Help me solve this situation; how would you do it?

[ShadSunsCrash]

Situation:

Im building a Chasm Reverb.

The Chasm Reverb has an auto oscillate feature that is triggered by selecting one of two resistors in a feedback loop (select 47k and you get oscillations, select 100K and the Oscillations can not build).

Im using an on on toggle for the oscillation switch which will select which resistor is in circuit. This is a stock feature.

But ive also decided ill be using a momentary footswitch as well that will also turn on (or off) oscillations.

I thought about it and decided the best way to go about this would be to have the momentary switch add a resistor in series with the 47k which will raise the resistance to about 100k. And another pole on the momentary will add another 100k to the 100k resistor but this time in parallel bringing the resistance down to about 50k (i might tweak the values to get closer to 47k if it turns out to be worth the extra effort).

So all of that is figured out and i have no problems executing this modification. So a quick recap.

The pedal will have a toggle to turn on and off oscillations AND a momentary switch that will turn oscillations ON when the toggle has the oscillations OFF and the momentary switch will turn the oscillations OFF when the toggle has the oscillations selected to be ON. It will accomplish this by adding resistors to the 47k and 100k that will raise/diminish those two resistors and in effect swap their values momentarily.


ACTUAL PROBLEM:
(That im working on solving)

I want an LED indicator that will be on when the oscillations are on and off when the oscillations are off regardless of which switch is acting upon them. Ive worked it out on paper a few times and each time find myself up against a dead end.

Im open to any suggestions and keep in mind im happy increasing the available pole count of both switches (the toggle and the momentary). Im also open to building a simple circuit possibly with JFETs? Ive used JFETs as switches before but only in very simple single sided operation. But the problem with using JFETs for this is i feel like it woul get overly complicated quickly. Who knows? Maybe there is an even simpler solution im just overlooking?

Anyways thanks for your suggestions on this one, hopefully ill come away from it having learned something new!

[kaycee]

I don't see why you'd need an indicator for the momentary switch? If your holding it down,it's on (or off). Easy to add poles to the toggle, even use a dual colour LED (and forget which colour means what  ).

[jonfoote]

sounds like you could use something similar to 2 way switching like you'd use to control a lightbulb from 2 different switches.

https://www.electricaltechnology.org/2012/11/how-to-control-one-lamp-from-three.html

Double up the switches to dpdt and use one half for the resistor and the other for the LED.

[bluebunny]

I'm not convinced of the musical application of oscillation controlled by a toggle switch. Once it starts oscillating, there's no going back, other than stooping to switch it off. Not elegant mid-song. I'd go with the momentary footswitch, in which case no indicator needed, as kaycee points out. But just my opinion... 

[niektb]

I'm not convinced of the musical application of oscillation controlled by a toggle switch. Once it starts oscillating, there's no going back, other than stooping to switch it off. Not elegant mid-song. I'd go with the momentary footswitch, in which case no indicator needed, as kaycee points out. But just my opinion... 

Hmmm not per se, depends on how it fades... when you put a limiter on the feedback (clipping diodes f.e.) and pull the mix down low, you can create a drone underneath your playing. Might be great to have during a verse f.e. and then switch it off during a more forward chorus? Just some random idea...

[deadastronaut]

if i understand correctly...

try a momentary dpdt.

one side for the osc switching, other side for the leds.

o        o ---+led  gnd


o        0----4.7k resistor ---9v+.


o        o ---+led gnd

[MrStab]

So either:

• Detect resistance. AFAIK not too easy in analogue, with such a small difference.
• Detect audio characteristic of this feedback (you may get lucky and there could be some ultrasonic artefact).
• Have a separate set of poles on both switches, which effectively feed into an OR gate of sorts.

It seems excessive, convoluted and unlikely. Count me in!

[amptramp]

I think we have finally found a use for a burst box.  Just connect it to a 100K resistor and switch it in parallel with the 100K resistor that is already there.

[ShadSunsCrash]

I don't see why you'd need an indicator for the momentary switch? If your holding it down,it's on (or off). Easy to add poles to the toggle, even use a dual colour LED (and forget which colour means what  ).

Who said anything about NEED lololol. This is purely a WANT thing. Ive got a symmetrical layout planned and the 2nd led just fits. But you're absolutely correct. Its utterly pointless, its just a matter of wanting to do it so i learned to solve the problem and say i did it lol. And remain symmetrical of course! Plus with the LED for the momentary switch it will show other users whether it is turning the oscillations on or off depending on the toggle switches position making the design more intuitive.

