Walzing Hard Drive Motors
2008-11-09 21:18
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 knowledge.
The logic chip 74164 is a "Serial In Parallel Out bit shift register" (datasheet). S1 acts as a reset button. S2 is the little white wire in the video that "boots" the sequence. Once one serial pulse makes it into the 74164, the system will maintain the sequence. When the pulse reaches the third output (red), diode D1 feeds it back to the first (green).
The motor driver is the well known L293D.
The video lasts as long as 10 minutes. Oh, and you'd better take your sea sickness medicine!
8ik
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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!)
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
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!
I figured you would.
Do you recognise its intended purpose>
Wish I hadn't thrown out those old HDD's
Very interesting, if your interested here is another 3phase generator using a 4018 that doesn't need a reset or initialise button, just a clock input.
Admittedly this isn't my design, it's from the "CMOS cookbook" and I think the output is slightly different.
I wonder how this might affect the efficency of the motor.
I was also thinking about the fact that you're using L293D as the driver. When both sides of a winding are high or low you are effectively using electronic braking. If you use open colector outputs then the windings will either be on or off with no braking. Since this is a three phase motor and direction is changed by swapping any two of the phases you could replace the L293D with three NPN transistors.
I will dive into these
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
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
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