Dear Diary,
I got a bit bored today. As I was contemplating that it would be about time to clean up the workdesk my eye fell upon some harddisks that were waiting to be slaughtered. At that very moment a little lamp lit up inside my brain (light was pouring out of my ears).
[Start flashback] For the past 2-3 weeks I've been looking a bit into variable frequency drives for the lathe. Just 'for the fun of it' I'd like to drive the latest motorconversion (which is now a generator) as a motor too. And, I've been thinking more... For those who already have a 12-24-48Vdc system in their house but would like to operate their tools (lathe, drillpress), it might be an idea to use a motorconversion and a small VFD for 12-48Vdc. Especially the RC aircraft electro scene has some very nice 12Vdc 3-phase drives (70+ A...) to drive small 3 phase brushless motors. I was contemplating building one to drive the 500W conversion as motor, till my eye happened to fall upon the harddisks on the workbench... [end flashback]
Thinking... those harddisk motors are brushless 3 phase motors. So, somewhere on the board there must be a driver. Now, if I could hook up my motor to the drivers... and perhaps make RPM adjustable too...
So, took apart one of the drives and located the 3 connector pins that went to the HD motor. By stroke of sheer luck I happened to have exactly 3 wires with crocodile clamps left (all the other wires let out their majic smoke; in my experience they make great fuses too. Cheap trashy wires with just a few thin copper wires. I usually replace them with thicker wire after they burn out). Connected the 3 crocodile wires to the printed circuit board (PCB) with bits of paper preventing short-circuits between them, the other ends of the wires going to the motorconversion (the motor, which was converted to a generator, but is now being used as a motor again. If you can still follow me...)
Needed to find another wire to trick the ATX PC PSU into operation. Green wire to ground and it lives. And, as if by magic, the motorconversion starts to turn!
Great!
But... after about one second it stops turning and starts buzzing. I get the same effect when I manually block the HDD motor. It buzzes and won't start again. Could be an overload problem, or could be that my motorconversion doesn't spin up rapidly enough (accelerates too slowly) ? Who knows.
A 1.3 MB .avi file can be found in the link below. It shows the motor starting up, then stopping. As I turn the PC PSU off and on again it starts up again.
http://www.otherpower.com/images/scimages/3538/brushless_dc_motor_experiment.avi
I may try some other HDD boards as well, maybe they'll work better. If they do, it might be worthwhile to figure out how to modify the boards for variable RPM. If not, I guess I'll have to build a brushless motor driver from scratch.
That's all for today, dear diary. Talk to you again soon.
XXX,
Peter.
