[sebhc] hard sector substitute

Carroll Waddell CarrollWaddell at sc.rr.com
Sun Jul 11 19:28:24 CDT 2004

Dave Dunfield wrote:

>>Suppose you are copying files from one H17 to another H17 disk. The
>>device that is creating the fake sector holes has to wait for a pair of
>>index holes (one full revolution) each time it switches disks. So, while
>>my hardware circuit worked, it was slower than real disks because of the
>>extra time the H89 spent waiting for the disk to get "up to speed"
>>(really, for the PLL circuit to lock in and start producing valid sector
>Does the H17 switch each drive motor off when selecting drives for a disk
>to disk copy?
>The N* does not - when copying one disk to another, both drives stay on,
>and the drives simply get selected back and forth.
>In fact, there is only one motor-on signal, so all drives come on for any
>operation. Most drives can also be modified for "motor on select", however
>every drive I've seen that does this also implements a timer so that the
>drive remains on for a period of time between selects.
>I've thought about building such a device, and I decided that it would be
>best to attach it to the drive (ie: one per drive - not one per controller).
>Basically, an itty-bitty micro (PIC, AVR etc.) would have to be able to see:
>  - Motor on signal (to the motor - not necessarily the drive interface)
>  - Index hole sensor (even when drive deselected
>And be able to drive the index hole output back to the drive (so it would be
>gated by select) - alternatively - gate it externally.
>The MCU would watch the index hole, and could time how long from one edge
>to the next - after 1-2 revolutions (depending on position if index hole) it
>would be able to insert phony pulses to simulate the other 10/16 holes.
>By watching how long after motor-on before the first index pulse, you can
>handle cases where the index hole is near the sensor and the drive is not
>up to speed for the first pulse.
>As long as the motors are not turned off, you can continue to "sync" and
>no further time is wasted. If the system turns the motors off when switching
>from one drive to the other (I can't imagine a system that would do this),
>you could add the Motor control to the output of the device, and implement
>your own timer to delay shutting off the motor.
>An alternate solution:
>- Take a dead drive And modify it with a homemade punch that can punch
>  through the index hole.
>  - Put a 10 sector disk in it - carefully line up the 11th hole and put it
>    in the drive - mark this as the "master" position on the drive wheel
>    (Assuming a direct drive)
>  - Move the wheel for each of the other sectors, and mark the position on
>    the wheel
>- Now you have a jig for making 10-sector disks:
>  - Align soft-sector diskette to put index hole in position
>  - Aligh wheel to master postion and insert disk.
>  - Move wheel to other marked position and activate punch at each position.
>Tough part would be making the punch - any takers?
I've been thinking about this. What I thought about was modifying an old 
diskette drive to punch the holes automatically. It would have to be 
modified to remove part of the drive where the index sensor is located. 
A slideable pice could be built that contains both an index hole sensor 
and a hole punch. A solenoid (or whatever) could move the index sensor 
so that it could sense the hole in the diskette. If there were a stepper 
motor used to rotate the disk, a Basic Stamp could rotate the diskette 
until the hole is sensed. This would be the 0 degree position. The 
slideable punch could then be positioned over the existing hole in the 
diskette and the jacket. The stepper motor could then be rotated 18 
degrees and the first new hole punched. Next, the stepper motor could 
rotate the diskette 36 degrees (repeating this ten more times) to punch 
the remaining sector holes. A solenoid or something could be used to 
operate the hole punch. VIOLA!   A new hard sector diskette made from an 
existing soft sector diskette.

The difficult part would be to make the slideable index sensor / hole 
punch device. It would have to be thick enough and with a slot into 
which the diskette jacket could fit.

Any new thoughts?


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