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Old 23 March 2014, 10:41   #259
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Join Date: Mar 2012
Location: Norfolk, UK
Posts: 564
Originally Posted by mamejay View Post
If you tell me the values of the resisters, capacitor and also what transistors you used I can draw up schematics of this.
Well I've drawn up a rough schematic, since it's the easiest way of explaining what I've actually done - but there may be a better way of doing it, and the resistor values could probably do with adjusting.

What did you use to get the sound?
I'm using the "step" pulse from the floppy interface to make the sound, and the rest is simply to trigger the piezo sounder. (Note that the Gotek pulls the Step pin up to 3v3, not the usual 5v.)

I sometimes get some unwanted oscillation which makes the sounder squeal, but it goes away when I touch the sounder, so I guess C1 probably needs to be bigger?

The circuit was developed largely by trial and error, and there may be a better way of doing it. The main transistor (T2) needs to be a very fast switching type, since the Step pulse is active low and very short. It also loads down the step signal somewhat, so may need a resistor between the emitter and ground?

I'm not sure the 2N2222's even necessary, though its comparatively large storage time should be widening the step pulse somewhat.
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