Uglyface LFO LED doesn't go fully dark

[cox]

HI! I'm building this LFO as a standalone unit to fit some other purposes.

https://postlmg.cc/34QxSf0D

The LED blinks, but it doesn't behave how I would expect: It doesn't swing from fully dark to fully bright. I have everything on a breadboard and I don't have all the knowledge on my side to pick a starting point to debug this thing.

So, is It supposed to swing from dark to bright? If it is, where should I start searching for problems?

Thanks!

[strungout]

A full schemtic would be useful. On the one you posted, there isn't any LED, so we can't really say anything about it, how it's connected, etc. The LED CAN go totally off to totally on. Usually, you adjust just how much it swings with the depth control (maybe it's that 'sensitivity' control?)

This could be of use to you: https://www.diystompboxes.com/smfforum/index.php?topic=124587.msg1183798#msg1183798

[cox]

Frank, Thank you so much for your reply!

Sorry, this is the schematic I'm following



I omitted the sens. pot to see how it would work with it 'on' & 'off' - I also put a 1k resistor in between the LED and the other 1k one just to see how it would work and it works as expected (i think), the LED won't swing so hard as without the 1k resistor before it.

Thanks for the resources shared, I've seen them before! I will follow your LFO design once I see I'm not able to get this to work. I was just trying to keep it real simple, low parts count and without losing the hability for ramp up/down.

And the LED would be used to 'drive' an LDR.

Thanks once again!
Luís

[bartimaeus]

did you try measuring the range of the voltage and current output from the lfo? with simple lfos like this they often have a somewhat limited range.

generally for something like this i prefer to use the output of the lfo to control a transistor, with the transistor controlling the led brightness. that usually solves any limitations from using the lfo to directly control an led or vactrol.

[strungout]

Hey,

just to make sure I don't take credit for someone else's work, the LFO I used is from the 4ms Tremulus Lune. Not my design.

So I breadboarded the LFO. To me, it works as expected. With a depth control you could get to a 'choppy' sound (i.e, it would go almost all the way dark) but if you just want a smooth transistion, this will work. I suggest you try it within the ugly face and see if that's the 'wiggle' you're looking for. When it comes to DIY optos, there's a LOT of trial and error and learning. But it's not as complicated as it seems.

Here's an example of what bartimaeus is saying:
deadastronaut'S Lightwah.

(that's the only version I have... Btw, note that the LDR in the dark/light section is connected to the Base of the transistor and then to ground. The Emitter of the transistor goes to ground too. But you don't need it for your purposes). This LFO works very well. Also, notice that the 'depth' control is connected to the LDR, not to the LFO, as some designs (like the Lune does).

You're already doing that so, keep experimenting!