I want to drive the LED inside an optocoupler with the incoming guitar signal, but I'm having a little trouble. I'm very new to electronics, and at first I simply tried the basic LM386 amp with an LED and a 1k resistor on the output as opposed to a speaker. It seemed to work at first, and then slowly the LED stopped responding as drastically until it didn't respond at all. I then tried the 386 portion of the Uglyface schematic (http://experimentalistsanonymous.com/diy/Schematics/Fuzz%20and%20Fuzzy%20Noisemakers/Uglyface.gif), considering it is doing exactly what I'm trying to. The same thing seemed to happen. What am I doing wrong? Here (http://i.imgur.com/BC0BQ9g.jpg) is my schematic as it stands currently. Sorry for the noob questions.
We were all noobs sometime. As long as you're learning, it's good.
The reason the LED died is probably that LEDs do not like to be reverse biased. It slowly kills them for reverse currents to flow. They can only deal with a little more reverse voltage than forward voltage. Generally they're about 1.4 to 3.5V forward to get them to emit light, and maybe 5-7V reverse, which starts killing them. So putting AC on them is a death sentence.
You can do a couple of things. One is to put an ordinary silicon diode across the LED but in the reverse direction. That way, the reverse voltage is let flow by the silicon diode. There are others, but you're trying to do something there that already has limited voltages, so a reverse shunt diode is the first thing to try.
Is there a reason it works on the Uglyface schematic without the second diode? I will definitely try that when I get a chance regardless.
http://www.aronnelson.com/gallery/main.php/v/chickpea/sound2light2.jpg.html
with a 386.
Would the LEDs not be reversed biased in that case as well?
The "reverse bias" would be held to around .6v by the silicon diode. Voltage above that will turn the si diode on and slip right through.
Couldn't this be accomplished with a "modified" peak level indicator circuit?
Quote from: idy on February 24, 2016, 08:45:05 PM
The "reverse bias" would be held to around .6v by the silicon diode. Voltage above that will turn the si diode on and slip right through.
Oh! I actually meant in the layout deadastronaut posted.
> slowly the LED stopped responding
Did this LED actually die/dead/kaput/extinct ?
Or did it stop working while playing, but came back after a rest?
My suspicious is that a cap driving a single diode will always charge-down until current stops. If you let the charge bleed-off, it will work again for a while until it charges-down again. This is a key part of tube distortion (grid-block); and of several voltage multipliers.
If you don't want charge-down...
* Two diodes back-to-back will equalize things.
OR
* Add a heavy bleed resistor.
Both shown below.
(http://i.imgur.com/1ZVaBKK.gif)
Two LEDs is wasteful of your LED budget. Heavy bleeder is wasteful of your battery. In this case, neither "waste" is prohibitive.
Since you are driving 100 Ohms or 10 Ohms, the 2uFd cap seems small. It will also charge-down faster. For full bass in 100r, or short-bass in 10r, 100uFd is a fine value.
The second LED "could" be a plain diode. But the 0.6V versus 1.8V difference of voltage still leads to asymmetry and charge-down. It could be 3 or so plain diodes series (1.8V), but today three plain diodes cost as much as many basic LEDs. The second LED does not have to be exposed, it won't look different from the first one (but does give more light).
A bridge rectifier is another fix, but it adds 1.2V to the threshold voltage, and under 9V power you may not have that much swing. Anyway a Bridge is four diodes which is typically more cost than a cheap LED.
I would suggest Red, maybe Green, LEDs. Blue and White LEDs need more voltage, and a '386 on a 9V supply may not be able to get them lit well.
Quote from: kforte318 on February 24, 2016, 07:14:53 PM
I want to drive the LED inside an optocoupler with the incoming guitar signal...Sorry for the noob questions.
