Quote from: Loudthud on August 26, 2024, 11:11:39 AMSide note: Figure 8 of Mr Elliot's article shows how a resistor is used to make a good logic low when diodes are used as an OR gate. You don't want CMOS inputs to be floating around causing circuits to intermittently malfunction... and they would seem to magically fix themselves when you tried to measure logic levels with a DVM which would pull the floating input low.

Again, I'm really grateful for any lessons I can learn. I can't stress that enough.

QuoteIt is unclear to me what you are trying to accomplish. Do you want to control 8 relays or loops with three foot-switches ?

Please refer to any circuits in RG Keen's or Mr Elliot's articles by the numbers of the illustrations in those articles.

As far as my last idea is concerned (SR latches and 4051 mux), I was referring to the diagram in Mr. Keen's article shown here. Later, upon further consideration, I realized that, in the configuration I had in mind, it wasn't necessary. What I came up with is on the diagram attached. A lot of parts have been omitted for clarity.

You can have up to 8 footswitches to control one 4051 chip. These switches are connected, through diodes, to the SET and RESET pins of three sections of the 4044 chip to force a "0" or "1" on the output of the correct section to make the 4051 connect its COMMON IN/OUT to the desired IN/OUT pin, as per the function table.
With the COMMON IN/OUT pin of the 4051 connected to V+, one could control transistors, for example. The collectors of those transistors could be connected to DIP switches which might serve as presets, in the most crude form, tying relay coils of individual effects loops to the collector of that transistor.
I think that this helps to tackle the following problems:
1. switch contact bounce
2. activating more than one channel after pressing more than one button / footswitch
3. excessive number of ICs
Of course it comes at the price of the number of diodes necessary, but you just can't have it all, can you?

Can you see what I mean now?

Quote from: Loudthud on August 26, 2024, 11:11:39 AMIt is unclear to me what you are trying to accomplish.

Ok, the fact that English is not my first language and that I'm a bit hyperactive, which will make me say something twice before I actually think about it, might have been contributing factors here. Sorry about that.

Let's go from the beginning.
Because, being a guitar player, I like different tones, over the years, I got myself a bunch of effects units to spice up the music I sometimes play. In order not to tap dance around my pedal boards, switching effects on and off, especially during a song, I started thinking about an effects loop switcher which would allow me to activate certain pedals and disengage others at the click of one footswitch.
There are, apparently, a number of ways to achieve that, including microcontrollers and CMOS digital logic. Some ideas have been provided by RG Keen and Rod Elliott in the articles I linked in the first post. Now, for a theoretical analysis, the number of pedals or channels is unimportant.

The point of this thread, initially, was to come up with a CMOS-based system which would prevent the activation of more than one channel if more than one switch were pressed. I think this goal has been achieved, but I'm still trying to refine the idea.

I'll get back to you later because now I've got a couple of things to take care of. Stay tuned.

Ok, I've got another idea.
For this one, I would use three SR flip-flops (CD4043 or 4044 perhaps) which could be set or reset in any combination possible through a network of diodes, and their outputs would be connected to the three data pins of the CD4051 mux which would steer a logic "1" to the inputs of some other device, like the 74HCT373 wired in a manner similar to (the same as?) that in R. G. Keen's article.

Theoretically, it would offer up to 8 channels. Moreover, it wouldn't care about contact bounce and pressing more than one footswitch at a time would simply activate one channel which gets SET first.

Does it sound doable or am I being overly optimistic?

Quote from: Loudthud on August 25, 2024, 08:01:40 AMI'm not the best person to explain this, and sometimes phrases such as this do not translate well into other languages, but I'll give it a try.

Thanks for taking the time to reply anyway. Besides being a hobbyist guitar player and gear builder, I'm an English-language geek, so I'm keen to learn new things.
I decided to use this idiom because, other than for expressing gratitude, I've seen it used in situations when the speaker was being sarcastic, and by the tone of their voice and the look on their face one could tell they were saying, 'You're being silly'. So, I wanted to laugh at myself a bit 
Have a good one.

Quote from: Loudthud on August 24, 2024, 04:03:33 PMI think you need a resistor to ground (...)

Well, bless my heart (am I using this phrase correctly, Loudthud? ), at first I thought you meant they should be from the output of the right-most inverters to ground, but then I brushed up on the diode OR gate thing and, boom, the cathodes of the diodes are tied to ground through a resistor in this configuration.
Again, thanks for pointing that out, sir.

