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 Forum index » DIY Hardware and Software » Thomas Henry designs
Basic LFO
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 170
Location: N. Mankato, MN
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PostPosted: Sat Jan 17, 2015 10:52 pm    Post subject: Basic LFO Reply with quote  Mark this post and the followings unread

Hi Everyone,

Just for the hell of it, I decided to return to the basic Schmitt trigger-integrator, just to see how much I could wring out of it without the usual stupid range-switching. I maxed out at a 286:1 sweep range, which isn't bad at all for such a simple design. This really is a reliable old warhorse. I've attached my results for the benefit of newcomers who may not have played with it before.

Outputs are triangle and square, +/-5V in amplitude, running from 0.07Hz to 20.3Hz. On the low end, that's one cycle every 14 seconds. The output impedance of the square is about 1k; to make the triangle have the same impedance, just slap in a 1k series resistor.

You can find a very complete and understandable design analysis in Bernie Hutchens' Electronotes, of course. (What can't you find there?) What I've attached is a schem from the tinkering I did with the CircuitMaker 2000 SPICE software, and then included the actual results which match those predicted very closely. I'm willing to post the CircuitMaker design file if anyone else wants to play with it. Just shout.

This may not be the sexiest circuit around, but it sure is steadfast...and simple, when a manual triangle and square LFO is all you need. I think it's the best of its class.

Thomas Henry


LFO.pdf
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LFO schematic

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fonik



Joined: Jun 07, 2006
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PostPosted: Sun Jan 18, 2015 11:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

286:1 (sic!) Very Happy
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Thomas_Henry



Joined: Jul 24, 2009
Posts: 170
Location: N. Mankato, MN
Audio files: 3

PostPosted: Mon Jan 19, 2015 3:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

Okay, when rounded it's 20.3 / 0.07 = 290.

But that would be bragging.

TH
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