESET Handler (RESET:). Than it initialize several systems and begins an infinite loop (Loop1:).

TEST1 is the basis:

rcall Read_ADC_Str1
sts ADCPos_Ini_I+1, temp2

delay n

rcall Read_ADC_Str4
sts ADCPos_Ini_I+4, temp2

delay n

rcall Read_ADC_Str2
sts ADCPos_Ini_I+2, temp2

delay n

rcall Read_ADC_Str5
sts ADCPos_Ini_I+5, temp2

delay n

rcall Read_ADC_Str3
sts ADCPos_Ini_I+3, temp2

delay n

rcall Read_ADC_Str6
sts ADCPos_Ini_I+6, temp2

delay n

sts is used to keep the values in SRAM.

I have a lot of work to do and not enough time. This Wiki site was created to get a community working on this project.

Alone I have no time to big explanations. Neither the disposition at least for now. Sorry.

Use the forum, maybe someone helps.

Regards

Fernando

Re: The startup by RSilvaRSilva, 20 Feb 2008 22:15

This thread is about the ESC (Electronic Speed Control) Hardware and similar or more generic subjects. Please see BLDC Motors/The Startup in this forum intended to be almost only about the startup topic.

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