BLDC Replacement and Failure Analysis

A project log for TrillSat

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Lee DjavaherianLee Djavaherian 04/23/2018 at 03:510 Comments

I purchased an old, used Lite-On LDW-411S DVD+-RW drive (manufactured in 2003) that someone was selling on eBay and removed the BLDC motor to replace the one that I burned out a few weeks ago due to the chip lock-up/stall issue mentioned in my earlier log entry.  One of the problems of re-purposing old parts, however, is that drop-in replacements are harder to find (but I never expected to burn out my first one!).  Holes have been drilled for Gyrofan mounting, and small nuts have been epoxied behind the holes for easy assembly to the Gyrofan wheel.  I also had to be careful to ensure that the metal shavings from one of the holes that I drilled in the metal board (to widen it) didn't enter the motor, so I taped up the motor before drilling the holes. 

This time around, though, I decided to de-solder the ZIF ribbon-cable connector from the drive's circuit board and will use this, in place of direct soldering, to more easily and quickly disconnect or replace the motor in the future.

I tend to avoid analysis, deferring to logical deduction, but this was a good opportunity to see exactly what kind of motor I am dealing with, as there are many different types of BLDCs.  As you can see, it has 9 stator coils and the heat melted the plastic around the coils, wedging it against the magnetic rotor.

I had to clear out a lot of the wiring on Circuit Board C to remove the old BLDC and will be more careful next time to wire around the BLDC to prevent its removal from being obstructed.  The heat from stalling out the old motor actually caused the black printing to melt onto the white PETG gondola backplane.

Once the new BLDC is in place, I plan to get some video of both of the motors (the BLDC and the brushed DC screwdriver motor) under PWM control.  Then I'll start a pass through my Python, C, Lua, and OpenSCAD source code to get a version ready for open-source release.  Currently, my code has a lot of hard-coded customizations which first need to be generalized.