No apologies necessary! I was wondering what you intended to do with the LDR side of the photocoupler. Turning on an LED momentarily at an intensity that varies with your picking dynamics is what one kind of envelope generator circuit does. A familiar one is part of the Mutron filter. Check out Mark Hammer's article at GEOFEX to see what I'm talking about.
http://geofex.com/Article_Folders/ECFtech/ecftech.htm
Quote from: smallbearelec on February 25, 2016, 02:00:02 AM
I was wondering what you intended to do with the LDR side of the photocoupler.
I am trying to add a function to a tremolo that will modulate the rate and possibly depth based on picking dynamics. I'll definitely check that article out, thanks!
Quote from: PRR on February 25, 2016, 01:23:42 AM
Did this LED actually die/dead/kaput/extinct ?
Or did it stop working while playing, but came back after a rest?
That. It didn't burn out entirely, it just fizzled and would return to a working state after a minute or two. I thought it might have something to do with the cap! I'll test out your solutions and see how it goes. Thanks for the super detailed answer (also rad copy-paste diagram, took me a second to realize you hadn't just very accurately recreated my handwriting).
Why not go the envelope detector route.
Search for my ldr sweller. That will get you started with detectors
Quote from: Kipper4 on February 25, 2016, 08:40:16 AM
Why not go the envelope detector route.
Search for my ldr sweller. That will get you started with detectors
(http://i.imgur.com/XLObqiS.png)
Is this an accurate schematic? It looks like the original you posted in that thread had been deleted. Also, just for learning's sake, is what I am currently doing technically just a very crude envelope detector?
Quote from: PRR on February 25, 2016, 01:23:42 AM
OR
* Add a heavy bleed resistor.
The heavy bleed resistor got the circuit up and running! Thanks! However, I'm going to explore an actual envelope detector as Kipper suggested I think. For some reason, the guitar signal from the 386 seems to somehow be making it's way back into my main circuit... the modulated rate is working, but the very distorted guitar signal is constantly in the background.
Also if you look at replays 34 and 57 there's lots to choose from. Take note of what the guys noted too.
Maybe look at the nurse qaucky envelope detector.
Edit if you look at the schematic linked in this thread there's a similar envelope detector in the dod440 . At the top of the schematic.
http://www.diystompboxes.com/smfforum/index.php?topic=113385.0
Post 1
have you chosen a target tremolo yet?
I'll check me out Kipper. Thanks! duck_arse, I do have the tremolo up and running, yeah.
Which trem are you using though?
Quote from: Kipper4 on February 25, 2016, 10:45:01 AM
Which trem are you using though?
Not any specific one. I'm using an LFO I found a while back (I could dig it up later but am at work now) and a single bipolar transistor optocoupler VCA (also will have to wait until later to find it). I can post a full schematic later as well.
Quote from: kforte318 on February 25, 2016, 08:57:49 AM
Quote from: PRR on February 25, 2016, 01:23:42 AM
OR
* Add a heavy bleed resistor.
The heavy bleed resistor got the circuit up and running! Thanks! However, I'm going to explore an actual envelope detector as Kipper suggested I think. For some reason, the guitar signal from the 386 seems to somehow be making it's way back into my main circuit... the modulated rate is working, but the very distorted guitar signal is constantly in the background.
This is the same reason I am always suspicious of "asymmetrical" clipping arrangements. It completely doesn't work to use assymetrical diode pairs in a circuit like the Rat, and this is why. It might start asymetrical, but pretty quickly floats to be centered between the diode thresholds.
The bleed could be just proximity with other wires/components, but it could also be that you're pushing and pulling on the "ground" pretty hard. It's not supposed to move, but when I lived in New Orleans, I could feel the streetcar coming sometimes before I heard it.
Edit - Actually, as proud as I am of that streetcar thing, you're really pulling just as hard on the positive rail. It's quite possible that both are wiggling some. That old thing of careful decoupling. Put a BAC across the 386's power pins as physically close to the chip as possible. Might help to do the same with other amp stages in the circuit.
Oh man, that rail car analogy was so gooood. Well done. Forgive me, but what is a BAC?
