3.5" floppy drive question(s)

[Tony Duell]

> 
> Chuck Guzis wrote:
> > The first issue is to get the drive to ignore the difference between 
> > 1.44MB and 720KB media 
> 
> I think drives nearly always do the detection via a microswitch, don't they? 
> (It wouldn't surprise me if at least one wasn't using some kind of optical 

Those full-height Sonys that I mentioned (which don't, of course, handle 
HD media [1]) use mechanical sesnors for disk-inserted and write-protect, 
which move little plastic 'flags' into slotted optoswitches. It wouldn't 
suprise me if at least one HD sensor worked that way.

[1] The disk-inserted sensor pin lines up with the position of the 'HD
hole' so the drive thinks it has no disk if an HD one is put in. I have 
been told this was deliberate, the HD media is of a higher coercivity 
than the DD (altough much closer than the differnce between DD and HD 
5.25" diks), so using the wrong disk may well not be reliable.

> arrangement). In the event of no jumper, cutting traces or bridging switch 
> pins with solder should do the job I would have thought.

If the sensor is optical, then the same methods apply (cut a trace to 
force it 'dark', short the phototransistor to force it 'light').

-tony