Quote from: Loudthud on August 24, 2024, 04:03:33 PMI think you need a resistor to ground on each of the last inverters on the right so the output can go high.

Thanks for pointing it out. Are the resistors necessary when the inverters' outputs are tied to a CMOS chip's inputs?

I think I found it. Attached, you can find the diagram for my idea. It's based on a simple diode OR gate with inverters and it appears to be simpler and more effective than my previous idea. At least in my imagination
Could someone more knowledgeable than me take a look and tell me if it makes sense? Thanks in advance.

Quote from: Loudthud on August 23, 2024, 12:59:32 PMAnother subtle problem to solve is switch bouncing

If I were to use CMOS logic sensitive to contact bounce, I'd use a Schmitt-inverter-based circuit. I've tried it in the past with good results. Good for my needs, that is. Therefore, switch bounce isn't that much of an issue for me. Besides, the circuits implementing D-type flip-flops presented by Rod Elliott are immune from contact bounce, as he states in the article posted, so no biggie.

I had an idea that it might be useful to prioritize one input over another in some way and the circuit attached came to my mind. Two switches are presented, but perhaps it could be expanded further? So, as I see it, when one button is pressed, one HIGH signal is applied to one input on the controller of choice. When two buttons are pressed, the HIGH signal goes to the AND or NAND gate (depending on the component used in the blocking circuit) and breaks the connection between the bottom Schmitt inverter and its corresponding input, so only the top channel gets activated.
Does that make sense? Is it feasible?

QuoteI would probably use a microcontroller for this, and write a 20 line C program or something.

Yeah, and, quite likely, I'm going to do the same, but I like to learn, I like to know things.

I just had an idea. How about an AND gate at the output performing some kind of reset when two or more outputs change their states to high? On the other hand, this could be a nuisance with many channels, for instance, if the user stepped on switches 7 and 8 and channel 1 got switched on 🤔

Thanks. Now I understand the reason why you asked about the number of loops and channels I need.

Hi, Loudthud.
The number of loops and their combinations would be done elsewhere. What I'm after here is a circuit for selecting a setting, a patch, as I've called it. You might call them channels, I guess. For example,

I press switch A, output A on the CMOS device goes high (whilst turning the other outputs low) and engages, for example, a transistor connected to, for example, a DIP switch assigned to this particular patch where I've selected, for example, loops 1,3,and 5.
I press switch B, output B goes high (the rest goes low), its corresponding transistor switches on the loops connected to it through a DIP switch where I've selected loops 2, 4, and 6.
And so on.
Does that make sense?
What I'd like to know is how to make the device activate only one of the outputs if, for example, I step on footswitches A and B at the same time, which might happen if the switch box is tight and / or your boots are big.

Hi, everyone.
Firstly, I'd like to state that I wasn't sure where to start this topic because it's not exactly about an effects unit of any kind, but it is meant to switch effects, so here it is. If it's in the wrong place, I'd like to apologize and request that the Moderators move it somewhere proper. Thank you.

I've been thinking about building an effects switcher for my pedalboard to be able to turn on multiple pedals at the click of one footswitch. So, in search of ideas for selecting a given patch, I've found R. G. Keen's article at GeoFex and one by Rod Elliott, among others. Links here:
http://www.geofex.com/article_folders/fxswitchr/fxswitchr.htm
https://sound-au.com/project163.htm
Now, I'm wondering how to overcome the problem of accidentally engaging two (or possibly more) patches simultaneously if I wanted to build a CMOS-based controller. The way I understand R. G. Keen's design (schematic in question), if two footswitches are stomped on, two outputs of the 74HC373 go high, thus turning on two patches. The same is true for most designs provided by Rod Elliott (except the one built around the CD4017 Johnson counter and perhaps the one using SR latches).
I do understand that it'd be easier to use a microcontroller of sorts and make the code something along the lines of:

if input A is HIGH, output A is HIGH else LOW;

and duplicate it for other inputs.
However, I'd like to learn how to do that without turning to digital technology. I am also aware that it will add to the complexity of the circuit which will probably send me down digital path anyway. I'd like to learn nonetheless. Thanks for any suggestions, directions, and explanations.
Have a good one, everyone.
M.

Thanks for the info, Umlaut. I do appreciate it. It might come in handy for one of the projects I have in mind.
Have a good one.

Thanks, g1 (pentode control grid?  )
I'll measure the preamp's current draw and see how much or how little it is.
Have a good one.

@Umlaut
Hi, in practice, what's the maximum signal amplitude coming from that GIVE stage? Is there a limit?
Best regards,
M.