Quote from: kforte318 on February 25, 2016, 12:19:56 PM
Oh man, that rail car analogy was so gooood. Well done. Forgive me, but what is a BAC?
Big Ass Cap
> return to a working state after a minute
This suggests the LED back-leakage is extremely low. A 2uFd e-cap would likely self-bleed almost that fast.
As you see, 10 Ohms makes the bleed really quick. Most of one cycle's charge is bled-off before the next cycle.
> is what I am currently doing technically just a very crude envelope detector?
On its own, it reproduces half-cycles directly.
An "envelope follower" normally filters the violent rectified wave into a smooth outline of the short-term average of the wave. To do this it needs some notion of how "fast" the envelope can change. Plucked strings need a rapid attack. If left to ring, the decay is always slow. If damped (or muted), the decay can be abrupt, so an envelope follower should not be too slow. We usually compromise with a small tail after an abrupt mute.
The raw LED "does work" if used to modulate a photo-resistor, because foto-Rs have a somewhat slow response to light on and a long decay after lights out. Different chemicals and cookings give different time constants. Different circuit impedances give different effective times on the same foto-R, because as R goes up the action gets slower.
@Kipper4
So I've been working with the Sweller circuit trying to derive the envelope detector from it.
(http://i.imgur.com/jyRTXGn.jpg)
I had it printed out to examine, and circled the bits I figured were important. Based on my ~intensive~ Wikipedia research, is the right-most circle the heart of the detector? What are the two left-most circles for (I assume input buffering and amplification of the signal before it gets to the detector)? Also, could I simply replace the Pad, Attack, and Decay pots with resistors if I didn't want controls for those parameters?
Good work.
Ic2a is as you say just a buffer for the coming signal.
You can leave out the pad and attack pots if you want and play with the decay outs value.
Then you can play with the values of the caps c4 and c5 to suit your needs.
Ic1b is the envelope detector and is driving the vactrol led too.
Hope this helps.
Probably a dumb question, but with the attack and decay pots wired as they are in that schematic, wouldn't they just act as resistors as opposed to variable resistors?
No dumb questions here.
They're wired as variable resistors. Since two of the lugs are tied.
Does that work that way?! This whole time I've been using one of the outside pins and the center pin, leaving the third disconnected.
Yer it works like that. Sure you can leave out the other but if one soldered lug fails you have no resistance at all, this way at least you have some resistance if not all.
Just a kinda protection wiring.
That make sense?
Edit.
I may have got my terminology wrong.
Here you go.....
http://www.allaboutcircuits.com/textbook/experiments/chpt-3/potentiometer-rheostat/
Yes it does! Good to know. Thanks again.
So I wired up the portion of the Sweller (@Kipper4), omitting the Pad and Attack pots entirely and replacing the Decay pot with a 1M resistor. The result seems to be the LED simply blinking along with the LFO and not reacting to the incoming guitar signal at all. Any ideas of what I may have done wrong?
EDIT: I replaced the 10n cap between the output of the first op-amp with a 100n cap, and it seems now to be responding slightly to the guitar (but still blinking along with the LFO when it's on instead of solely reacting to the guitar).
Take note it's an envelope detector ic1
Not an lfo .
Unless you have an lfo as well.
Note to I'm using TL072 for input buffer ic2
The envelope detector ic1is a lm358.
A lm741 ic will probably work well too for ic1
A fixed resistor instead of decay pot gives you no adjustment of how quick the led reacts.
Try a pot.
Change r5 to something much bigger 1M to 6M
I have an LFO elsewhere. Ah! That might be part of it though. I was using a TLO72 for both op-amps. Didn't notice that the detector was a 358.
I'll try and pot and maybe mess around some with some different R5 values. Mostly I always just want the LED to react as quickly as possible so I wasn't too worried about not having control over the parameter.
Righty Ho.
Remind me what the "driving an led with the guitar signal" was for.
