TL;DR how not to blow up a BLDC motor or its driver and the hard-earned money I have spent on this kit while developing a firmware from scratch?

Story: I have never done any motor stuff before, but I am quite good with microcontrollers. To give motors a shot of experience I got myself this kit for a fair price (sensorless BLDC motor): enter image description here

I want to start from scratch and see if I can do as good as the original proprietary firmware (its only available in bin format). My question is:

Under which conditions the motor will get damaged (by a bad firmware) as I have heard that a badly placed debug point in code can release the magic smoke from the motor or driver. Or incorrect switching sequence of transitors, etc.

Can you please pinpoint the pitfalls that can lead to damage? So that me and future readers of this question can thank you!

Update (1) Suggest a lamp in series with supply power. Is this the case? enter image description here

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    \$\begingroup\$ Read the data sheets carefully and respect ESD and shoot thru failures. Current limiting should exist for locked rotor from Vcc/DCR currents. Start current is 10x rated current. so choose supply properly with decoupling. You will need an acceleration ramp to match your requirements for velocity and stability. \$\endgroup\$ – Tony Stewart EE75 Oct 11 '17 at 22:40
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    \$\begingroup\$ Also be sure to disconnect the power source during each code upload. \$\endgroup\$ – Todor Simeonov Oct 12 '17 at 7:51
  • \$\begingroup\$ @TonyStewart.EEsince'75 What is DCR? \$\endgroup\$ – Sean87 Oct 12 '17 at 12:43

One thing I have done in BLDC motor driver development is to put a suitable incandescent lamp in series with the bridge power supply. If the light comes on bright it just saved you a set of transistors.

Of course you are going to follow proper code development techniques to make the BLDC drive logic as independent as possible of the rest of your program, test it in simulation and with drive current limited, and ensure that everything looks wonderful on your multichannel scope before trying to drive a motor.

And maybe you should make sure you have a good desoldering tool and a few sets of replacement power components on hand, just in case.

  • \$\begingroup\$ Thanks for the info. My motor is sensorless and I think I need to have the motor connected to see the BEMF to decide when is the right time to switch a specific transistor pair. In that case, how can I use the scope without having the motor connected? \$\endgroup\$ – Sean87 Oct 12 '17 at 12:15
  • \$\begingroup\$ Can you please also check my update, is that what you mean by a lamp in series? \$\endgroup\$ – Sean87 Oct 12 '17 at 12:41
  • \$\begingroup\$ Yes, that's what I mean. There are possibly complications if the transistors don't turn on fully, so it's impossible to say for sure if that will work without thorough analysis, but that's the basic idea. \$\endgroup\$ – Spehro Pefhany Oct 13 '17 at 4:26
  • \$\begingroup\$ It's more complex with a sensorless motor, however the startup usually operates as an open-loop variable frequency drive and you can at least make sure that operates properly. \$\endgroup\$ – Spehro Pefhany Oct 13 '17 at 4:27

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