BLDC motors notes

How to debug new Brushless DC motor not working?

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I’m building an autonomous boat, for which I so far used this brushless motor powered by this drone ESC (both pictured above).

I now want to start using a more efficient motor, so I bought the 12V 4000RPM version of this motor (pictured below this message). I removed the old motor and connected up the new one. It gives the same beeping sounds when I calibrate it with the software, but after that, it doesn’t move at all. I use the exact same code and ESC setup with the new and the old motor. I tried the Go code I used for the other motor, and also tried some other example Python code with which the other motor also works great.

The wiring info of the new motor has 6 wires, as compared to the only 3 of the old motor. The wiring diagram of the new motor looks like this:

enter image description here

I connected it as follows:

  • the + of the ESC => red wire of the motor
  • the – of the ESC => black and the blue wire of the motor
  • the PWM signal of the ESC => yellow wire of the motor

I’m not sure if this is the correct way, but it’s the best I could come up with. I’m not sure whther the -/minus of the ESC should also be connected to the blue wire, so I tried it both connected and disconnected. But none of my attempts make the motor spin.

And from here I’m kinda lost. Seeing that I’m more of a software guy than an electronics guy I don’t really know how to debug such a hardware problem.

Could anybody give me some pointers on what the problem might be, and more importantly, how you go about debugging something like this? All tips are welcome!

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dcdc-motorbrushless-dc-motormotor-controllercalibrationshareedit  follow  flag asked Aug 4 at 14:36kramer6539377 silver badges1818 bronze badges

  • 1The instructions show a 10K pot on green,yellow,blue. I would suggest trying that : the pot should provide speed control. (with Red and Black to the PSU, and leave grey open or grounded to change direction). – Brian Drummond Aug 4 at 16:01 

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2 Answers



How to troubleshoot a BLDC motor?

bldc motor


Part A – TLDR

All my life I have been playing with toy DC motors, and I know them very well. However I have almost zero knowledge and experience on BLDC motors. I know that drones use BLDC motors, but actually I never owned any RC toys in my life, not to mention RC drones.

I also know quite a lot about 5V/12V regulated power supplies for toy motors, but I don’t know what is ESC, and I have never seen the real ESC thing in my life.

I need to introduce my sub newbie knowledge and experience on BLDC motor because I must warn the experienced RC guys that I am ignorant in RC, so bear with me talking stupid RC stuff. RC Ninjas can skip the following parts basic parts and start with the real BLDC thing.

But I would appreciate it very much if anyone can point out my misunderstanding on RC, ESC, and BLDC, so I can make corrections ASAP, before letting EE SE losing too much face, …

Part B – Googling and Wikiing on BLDC Motoers

/ to continue, …


(1) 38SRZ-S BLDC Motor 12V/24V 2000/3000/4000/5000 rpms with built in drive for DIY US40 – AliExpress

/ to continue, …

End of answershareeditdeleteflag answered 1 min agotlfong0162833 silver badges66 bronze badgesadd a comment-1

Your new motor is advertised as having a Built-in Drive hence it is not suitable for use with your ESC.

It’s possible you could rip out the internal driver and substitute yours, or learn to operate the internal driver (it probably comes from an industrial control tradition, not the 1-2 millisecond pulse of the RC hobby world), but questions on the usage of products (especially products with little documentation) are not on topic here.shareedit  follow  flag answered Aug 4 at 14:43Chris Stratton27.1k33 gold badges3232 silver badges7676 bronze badges

  • Do you mean to say that the motor has a built-in ESC? So theoretically I would need to add a PWM signal directly to yellow line of the motor? – kramer65 Aug 4 at 14:56 
  • Both the circuit in the motor and your ESC are brushless motor drivers. It is rather unlikely however that the driver in industrial motor system you bought wants the same signal that your RC hobby ESC does, as it comes from an entirely different tradition of application. You’ll have to figure out what it does want and devise a way to create that… if in fact the new motor system is suitable at all. – Chris Stratton Aug 4 at 15:04 
  • Ok great. I’m learning a lot here. And with “figure out what it wants” I guess you mean to say what kind of PWM signals it needs? I will of course ask the seller for generic documentation, but do you have any specific questions which I might ask them? – kramer65 Aug 4 at 15:20
  • What you need is a data sheet, not a connection diagram. A drawing of a waveform would help. But really, it is beyond obvious from the page that supplier is not a good place to be shopping unless you have enough domain knowledge to recognize exactly what they are offering and that it fits your need. You probably want to stick to RC hobby suppliers with familiar offerings. – Chris Stratton Aug 4 at 15:22 
  • You might be right, but for now I already have this motor, so I might as well try to get it going.. 🙂 I’ll ask the seller whether he has a data sheet and a drawing of a waveform. – kramer65 Aug 4 at 15:29
  • 1Ok, I got a reply from the seller. They say they bought these motors from a company who went bankrupt so they have no information on it.. 😮 So yeah. No info whatsoever. I know this is not really the place for this, but would you have any tips on how to proceed with this thing? Do I disassemble it? Do I start throwing random PWM values at it? What would you do in this case? Do you maybe know any other forums where I could ask about this? – kramer65 Aug 5 at 20:32
  • @kramer65, OMG, what do you mean by (1) “I know this is not really the place for this, …” and, then you said: (2) “Do you maybe know any other forums where I could ask about this?” I always thought that this is the only place you can get the best pro advice, also I do know a couple of other forums who give tips to newbies. One piece of good advice from those forums: (a) Just learn it, (b) Just do it, ie learning by doing it. Let show you how to learn it and doing it. I have years playing with DC brush motors, but almost zero experience with brushless dc motors (BLDC), / to continue, … – tlfong01 39 mins ago   
  • I must confess that all my life I never own or play with any RC toys. Now everybody is playing with RC drones, but I never own any. I know the drones are driven by BLDC motors. I have bought a couple of BLDC motors but never serious started learning the basics. Now it is another gloomy Sunday, perhaps the time has come to start BLDC. – tlfong01 35 mins ago   

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