I want to modulate the rate of an LFO with the guitar signal (strum the guitar, spike the rate). Basically just want to light up the LED in a vactrol.
I'm not even sure this is possible.
Show us where your up to ? Post a schematic please.
I'll have to do it in the morning, but can do! It was actually working with the Uglyface fragment and the heavy bleed resistor suggested by PRR, but I could hear the distorted guitar signal from the 386 in the output (which I did not want at all).
Google peak level indicator circuit.
You should be able to modify the circuit to do what you are trying to do. ;)
Quote from: kforte318 on February 29, 2016, 11:12:08 PM
I want to modulate the rate of an LFO with the guitar signal (strum the guitar, spike the rate). Basically just want to light up the LED in a vactrol.
ahhhhh....a guy did this very same thing with his modded version of the lightwah....i,ll see if i can find it....
(http://i.imgur.com/9AucFYZ.jpg)
Here's my full schematic. I'm not fantastic at drawing them and used a pen like an idiot, so let me know if I can clear anything up. I'll have an audio sample of this circuit up in a few.
EDIT: https://vimeo.com/157351753
I recorded this brief video with my phone sitting next to my amp. A little ways in I take the LDR out of series with the rate pot, and then I disconnect the LM 386 from power. You can pretty clearly hear the latter because all of the noise in the background drops away for the remainder of the video. Any idea how I can eliminate it altogether?
Hello guys.
I'm from Brazil and I have some doubts about something that I intend to do and that is very similar to what I read in this forum and, at the beginning, my biggest problem is to understand practically nothing of electronics. I built a fuzz pedal that can be seen at "http://tagboardeffects.blogspot.com.br/2013/02/red-fuzz.html". As per comments there on this page, I used a TL071 too but the LEDs didn't flash what is exactly what I wanted. When I started reading in this forum I thought that there could be another solution in which I do not have to discard the fuzz itself and that, by the way, is very good. I changed the diode LEDs (1N4138) and it still works fine. Being more clear and objective: I want to put an LED (or two) in the fuzz that flashes when I play (something similar to what can be seen in "https://www.youtube.com/watch?v=PH2uj9bWfM4&feature=youtu.be&t = 11 ").
Is there a solution in the fuzz itself (with some modification certainly) or can I add a small circuit as shown by the PRR a few pages back? Oh, and please, if anyone can help me I would ask it to be an explanation as if I were for a child of 5 years or less, well described in the smallest details because as I said, I understand little or nothing electronics ...
Right now, thank you folks.
And then folks?!?!?!? Someone ?
Egon! I don't think I can tell you like a five year old, but here's some stuff. always listen to what PRR says. we usually prefer/need to see the circuit diagram itself, because it is easier to read than someone's layout, but - your TL071 will be "strong" enough, should be strong enough, to drive the PRR LM386 circuit, and you will be the one to find out, one way or another.
on yr fuzz, the line/track/trace across named "Int 1" is where you would connect the point on PRR's named "IN". connect the +9V on each board together, and connect all the grounds together, obviously. you would probably try the LM386 on a breadboard before soldering it, wouldn't you?
are you familiar with earth, ground, common? and do you know pin 1 on an IC?
Part of the problem is that most of us want to see a schematic. To get a sense of the circuit.
Then we don't have to decipher the layout.
So to make it easier.
Here's an assumed schematic (because the direct link from the layout page didn't work).
Non inverting gain/clipper op amp ,some filtering with an N channel jfet buffer at the back end.
http://www.generalguitargadgets.com/pdf/ggg_dist_redfuzz_sc.pdf
I'll take a look when I get a mo.
Hello guys.
First of all I would like to thank your attention and tell the duck_arse that the 5 year old would be me ... :)
I understand that for you to look at a scheme is more important than a layout to be able to work on something. But for me it is just the opposite because of the limitation I have in relation to electronics. Layouts work like a copy and paste for me ... and 'op amp', 'filtering with an N channel jfet buffer' sounds to me as Greek or Japanese language ...
