Update: This page is just an archive. The real work is continued as a walk through. Please direct all your comments to that page.I am the proud owner of a stack of scavenged hard drives. I hoped to find really fast, torqueless motors inside. But instead I found myself a project for my new found 555
question…
Should this be a walk through or tip?
8ik
Most definetly! Chage title
Most definetly! Chage title to "how to…" and go!
Looking forward to dive more into this 
And thanks for making it.
If you re-enter, PM me or something, or BOA or Dan, to delete the blog entry. If you want to keep a record in your blog, you can aso re-enter this as a tip, and just change the blog entry to a "today I made this: (Link)
Cool, always wanted to use these motors…
Very interesting video. I
Very interesting video. I never knew that the spindle motor on a hard drive is an induction motor. I guess that makes sense – they want it to be as quiet and long-lasting as possible, so it seems like the obvious choice.
I’ve been looking at lots of electric cars and power tools that use brushless induction motors, and I knew that they were driven by alternating current (single phase or three phase) rather than DC. I know that on the big motors, they usually use an inverter to generate the alternating pulses from a DC power source, which seemed like too much complexity for something smaller like a robot. It’s interesting to know that you can generate the pulse train from much simpler hardware.
I guess since your three outputs go from 0v to full voltage, what you’re generating is three square waves, whereas regular AC would be a sine wave. So I imagine the motor might not run quite as smooth with your driving method? Maybe the difference isn’t really noticeable.I wonder how the HD’s onboard controller drives the motor – with an on/off approach like yours, or by generating something closer to a smooth sine wave? Anyway, thanks for the info.
Dan
Would a simple component not
Would a simple component not even out the square, make it more sine, I wonder?
(We HAVE to get some of them oscillo-thingeys!)
Best part of the video not shown…
I have GOT to see the tripod-camera-mount-desk-lamp-camera-holder-thingie!!! Brilliant!!
No, seriously… I love things done without a "brain" just simple logic chips… Good stuff!
fitting a square wave into a round motor
You’re talking Capacitors. I believe those are also used to “round off” the sharp corners on a CDROM audio signal. It’s the size that I cannot fine tune in my current setup. I need a scope for that indeed.
Also, I was hoping the inductance of the motor might help out. The fact that current through the motor drops with higher RPM seems at least hopefull.
8ik
I figured you would.
Do you recognise its intended purpose>
Brushless DC drivers
Here’s a pic of a typical brushless DC motor driver circuit.
Each "half-H" is usually driven in a sequence according to what is read from the hall effect sensors. Each phase would begin with the upper transistor on sourcing the connection, then both off not conducting, then the lower transistor on sinking current. THe second phase follows with the upper high at the time the first phase goes neutral. So each corner alternately goes from sourcing another to sinking from another. Some controllers can be "sensorless" and simply commutate and hope the motor is following. Some model airplane controllers are like this. But they work.
Wikipedia has a few general details. Pretty cool that you've got it moving pretty well. Thinking of making a POV device? or a laser scanner?
the same but different
The motor you are showing has a "delta" configuration plus hall effect sensors.
The hard drive spindle motors I collected do not. The are in "Y" confiuration and have no sensors. It is thinkable to use the induction in a non-powered coil as sensor though.
I like the idea of reversing the current through the coil. Of course timing that would be even more crucial.
8ik
Wiki wiki wiki
THe Wikipedia link above shows both delta and Y configs, and both are driven similarly. And hall effects do not have to be there, they simply can help. Back EMF sensing can be used too, I think that may be a different way ot refer to induction sensing.
that’s what I meant
back emf sensing indeed
trust me: i’ve found the wiki way
and i am determined to put this piece of thery into practise for all of us to learn from
8ik
This Thread Has Moved
Update: This page is just an archive. The real work is continued as a walk through. Please direct all your comments to that page.
Hi, I’m new to electronics
"This thread has moved"
Update: This page is just an archive. The real work is continued as a walk through. Please direct all your comments to that page.
I was trying
I was trying this out… but for some reason… the sequence stops after a random time interval… its not a fixed interval…
