Floppy disk portable music player

Well, so far I have figured out that floppy drive can be wired up in such a way that it will move the head one track step per revolution of the disc, and that the head direction can easily be controlled. Still having problems getting the spindle motor slower - my floppy drive is a more recent one, as such the motor controller chip is apparently a custom / cheap non-descript item that I have been unable to find any data sheets for...
I have a couple of others somewhere, I'll check them out when I find them.

Anyhow, provided the motor can be made slower (or better yet, used in constant linear velocity mode rather than the standard constant angular velocity) this will allow the disk to store much more audio (don't know how much yet), but if stereo audio is dropped and instead a mono track is used, then BOTH sides of the disk are available as a 'continuous' track by simultaneously switching the head direction and swaping to the second head / "B" side (on the other side of the disk), at the exact moment the head reaches the end of the last track on the "A" side. This is easier than it sounds - the drive produces an index pulse once per revolution of the disc (used to time the track change of the head, by the drive controller). This can be used to monitor the head position (track number), the start / end of each track, and as the trigger to start reading the "B" side of the disc, by counting the index pulses.

Basically it will at least double the ammount of recording space available. A small micro controller might be needed to control the drive, but other means may be possible. A simple and cheap PIC chip should have more than enough power to do this task.

Still trying to work out a way to get stereo audio on a single track (I have an idea based on a MUX, but I need to test to see if it's possible).


I can post up the info for what pins control what, on the drive's cable connector, if you wish to experiment yourself.

SS

Siliconous Skumins wrote:...Still having problems getting the spindle motor slower - my floppy drive is a more recent one, as such the motor controller chip is apparently a custom / cheap non-descript item that I have been unable to find any data sheets for...
I have a couple of others somewhere, I'll check them out when I find them.

Anyhow, provided the motor can be made slower (or better yet, used in constant linear velocity mode rather than the standard constant angular velocity)...

I was under the (perhaps mistaken) impression that most floppy drive spindle motors were just stepper motors. That being the case, I also have a dim recollection of a commonly-available driver IC which took an external clock signal to control step frequency. (The L297/L298 combo used in the RepRap might do the trick.)

von Corax wrote:I was under the (perhaps mistaken) impression that most floppy drive spindle motors were just stepper motors. That being the case, I also have a dim recollection of a commonly-available driver IC which took an external clock signal to control step frequency. (The L297/L298 combo used in the RepRap might do the trick.)

Nah, the spindle motor is just a very accurate brushless 'pancake' type motor, the driver chip gets a signal pulse from the motor, which is used to adjust the RPM. The head uses a stepper motor though, an 18 degree / 20 step per revolution motor in 3.5" drives.

Usually you can just reduce the voltage on a brushless motor like those in computer fans to slow it down, but the floppy driver chip stops working if there isn't enough voltage or current.
I just need to find out which pin(s) are used for the clock signal from the motor (I know there is a hall effect sensor in there for the Index signal, but I'm unsure if the same sensor is used for the RPM clock signal), and by altering the clock signal, it should adjust the speed of the motor. Depending on how the motor RPM sensor is setup, it may just be a simple case of adding a second sensor at 180 degress out from the original sensor, thus doubling the clock pulse / slowing the motor to half speed.

I could just use another driver for the motor, but the existing chip would be better due to the fact it keeps such accurate speed on the motor - something thats important for analogue audio - and the fact it keeps the costs down.

SS

Thankyou for doing all this SS, I'd never have known what to do with half of the things you've mentioned here!
I can't express my gratitude enough

JingleJoe wrote:Thankyou for doing all this SS, I'd never have known what to do with half of the things you've mentioned here!
I can't express my gratitude enough

No probs, I'm actually quite enjoying the challange! And you knever know, it might be worthy of a mention on Hackaday (if it works...)

SS