11 Jun
2013
11 Jun
'13
12:41 p.m.
On 06/11/2013 10:51 AM, David Riley wrote:
On Jun 11, 2013, at 10:27 AM, Philipp Hachtmann
<hachti at hachti.de> wrote:
This is something that can be done retro IE: DPLL using standard TTL
(counters and a 555 timer).
Thee goal is to produce 16 pulses for 1 rotation using index or the
existing 12 pulses as "reference".
The trick to it all is not making a complex hash of it. If you know the
rotational speed and
you have an index pulse then you have everything needed to phase lock an
oscillator to the rotation
of the shaft (motor speed) and if the oscillator runs at 16x that rate
you have your sector pulses.
What makes this eassy is if memory serves the motor is synchronous type
so its locked to
the 50/60hz line frequency making its speed very constant and speed
changes are over time
less than typically .02%.
This is a rehash of the same problem for NorthStar* hard sector disks to
use soft sector media.
The difference there is 1o sectors and the floppy only provides index to
sync on. That and floppy
motors are not as speed controlled (sa400 and TM100 types).
In both cases you have an index once per revolution and sector pulses
that may not be coincident.
Usually the timing is fixed relative to each other.
Allison
Hi Ethan,
On 11.06.2013 07:59, Ethan Dicks wrote:
I'd
assume you're thinking along the lines of a simple digital PLL
using the capture/compare functions of the timers? That could be
done with a VERY small AVR/other micro indeed.
If you wanted to make it more "retro", you might be able to do it
fairly simply with a 6502 and 6522. :-) Still more modern than
the RK05's internals, though, and I have no idea how much space
is available in the box there.
- Dave
I'm an instructor at our local makerspace
(the Columbus Idea Foundry) - I teach
electronics (incl. Arduino and Raspberry Pi workshops and run the monthly
3D printing meetups). I would *love* to have some instructions to follow to
make either hubs or electronic 12-sector-to-16-sector pulse regenerators, but
*designing* such things is a bit beyond what I can do on my own.
If I get it to
work, I'll build some and sell them. The hardware design is quite primitive: An AVR,
crystal and some passive stuff. The trick will be the firmware.
I'm quite sure you would be able to design the pulse regenerator!