I am not belittling anything or anyone, just explaining my electronic knowledge So I'm sorry if there was any offense with my comments. Anyway, layouts are actually the best medium for my understanding ... it's kind of a cake recipe ...
To conclude, I just made the Sound 2 Light from Deaastronaut which can be seen at "http://www.aronnelson.com/gallery/main.php/v/chickpea/sound2light2.jpg.html" and that I thought I could "adapt" to my fuzz, and guess what .. It didn't works. :icon_cry:
I used LEDs in series, in parallel, white, red, yellow, etc ...
Well, for now this is it ...
Perhaps if I try to talk you through the schematic. You would recognise some of the componants etc and be able to follow.
I'd be willing to try if, you want to listen. It was all Greek to me too at one time and I still get it wrong plenty.
Maybe then we can look at debugging the sound to light.
Do you have a multimeter?
Quote.... tell the duck_arse that the 5 year old would be me ...
if you're only 5 years old, how come your typing is so good?
how about this - you present us with
the circuit, and the layout that matches it, and we can read
one and refer it to
the other, rather than having to decode the layout. and anyway, you'll be needing to learn circuits sooner or later.
Hello, gentlemen. I am here again.
I do not have a multimeter. And my reasonable writing in English is due to the google translator, :icon_smile:
I do not pretend to learn to read / interpret circuits and I also do not intend to buy equipment to use in this, because I just want to do 3 pedals (wah, fuzz, tremolo) for my use (with my guitar that I also did myself) and after that I probably will not come back to these tasks ...
Well, the Sound to Light finally worked with 1 and with 2 LEDs, red or white; when I used 2 I had to put them in parallel and not in series. They light weakly but light up as I play. Maybe the battery is already low ... I have to change it tomorrow. And I also think there was a "cold solder" in a ground wire of the little circuit (I do not know what is called "cold solder" in English).
Thanks and I should come back with other questions.
Hello guys.
Here I am again with my silly questions ...
Returning to the Sound to Light, I changed the battery and what happens now is that the LEDs are lit very strong and do not oscillate / flicker while I play and the sound distorts like a fuzz... For now I am testing only with the clean guitar sound.
When I come back with the previous battery (already well used) the LEDs flash weakly again ...
Still with the new battery, I tested using higher-value resistors (390R, 1K, 10K and even a 220K) and the brightness of the LEDs even decrease but they remain lit without blinking and the sound keeps distorting ...
Any idea of what can be happening? Thank you, Egon.
Hi.
I forgot that there was another question to ask: on a given pedal a ceramic capacitor of 470nF is used: since I am having difficulty finding this value, I ask if I can use 2 x 220nF in parallel?
There will be a slight difference of course (less than 10%), but would anyone have any idea how much this could affect the project? Thank you again, Egon.
The tolerance of a 470nF ceramic cap is likely more than the 30nF nominal difference you mention. It won't make a difference and you won't notice it.
Okay, Bluebunny.
I will then use 2 x 220nF because these I already have.
Thank you very much, Egon.
Well folks, I made a new experience: I have an AC / DC adapter that has outputs of 1.5 - 3 - 4.5 - 6 - 7.5 - 9 - 12 Volts. I decided to use it starting with output = 1.5V and the LEDs glowed intensely without blinking and the sound came out clean. I used the 3V output and the LEDs continued to glow brightly and the sound began to distort. The same happened when I used 4.5V with increased distortion ... I stopped there for fear of "burning" the IC or the LEDs or anything else ...
I am reporting these details just so that if anyone is willing to help get more information of what is happening and reminding everyone that I am using the Sound to Light layout of Deadastronaut "http://www.aronnelson.com/gallery/main.php /v/chickpea/sound2light2.jpg.html ".
Thanks.
Sorry, the link is "http://www.aronnelson.com/gallery/main.php/v/chickpea/sound2light2.jpg.html".