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Author Topic: Making a hard disk clickity-clack  (Read 9100 times)
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Rodrigo Constanzo is a performer and composer living in Manchester, England. He is an avid improviser and performs regularly using home made electro acoustic, and modified electronic instruments. He is currently working towards a PhD in Composition at th
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So I'm working on the development of an instrument that will, when it's done, be about 4 computer hard drives, 'open face' where they would acoustically be clacking/reading away.

Would it be possible to control a hard drive that way with an Arduino? As in the arduino itself driving the harddrive (not power wise, but control wise).

The idea I have is that, on being triggered, each hard drive would start reading/clicking and then die out (doing less and less). This could be triggered over and over.

I plan on building all of them onto a resonant (wood) enclosure to help amplify them a bit, but I definitely want to keep the computer out of it and do everything in the Arduino (if possible).

I also don't know what type/era of hard drive would be best for this type of work.
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Can't tell you much about HDs, but maybe this one's interesting as well.

http://www.codeproject.com/KB/system/floppystepper.aspx
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The idea I have is that, on being triggered, each hard drive would start reading/clicking and then die out (doing less and less). This could be triggered over and over.

You can control the VCMs easily enough with a motor driver chip or even just some transistors and PWMing it.

They're what make the head move and make it 'click'.
Controlling the motor itself would be more tricky but most hard drives will spin up the motor even if nothing else is connected apart from power so you could control the power to the HDD with a transistor and just turn it on when you want the motor to spin.
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Not interested in spinning the platter at all, actually thinking of using them as rotary encoders to control other things.

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Ok - just throught I'd mention it.

The VCMs are easy enough to control - just play around with a transistor and a voltage smiley
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Is VCM the name of 'the arm thingy' ?

Would it just be a matter of sending it voltages so it goes full one way, then full the other way, to make the clicking sound? That seems fairly easy. I was assuming it would need actual read/write information to get it moving.
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It's called a VCM (voice coil module - don't ask me why) and yeah it's the name of the 'arm thingy'.
They reside to one end due to the magnetic field on them, then you send a voltage to get it to move to the other endstop. You can then remove the power and it will click back to the initial position endstop.

It's pretty simple.

People have used them for laser projectors (I'm kinda in the process of doing this) - by PWMing them you can get them to go to a specific position rather than just flick backwards and forwards.
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That's perfect. I could probably throw in some PWMing too so it's not always the same 'click' sound, but varies depending on how far back it has to travel.

Have you got a schematic of the hardware side of what you're working on?
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I don't think you connected the grounds, Dave.
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I also don't know what type/era of hard drive would be best for this type of work
Not a recent SSD one, for sure!

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It's called a VCM (voice coil module - don't ask me why)
Because it is the same mechanism used in a loudspeaker - a coil in a permanent magnetic field.
Modern ones have a circular action, but early ones were linear.
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Have you got a schematic of the hardware side of what you're working on?
Nope - just stick an arduino output to a transistor gate (2N3904 or something should work) through a 1K or so resistor and connect the VCM to +V (something as low as 1.5V works but I'd go with 5V or higher) and the other side of the VCM to the transistor collector, transistor emitter to ground.

Mowcius
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Sweet, I'll give that a go.

Now I just have to find a sufficiently old/loud harddrive to make this worthwhile (modern ones are so quiet).
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Now I just have to find a sufficiently old/loud harddrive to make this worthwhile (modern ones are so quiet).
They're not so quiet when you have the case off and when you are making the VMC hit the end stops. Hard drives don't normally click because the VCM is controlled so it doesn't hit the end stops. Something like an old 40GB Maxtor works fine (and you can get them from anywhere - they were used an awful lot around the millenium - and many servers/desktops died an early death because of them smiley-razz )

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Just hook onto the voice coil as if it were a speaker and pipe some analog signal at it. Heck, pipe some music at it. Literally any magnetic-platter hard drive will work - from the first one to the ones they'll be building Next Tuesday. You just might be surprised at the result - they're actually quite good speakers.

If you're looking to use them as a percussion insturment, just throw them all the way to the bump-stops for a satisfying CLACK.

The easiest way to get access to the voice coil is to pop off the PCB on the bottom (discard it, harvest it for parts, whatever) - that PCB will mate to either a ribbon cable or terminals at two spots: the hub of the main spindle, and a second set with 4+ pads near the hinge for the arm. Poke around on those 4 pads (I recommend using bare speaker wire connected up to a nice, loud radio) and eventually you'll find it the right two connections. You don't need to apply any power at all to the hard drive unless you want to pin up the platters - a lot of drives make some pretty cool sounds on spin-up, so you may want to look into that, too. The spindle motors usually respond well to 12vDC.
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An update on this stuff.

I did a bunch of testing at a friends house who has oodles of old HDs. After testing over 10+ drives I found that Seagate "Medalist" drives were the best (clocking in at 2gb on two platters).

The way they are built makes it easy to access the voice coil. The click is satisfying/clear, and once you remove the little rubber bumper that helps preventing the clack, it's even louder.

I have two identical drives now, and each has it's own unique sound, which is interesting.

Here is a pic of the testing:



(the seagate is the bottom/left most drive)

Now as to driving them. We started by just sticking the speaker out of a home hi-fi setup and it worked right off the bat (once we found the points to connect to). Music sounds like music but very quiet/tiny sounding (like a DIY turntable with just a needle going into a cup).
We setup a puredata patch to spit out low frequency squarewaves that changed pitch and rate of change randomly.
This worked the best as it threw the needle around pretty nicely.

At the right volume level (as in, hi-fi volume crankedness) you get the most awesome clickity-clack going.
The problem (at the moment) is that it has to be very loud. Like plugging the speaker back in is "we're have a house party and our neighbors asked us to turn it down" kind of loud. His hi-fi is rated at 40w (or was it 60?), point is, pretty high, and out of reasonable battery powered volume.

I tested it just now, for fun, with my 386-based pocket amp and it made not even a blip.

I really want to build this into a self-standing wooden enclosure, so I want to avoid having a massive power amp in there, then of course is the problem of producing the actual audio. Since squarewaves aren't too weird I figure an Arduino can spit that out and it's low power consumption.
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I don't think you connected the grounds, Dave.
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I smell spam.
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"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

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