Im going to go with the Four knob layout for this one. I drew up a layout for a five knob version also, (Five knob version is not to scale an neither are the final draft which i do in INKscape) it was going to be for a BTDR 3H Chasm reverb. Again, completely unnecessary but theres no rules here and i tend to have a field day when there are no rules. So the aforementioned symmetrical LEDs are as such cause with only one placed in the center it would look like i was lining up bowling pins which is certainly not the look im after lol. And i always do leds next to the footswitch where they would be even more pointless with a momentary switch. Which is what brought me to the opinion that two symmetrical LED's would be best for this build.

[ShadSunsCrash]

I'm not convinced of the musical application of oscillation controlled by a toggle switch. Once it starts oscillating, there's no going back, other than stooping to switch it off. Not elegant mid-song. I'd go with the momentary footswitch, in which case no indicator needed, as kaycee points out. But just my opinion... 

I tend to agree which is partly why i want the toggle AND the momentary. That way Oscillations can be turned ON when the toggle is OFF and turned OFF when the toggle is set to ON. This is why an LED would be ideal since its intuitive and shows which state the toggle is in and what the momentary footswitch is actually doing i.e. turning oscillations on or off.

[ShadSunsCrash]

if i understand correctly...

try a momentary dpdt.

one side for the osc switching, other side for the leds.

o        o ---+led  gnd


o        0----4.7k resistor ---9v+.


o        o ---+led gnd

Hey Rob! Thanks again for the PCB.

I probably didnt explain myself very well. Ill try again. So i understand how to trigger and LED when the footswitch is pressed but I want to have a toggle AND a momentary which i also know how to do. What it will be doing is turning on oscillations when the toggle is off and turning them off when the OSC toggle is on. Thats where the problem comes into play. Id like it so the led for oscillations is lit when the oscillations are on, and turned off when the oscillations are off regardless of whether they are on or off momentarily or latched.

Boy, i probably just made it worse. Hopefully im not making even less sense lol. Even i dont understand myself sometimes smh!

[ShadSunsCrash]

So either:

• Detect resistance. AFAIK not too easy in analogue, with such a small difference.
• Detect audio characteristic of this feedback (you may get lucky and there could be some ultrasonic artefact).
• Have a separate set of poles on both switches, which effectively feed into an OR gate of sorts.

It seems excessive, convoluted and unlikely. Count me in!

Brother you are on the same wavelength as me with this one. I was thinking the same things. I started down the rabbit hole trying to track resistance and quickly realized it just wasnt likely the best solution. But i will say detecting an Audio characteristic/artifact isnt something i even thought of but i love the "outside the box" thinking lol!

In the end i think im just going to have to dumb it down for now. Meaning i think ill just build it to trigger the LED anytime the Momentary is triggered and label the LED "OSC Stop/Start" and label the toggle "OSC ON/OFF". I think the working state will be pretty obvious to anyone using the pedal but i just thought it would be cool to track the actual state of the oscillations some way so the LED would just indicate whether oscillations were on regardless of whether they were momentarily on or latched on. I try to make my pedals as intuitive as possible and sometimes that just means simplifying the problem rather than looking for a simpler solution to a more complex problem.

Thanks for the reply! It helped convince me further that theres probably not some obviously simple solution ive overlooked since i tend to overthink EVERYTHING!

[ShadSunsCrash]

I think we have finally found a use for a burst box.  Just connect it to a 100K resistor and switch it in parallel with the 100K resistor that is already there.

This ive actually already planned on doing, in fact i wrote Rob about doing that week before last lol. I figure id do the 100k in parallel and the 47k in series on a momentary so that the momentary footswitch acts as a "Start/Stop OSC". The problem i was still trying to solve is how to trigger the LED regardless of whether oscillations are on momentarily or latched on. So after careful consideration ive decided to dumb it down a bit. So instead ill just have the momentary footswitch LED turn on anytime its engaged but ill label it "OSC Start/Stop" and then label the toggle "OSC ON/OFF".

I think that should keep things pretty intuitive still. But ill still be searching for a solution that allows me to have the LED trigger regardless of how oscillations are triggered.

Im not familiar with what you meant by "burst box". Hell maybe you did understand my original problem and I just misunderstood your response. If thats the case please let me know! Any suggestion i haven't thought of is a chance to pick up something new that might help later if not now.

[dschwartz]

Connect a simple spst momentary to 9v into a cd4053 switch (or a relay), and connect the LED to the "control" pin.