I offered to write a technical document on floppy drive theory of operation for preservation purposes. As part of my documentation, I wish to include circuit models for the R/W head as it is passed through various amplifiers and filters. I chose to discuss the Shugart SA800 because there exists copious documentation for the drive.
I have the schematic diagram for the drive including from this link, page 39: http://deramp.com/downloads/floppy_drives/shugart/SA-80x Maintenance Manual.pdf
And a circuit model for the R/W head is provided here, page 21, figure 28: http://www.mirrorservice.org/sites/...64-0_SA800_801_Theory_of_Operations_Apr76.pdf
Neither of these are quite in depth as I was trying to get. The diagrams in Section 4 of Theory of Operations, provide a nice model for how flux transitions are written and read for a ring magnet and a single coil. However, a real Shugart drive uses two coils, and during a read only one of each coil is active for a given direction of magnetism on the disk surface.
I'm having trouble understanding how the provided R/W circuit model works; I'm not certain how the floppy disk is capable of only inducing a current through one of the coils at a time when the whole head would be exposed to the change in magentic flux. The diodes which connect directly to the head coils from the read amplifier (page 39) are also limiting my understanding b/c an induced voltage will reverse-bias the diodes and STOP current flow. I suspect the knowing way that the R/W head coils are wired would make understanding. I also suspect that I've forgotten how to use Faraday's Law properly XD.
Is anyone familiar with floppy drive physics or is familiar with how R/W heads were typically manufactured? It seems that fully understanding this circuit is dependent on knowing how both coils are oriented. I SUSPECT they are in the same position and just wound in two different directions. Or maybe my analog electronics needs work.
I have the schematic diagram for the drive including from this link, page 39: http://deramp.com/downloads/floppy_drives/shugart/SA-80x Maintenance Manual.pdf
And a circuit model for the R/W head is provided here, page 21, figure 28: http://www.mirrorservice.org/sites/...64-0_SA800_801_Theory_of_Operations_Apr76.pdf
Neither of these are quite in depth as I was trying to get. The diagrams in Section 4 of Theory of Operations, provide a nice model for how flux transitions are written and read for a ring magnet and a single coil. However, a real Shugart drive uses two coils, and during a read only one of each coil is active for a given direction of magnetism on the disk surface.
I'm having trouble understanding how the provided R/W circuit model works; I'm not certain how the floppy disk is capable of only inducing a current through one of the coils at a time when the whole head would be exposed to the change in magentic flux. The diodes which connect directly to the head coils from the read amplifier (page 39) are also limiting my understanding b/c an induced voltage will reverse-bias the diodes and STOP current flow. I suspect the knowing way that the R/W head coils are wired would make understanding. I also suspect that I've forgotten how to use Faraday's Law properly XD.
Is anyone familiar with floppy drive physics or is familiar with how R/W heads were typically manufactured? It seems that fully understanding this circuit is dependent on knowing how both coils are oriented. I SUSPECT they are in the same position and just wound in two different directions. Or maybe my analog electronics needs work.