oscillations in isolation

[duck_arse]

you know how it goes. we've* all done it - bought 300 or so 4N25's cause you thort they was something else, something useful. and then found out they weren't, wouldn't do anything interesting. well, here's one way to get rid of some - build a cross-coupled oscillator with optical modulation of mark and space! also, kV isolation rating!

click the colour image if you must have a black and white instead.


I've had this on the breadboard, it runs a treat. by treat, I mean the mark/space is not 50% across the rate pot range, but that's no matter. you probably want something to drive those two modulation leds, like another osc or an envelope, something. even a pot to supply, 100k would do. you can set one with a pot and modulate the other if you want, I'm not your boss.

output is a squarewave, basically, with R//C leading edge. you can drive a led as shown, or a led to ground, from either collector, or take audio - or sub-audio - from either collector via a cap. the C51 cap can be switch-paralleled with a larger for to correct shifting duty cycle, but you prolly knew that already. no values are critical, other opto-iso's can be used as long as they have the external base connection.

uses? I dunno. jabber? enough! enjoy.

ahh, one final point - I didn't have the indicator led attached while messing with this instance, but have proved that connection on a different design.


* no, not me, either.

[duck_arse]

I should perhaps point out a few things I should have pointed out. if you are using this for audio, you wouldn't have the LED1 or R59 fitted. as for uses, I think it would be best used in something like a many oscillator noise maker (because of the way the tone will change with freq). like the one I'm working on at the moment. I had planned on this as the hunka chunka colour adder, but didn't spend enough time getting it working like I thort it should.

[moid]

I know this is of no use whatsoever but your post title makes me think it should've been a Silver Apples song

[Phend]

Didgeridoo clone.

[MaxPower]

I thought it sounded like a title to an early Tangerine Dream album.

[duck_arse]

interesting on both counts. messing with the 'other' panel, I was sometimes hearing Suicide bass lines, Frankie, and at other times it was throat singing and or didgeridooing.

[Kipper4]

Guilty *

Nice one mate.
Been busy gardening, haven't had chance to listen to the files yet.
Sorry very distracted right now.
Rich

[Rob Strand]

Didgeridoo clone.

The very first issue of Practical Electronics magazine (Nov 1964) had some sort of didgeridoo circuit.   I saw it when randomly poking around the Practical Electronics magazines after the First Pedal thread.

[duck_arse]

yes, kipper, youse are.

you ready for the full panel schems yet?

[Kipper4]

Not yet mate. Totally not in the right headspace yet.
Sorry. Having a hard time.