Open Music Labs Forums

Hi OML users!

I just finished wiring this madly wicked project up, and I am so grateful to finally having it spit audio out of my speakers!

To sum the process up:
I wired the red (5v+) and black GND power cables up to my arduino uno and grounded pins 14 and 10.
(used the arduino for pin 18 and 20 - direction and stepping pulse)
I managed to solder some wires onto the W/R heads (checked for the GND line with my multimeter - one didn't have any resistance so I figured that'd be the one).

The input was gained through a behringer mixer and the output was hooked up to the tape heads of and old Fisher Price tape recorder. :)

I then tried to accomplish the following: adding my own pulse to the spindle motor as this guy did:
http://www.instructables.com/id/floppy- ... d-control/

I then ended up with somehow screwing up the motor and now it is jammed and just sends out clicks when trying to rotate. I doesn't matter that much as I already have another drive ready for hacking.
This time I will build it into a casing and have switches for the different controls as direction and record/play, LED's for indicating write protect, track 0 and disk presence.

But I would like to find out how to adjust the spindle motor speed before throwing myself into the hellfire of soldering and wiring once more.

I tried soldering a wire to one of the pins going to the spindle motor circuit board, on the pin that got the motor running when grounded. But it wasn't the right one. The Floppy Drawbot Dude said he measured a 1 MHZ pulse on pin 5, which he cut the connection to and added his own pulse. Sounds über-neat and that's definately where I'm going!
Imagine being able to slow down the RPM of the motor and playing your audio in different pitch. The guide on instructables said it was possible to slow it down to 120 rpm before it was loosing motion, that's over half the speed of the playback! I wonder how fast it can run and still play the audio! I am so excited to do this! Hope somebody is willing to take this challenge up and test it out! (I've heard that a 5.25" drive typically has a built-in speed control knob!)

Oh, and here's some footage of the drive when it was just done - and still alive. (Notice the mess in my hut!)

YOUTUBE LINK HERE


Update:

I now managed to adjust the motor speed by following the guide i provided at page 1 (bottom), I simply cut the SPD wire, and scaled the drive voltage with a pot. It adjusts the speed to what I think is nearly 50% but there's a steep drop all of a sudden from high to low speed. Any suggestions what I might be able to do? I tried several potentiometers, all from 1K to 1M. Same.

I talked a little bit to Matthew Wenn who got it working (from the Instructables site)
and he said the following:

does the platter spin up when you ask it to over the interface? If not then you need to either pin down one of the disk detect microswitches, or fake it by forcing the correct i/o line high or low.

When you can get the disk to spin up reliably, then look for the control signal. If you don't have a scope, what I'd try is taking a 2k resistor and connecting each of the lines via the resistor to ground. When you find a line that stops the platter moving, you have a candidate.

Check the rest to be sure, because one of the lines will probably be a signal to start/stop the motor.

Another way to find the line is by looking up the driver chip and then tracing the tracks.

Hope that helps, and let us know how you get on!

Matt

My question was:

I tried measuring the wires on the 'spindle motor pcb' going to the larger pcb and I wasn't sure which configuration I had to adjust my voltmeter to. I didn't find any signal amongst the pins, but one of them sent the spindle motor spinning when grounded (pin 4 from the left) but I wasn't able to do anything useful. I think I was close but... no cigar.

Glad to post it, I am getting a kick out of the idea of changing the front page a bit more often, and it's great to have enthusiastic people posting new work.
I love the idea of a mechanical counter for spindle rotations, that sounds very satisfying, although expensive! :) I would be psyched to support your work on a product and provide a place with oml to help you to get it out there, I've been learning a lot about product design from my work with Keith McMillen lately, and I feel like the ultimate end goal of it all is to be able to help others learn similar things, so that we can all contribute our ideas and excitement to the greater good. Plus I've been stalled in my work with floppies as I have been sidetracked with other things, so if you are psyched to make a stab at it, it will get me psyched again to start getting things together.

