david.evans@canremote.uucp (DAVID EVANS) (04/30/89)
I've been wonderring what ways there are to slow down the rotation speed of 3.5" floppy drives. Is there a way to do it through software, or do you have to install a POT on the motor power lines or something. I've been curious about this for a while. Any help would be appreciated. ---->Dave --- * Via ProDoor 2.9a --- MaS Relayer v1.00.00 Message gatewayed by MaS Network Software and Consulting/HST Internet: david.evans@canremote.uucp UUCP: ...!tmsoft!masnet!canremote!david.evans
cmcmanis%pepper@Sun.COM (Chuck McManis) (05/03/89)
In article <89043012060267@masnet.uucp> (DAVID EVANS) writes: > I've been wonderring what ways there are to slow down the rotation >speed of 3.5" floppy drives. Is there a way to do it through software, >or do you have to install a POT on the motor power lines or something. >I've been curious about this for a while. > Any help would be appreciated. First, you have to understand floppy drives. Several of the *old* bytes (like 1977 - 1980) had articles on how a floppy drive worked. Most drives are like the one in the Amiga, or fixed speed. Depending on the drive they fix the speed by tightly controlled motor voltage, a tachometer feedback system, or a mechanical limiter such as a governer. The tach's are the most accurate, the motor VCO's are the least expensive. Generally governers are restricted to the larger drives like 8" floppies. The second thing you have to understand, is that the design engineer had "300 RPM +/- 5%" on his specification sheet when he designed the drive, not "200 - 400 RPM +/- 5%." The difference this makes in the drive design can be quite astonishing. So you instead of trying to make your drive do something it was never designed to do (and in fact it's designer may have installed safeguards to prevent it from doing), you want to get a drive that was designed what you want to do. One such drive is the one designed to work with the Macintosh computer. So first thing you do is get a Mac "compatible" drive. Then you need to get a copy of the Mac drive interface so that you can duplicate the technique they use to control drive speed. On another note, if you want to vary the drive speed of an Amiga drive within the +/-5% it was specified at, usually an adjustment pot is provided on the bottom for that. --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you. "A most excellent barbarian ... Genghis Kahn!"
jesup@cbmvax.UUCP (Randell Jesup) (05/03/89)
In article <102409@sun.Eng.Sun.COM> cmcmanis@sun.UUCP (Chuck McManis) writes: >On another note, if you want to vary the drive speed of an Amiga drive >within the +/-5% it was specified at, usually an adjustment pot is provided >on the bottom for that. Actually, we specify drives at +-1.5%. However, we also allow +-5% clock variation at the amiga end, so unless you're running a genlock, +-5% isn't a problem. -- Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup