Simple LFO schematics?!?

Lorenzo · Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy

hallo,
I'm looking for a simple (... but sweet) LFO
I found some 555 schematics ... but
I would like to run it +-12 or +-15
could you link me an LFO schematics ?

thanks!

fonik · Posted: Thu Sep 17, 2009 4:33 am Post subject:

http://www.musicfromouterspace.com/analogsynth/NewAugustRampLFO.html

Lorenzo · Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy

Gulp... only 5 minutes... You win the price... Very Happy

Thanks

Dave Kendall · Posted: Thu Sep 17, 2009 7:26 am Post subject:

You might also be interested in this.....

http://www.cgs.synth.net/modules/pic/schem_cgs58_lfo.gif

It's a simple dual manual LFO. (no Voltage control) and is great for modulation duties.

The pic below shows a cut-down version for breadboarding if you just want pulse, and a variable saw to TRI to Ramp wave. Only a dual OPamp (TL072) is needed for a single LFO.

Changing the 47n capacitor allows for a "Range" switch to get ultra-slow to quite fast - see fonik's details here

http://modular.fonik.de/files/CGS_LFO_mod.jpg
which refer to the actual CGS board!

Ken's PCB adds other goodies too......

cheers,
Dave

simple osc2.jpg

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Tim Servo · Posted: Thu Sep 17, 2009 9:58 pm Post subject:

Several different LFO schemos here:

http://electro-music.com/forum/topic-32372.html

Including my 8K LFO and a couple of different waveshapers (I mention it because it was my own design and it's kinda nifty) Wink

Tim (I like LFOs) Servo

Lorenzo · Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy

Hallo,
thank you very much for all your kindly reply.

everything seems to be very interesting, but I thougt to build the MFOS LFO.
I just recieve an ADSR PCB from MFOS, but I forgot to order a LFO too...

so... I'm very new in electronics, anyway I try to extract from the schematics a DIY PCB. Is someone so kind to see if it is allright??
Thank you very much!

http://img121.imageshack.us/i/lfodiypcb.jpg/

LFO DIY PCB.jpg

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MFOS' LFO DIY PCB

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thundarr · Posted: Tue Sep 22, 2009 9:20 am Post subject:

Yeah, that should work fine... From what I can see that looks like a relaxation oscillator, switch S1 is your ramp/sawtooth selection switch, R5 is your frequency pot, and the chip is a dual op-amp (TL082 or similar)

Not entirely sure what switch S2 does, it changes the capacitance on the feedback loop of one of the op-amps, probably for signal shaping, I'd imagine.

It would help if we knew the values for the parts, but that circuit should oscillate at least.

EDIT: It's a very similar circuit to the one Dave Kendall has posted above.

thundarr · Posted: Tue Sep 22, 2009 9:33 am Post subject:

Ahh, it's Ray's ramp and sawtooth LFO!

Yeah, that looks just right Smile

Lorenzo · Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy

Lorenzo · Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

I think yes. They decide the direction of the saw, blocking the positive or the negative. By the way you can try it.

Regards Lorenzo.

Lorenzo · Joined: Nov 09, 2008 Posts: 375 Location: Trieste - Italy

ogg · Joined: Sep 30, 2009 Posts: 10 Location: UK

slacker · Posted: Sat Oct 03, 2009 7:17 am Post subject:

I've just had a quick look at it and it's a simulator problem. I'm not an expert on simulators but I think the problem is caused by them using ideal components, and the fact that it's not simulating the effect of actually turning the power on. If you look at the voltages the output of the integrator is at 0 volts so the + input of the Schmitt is as well. The Schmitt will only do what it is supposed to if the voltage on it's 2 inputs are different, as they are both 0 volts, because the - input is connected to ground it won't do anything.
In the real world the effect of powering the circuit up plus things like the integrator capacitor charging up would cause the circuit to start up.
Something like that anyway, someone else can probably give a better explanation.

You can can make this circuit work by disconnecting the negative input of the schmitt trigger from ground and connecting it to a 1volt voltage source instead. That way when the simulation starts the 2 inputs are at different voltages so the Schmitt will work.

Nice site by the way, I've seen that falstad thing before but I didn't realise you could make your own circuits with it.

ogg · Joined: Sep 30, 2009 Posts: 10 Location: UK

Thank you

I've added your fix to the circuit and put it on the site.

Tim Servo

MC1495 · Joined: Mar 24, 2009 Posts: 19 Location: baltimore

Regarding the simple LFO schematic at the top of the page (simple osc2.jpg - I think the first time I saw this was Ian Fritz's schematic for ElectroNotes?) -

Has anyone given any thought to making the symmetry adjustable by voltage control? The only solution I can come up with is some sort of cross-fading circuit - but maybe there is something more direct? ..

JovianPyx · Posted: Thu Aug 11, 2011 5:44 pm Post subject:

Here is a simple CMOS thing:

http://jovianpyx.dyndns.org:8080/public/fatman/4069_lfo.html

Triangle-ish. This was designed for a Fatman, but can be adapted easily for whatever.