Friday, 30 September 2011

What can you salvage from a floppy disk drive?

In true Nerd Club fashion, no sooner have we decided to start (or re-start) a project, and something else comes along and takes our attention away. This time, it was the postie bringing us a clutch of four floppy disk drives, won off eBay just 48 hours earlier.

Why would anyone want such old crappy hardware?
Well, for a start the winning bid was just 1p, so even allowing £3 for delivery, they came to less than a pound each. (if you're ever at a car boot, and someone is selling off job-lots of drives as they often do, for 50p or so, it's worth grabbing a few). But that's not the main reason - we actually went out looking for old floppies, as a source of cheap stepper motors.

Here's what we found in one of our floppy drives:

The bit we're interested in is the stepper motor - usually seen at the back, next to the IDE cable connector. Whip the lid off and take a look. The motor usually has a corkscrew shaft and a bit of grease on it. These aren't important right now.

Normally two screws is all it takes to get the motor out of the casing. The other end of the shaft is usually in a part moulded into the actual casing. If the shaft and casing are all one unit (as often found in low voltage or portable/laptop drives) you'll need to undo a few more screws. But 99% of drives are built like this one.

Undo the two screws and pull the stepper motor backwards. Eventually it will stop. That's the flexible ribbon cable holding it in place. Pull until it comes free.

If your motor still has the ribbon cable attached, you can use this to connect to a PCB in future. But most messing about with steppers is first done on a breadboard/prototyping board, in which case simply solder some wires onto each of the four connection points.

The rest of the drive can be junked. We've got what we came for. But if you're in a scavenging mood, there's plenty more to be had from these little things. Get rid of the disk caddy and moving parts...

Remove the plate above the spinning head and pull. The actual spinning head should come off in your hands. It's a doughnut-shaped magnet with a spindle in the middle. It should just lift off. Undo a few screws from the bit it's sitting on and you should see some cool coils.

It's these coils that control how the head spins. As each coil is activated in a particular sequence, it can attract or repel the magnets inside the spinny head thing. If you really wanted to, you could use this as another crude stepper motor. But it's probably more hassle than it's worth. The coils themselves, however, might be useful in other projects.

Let's take a quick look at what we've scavenged from our floppy disk drive:

In our drive (though not all) we found some useful 0.1" pitch flexible ribbon cables. These are useful for joining two or more PCBs together, especially if soldering isn't your strong point - they're quite easy to work with.

There were a few springs, used to pull the disk drawer in and out, and a few "peg-style" clip springs too.

The rod that the disk head was on could always come in useful for something robot-y.
Of course, the stepper motor is going to come in handy - that's what we came for in the first place! And there were also a few "self-tapping" screws which might be handy in future. They have a slightly wider thread than normal screws and are perfect for fixing into plastic or acrylic (where they make their own thread as they are screwed into place, hence the name)

Not a bad haul for a few minutes work.
Get yourself some component bins, a few cheap drives and get to work!