Regarding speed, I wonder about whether or not you are right, if maybe there could be a place in 3.5 inch drives to put a pot, just like in the 5.25 inch drives. It is definitely worth investigating. If you can post the info on the drives you are looking at, I'll look through my drives and see if I have something similar, it would be interesting to be looking at the same hardware with someone. They all seem so different. When I was at maker faire with this project, I met this guy who seemed to have first hand knowledge of so much of this drive lore, and then Jeri Ellsworth walked by and said hi (which was very exciting), and someone else was there trying to talk to me, and I quickly wrote down the man's info on a piece of paper and haven't been able to find it. A bit of bad luck there, he was fascinating and deeply knowledgeable. Jeri's main comment was that so many people have asked her to put out a board that there was definite interest and that I should get a board out for people. And then all this time has passed and I haven't yet done so. Well, I didn't know the first thing about designing a pcb at the time, but now that I do (how fast time flies and knowledge multiplies!) it all seems like it would be so simple if I could just put in the time. So if you're interested, maybe we could start drawing up and sharing schematics of workable circuits and then pick and choose from them and lay out a board. I've got a few things already drawn up and just need a bit of a push to get them to be usable in first rev form.

So anyway, if you've got enthusiasm, I've got knowledge! If you're still in the midst of it all, we can compile our knowledge together and get something permanent made before you finish and move on to other projects! :) Outside of the forum you can mail me at mcanulty [at] openmusiclabs.com. But posting as much as possible on the forums is very valuable, people do find the post and learn from them.

And for the ultrasonic sound to erase the disk, I wanted to build some simple circuit, based on 555/556 timers and came across this schematic on a dog-repellent project.

The ultrasonic dog repellant uses a standard 555 timer IC1 set up as an oscillator using a single RC network to give a 40 kHz square wave with equal mark/space ratio. This frequency is above the hearing threshold for humans...

Link here:
http://electroschematics.com/1026/dog-r ... t-circuit/

Those two resistors after the buffer stage are a scaling stage, I can't remember why I wrote down that I was putting it through another scaling stage immediately afterwards, it might be because I was actually amplifying the bias when I was erasing, and then just adding it when I was writing audio, so I split them into two stages.

Woah, good find!

I'm drawing a complete diagram of how I want to build this bastard, I got to the stage of the signal bias and read your post and illustration - thanks a lot BTW! - I'm not sure I really get the drawing you've made but I think the main issue would be summing the signals without some weird impedance-loss and all this bizzare stuff that I'm not that educated on yet, but I think my conclusions for my build is:

RLC oscillator for the bias! (easy to build and pretty neat for producing a fixed sine wave signal)
OMP-AMP for summing the signals (as it's inverting the phase, afaik)

wadd'ya say?


EDIT:

Okay, seems like it'll be no problem as I'm already planning on driving my input to the FDD heads through a OP-AMP circuit, and as far as I can tell, it just requires a few resistors between the bias signal and the OP-AMP input!

Oh yeah, I could imagine the motor running yerky with a low frequency in the pulses. Still interested to do it though!

I figured out how to fix the sudden speed change to a nice and smooth speed change. I sent out a PWM pulse from my dear arduino and changed it into a analog out with an RC-circuit. Video will be up soon!

guest wrote:what value R and C did you use?
what is the PWM frequency? a higher PWM frequency may not require the filter.

Acutally a filter may not be required at all but then there will be no need for PWM either. The SPD pin on the spindle PCB takes float voltage, the CLK can be sent a ~1MHZ signal to drive the spindle motor.
The thing is, I tried with just taking a pot and scaling a current between 0 and 5V, directly to the SPD pin and there was this (as before mentioned) very steep transition between the highest and lowest speed on the middle position of the pot. I tried converting the PWM signal to "analog out" with the RC filter and now it works smoothly.

(I used the values 4,7K res. and a capacitor of 1uF.)

Oh yeah and the pulse freq is determined by a potentiometer to Analog In on the AVR. Just scaling between 0 and 1023.