If you’ve ever used an Apple II computer, then you’ll remember the click-clack-whack sounds of a 5 1/4 inch floppy drive. The internal stepper motor moves between tracks on the disk, and every step makes an audible sound. When the computer first boots, it makes an unforgettable buzzing sound as the stepper is repeatedly whacked into the mechanical stop at track 0. By comparison, running an Apple II with a Floppy Emu disk emulator is silent. Should we add back some of that old-fashioned noise?
I built a simple circuit with a 12V relay that’s controlled by the Phase 0 signal on the disk interface. Phase 0 is one of the four control signals for the disk stepper motor, and ignoring the other three signals won’t produce totally authentic sounds, but it’s pretty close. The circuit uses a transistor, so the coil current won’t be drawn directly from Phase 0. The relay here isn’t actually controlling any load – the coil is energized simply to create a mechanical click sound. And it works! Here’s the demo:
Relays can be awkward to work with, they require a comparatively large amount of current compared to digital circuits, and a diode to prevent dangerous voltage spikes when the coil shuts off. What about using a speaker element instead? I modified my circuit to replace the relay with a tiny speaker that I had in a drawer, and change the driving voltage from 12V to 5V. To be honest I have no idea what the speaker’s specs are or how much current this might be drawing from the supply, but it works:
I was considering integrating a click relay or speaker into the much-discussed Floppy Emu daisy chain adapter. What do you think? After running these tests, I’m less excited about the idea than I was initially. It’s fun for a few minutes, but after that I’m concerned it would grow irritating. I could include a disable switch, but it seems foolish to incur the expense and design time of adding this extra feature if most people will turn it off anyway. Relays and speakers aren’t exactly cheap either, at around $1.00 to $1.50 in the quantities I’m looking at, making them more expensive than a microcontroller. Rapid on-off switching of the coil or speaker current will also generate electrical noise in the power supply and disk I/O signals, increasing the chances of disk errors if the signal quality is already marginal. So even if cost isn’t an issue, malfunctions are still a risk.
Of the two versions, I think I prefer the relay’s more authentic sound, but the speaker would be easier to work with and probably less likely to cause electrical trouble. Either one could work. Aside from the difference in tone, the speaker also produces a different series of clicks than the relay. The speaker can respond more quickly to changes on Phase 0, while the relay’s mechanical design likely misses any Phase 0 pulse that’s shorter than a few milliseconds.
If most people feel this is a compelling extra feature, and they wouldn’t mind the few extra dollars in cost, that’s great. But if the reaction is more mixed or merely “would be nice”, then I’ll probably leave it out.