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HDDJ: Turning an old hard disk drive into a rotary input device

Step 7Video summary

Here we have a video summary, showing the HDD connected to:

1. A comparator circuit, which amplifies to the output from the motors.

2. An oscilloscope, which shows the nice amplified square waves.

3. A microcontroller, which takes the square waves as input and uses them to determine the direction of spin. The microcontroller outputs (via serial line) the "<" character while the disk is spinning counter-clockwise, and the ">" character when it is spinning clockwise.

4. A computer, that takes the output of the serial line and shows it on the screen.

In the video we're pretty excited because we just got this working for the first time :)


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9 comments
Feb 4, 2012. 12:11 AMcharlyv says:
Wow, what a way to steer a boat.
Like flipping the disk, each few revolutions being a degree of turn and then when you stop the disk, the processor nulls the rudder. Would make it so easy to navigate with a GPS in a narrow area. Some ideas on how to implement hydraulic or heavy servo mechanics using the control output of your design.... gonna look that kind of scenario up...
Thanks!
May 1, 2011. 6:55 AMMECHOL says:
incomprehensible
Dec 25, 2010. 8:47 AMefiscp says:
I'm gonna implement this as a scrollwheel. A very fast scrollwheel. ;)
Feb 20, 2010. 7:07 PMkennethchaco says:
 can i conect that to arduino duemilanove?
please help
Sep 10, 2009. 7:13 PMmaxout says:
nice project can't be done without details on part list yet i still want to build it.. i am itching to scratch lolz.. also is this connected thru USB? i mean what software u test it with? Virtual Dj, etc? please if you can do this project in detail on WIKI would be great.
Apr 14, 2009. 11:44 PMkyle.marsh says:
Coffee bean: would that be the opposite of defragging?
Sep 2, 2009. 11:54 AMReCreate says:
Just remove the de, Fragmenting...
Nov 15, 2008. 1:32 PMBrett_cgb says:
Nice project – I think I’ll replicate it (the portion that uses the disk motor as a flywheel controller). I suspect that the common Neg reference for the LM324 should be connected to one of the other pins on J2 (whichever one you used for the 3-phase scope captures), and that it should be biased to 0.25Vdd (one quarter Vdd – see the LM324 requirements for input signals). This raises the reference and all the motor phases to within the supply rails of the LM324. Ideally, you would see a 3-phase digital representation of the 3-phase motor signals. Firmware needs to see any two phases to determine speed and direction. When one phase rises, this triggers a step. Check the state of the other phase to determine direction.
Nov 14, 2008. 11:26 PMt.rohner says:
Good idea and a very nice oscilloscope you have...
Nov 13, 2008. 4:22 PMCoffee bean says:
DUDE u have it put it to music and then u can say u remixed your hard drive.

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