Digital I/O Recall

Hi :slight_smile:

I want to make a box with 50 inputs and 50 outputs that essentially operate as independent non directional "thru" paths that can handle up to 30 volts RMS p2p, like a simple set of wires but reconfigurable digitally. No relays.

The interface must work on rotary encoders that matches "ports" in any configuration the user wants that are viewable on a screen. These configurations must be recallable at the push of a button.

example:
1 to 51
2 to 52
9 to 99

There is more to this idea, but this is my starting point. Help an Arduino newb? I have a background in component level tech work, but not in digital electronics. I'm pretty good with analog circuitry :slight_smile:

Cheers,

operate as independent non directional "thru" paths that can handle up to 30 volts RMS p2p, like a simple set of wires but reconfigurable digitally.

So 30V RMS is +42V and -42V or 84V peak to peak.

This is not a beginners project and I feel it is way too big for you. What sort of current do you want to switch? That is often a big crunch. Most electronics will not run at these sorts of voltages, you are in expensive territory.
I would certainly not try and build such a system myself.

Basically this sort of things is called a Crossbar switch and would cost you several thousands of $ to make.

Imagine if you could get a switch element for $1, a highly unlikely prospect, then the project would cost you at least $2500.

Perhaps you should solve the "XY problem" here first.

Grumpy_Mike:
So 30V RMS is +42V and -42V or 84V peak to peak.

This is not a beginners project and I feel it is way too big for you. What sort of current do you want to switch? That is often a big crunch. Most electronics will not run at these sorts of voltages, you are in expensive territory.
I would certainly not try and build such a system myself.

Basically this sort of things is called a Crossbar switch and would cost you several thousands of $ to make.

Imagine if you could get a switch element for $1, a highly unlikely prospect, then the project would cost you at least $2500.

RMS is just 0.707 times whatever the other p2p is... 42 sounds right depending on where the starting point was. Who said we were starting with only the up or down cycle? Thanks for taking the time to do that though. I mean 42VAC p2p if thats easier for you.

There are no digital switching chips that can handle 30V? low current, milli amps..

We're talking about switching audio here.. synthesizers that max out at 10 V.. the 30 is a precaution to help with spikes. Lots of companies seem to be making digital switching matrixes.

Lets have a look at that beginners XY problem : )

I think your XY problem is mainly negative thinking in this case.

Can anyone point me in the direction of a project that does some simple port switching?

buildafriend:
We're talking about switching audio here.. synthesizers that max out at 10 V.. the 30 is a precaution to help with spikes. Lots of companies seem to be making digital switching matrixes.

Any other details you left out of the OP?

Want real help and not the runaround? There are many of us who can help, just waiting for you to fill in all the details. But I'm not going to get into the scrum trying to figure out what you're building. Just come out with it or keep dealing with what you're getting. Be detailed and you'll get better help from different folks. Keep it vague and you'll just get what you're getting.

I mean 42VAC p2p if thats easier for you.

No that is 42V peak, it would be 84V peak to peak.

42 sounds right depending on where the starting point was. Who said we were starting with only the up or down cycle?

That is just a nonsense. What is a starting point? Do you know any AC theory?

There are no digital switching chips that can handle 30V? low current, milli amps..

As we have established you need more than that, and this is the first time you have mentioned low current, even analogue switches at 30V are quite rare and expensive things.

We're talking about switching audio here.. synthesizers that max out at 10 V.

Nice of you to let us know.

the 30 is a precaution to help with spikes.

That is rubbish. You are backing off quite a bit from what you initially said.

We can only go off the information you provide we do not read minds.

Lots of companies seem to be making digital switching matrixes.

If you can find a 50 by 50 crossbar switch I would be happy to look at the link and tell you why this is different from what you asked for.

So this is an X-Y problem after all.

Im not here to get technical about your advice Mike :slight_smile:

What details seem missing to you? I’ll explain whatever else you need!

buildafriend:
What details seem missing to you? I’ll explain whatever else you need!

No, you explain everything. I don't want to have to try to guess at anything. I don't want to have to go through a process of asking a bunch of question to try to figure out what you are doing. Either just explain the whole thing in detail or keep dealing with Mike. Give me enough detail that I could build one just like it here if I wanted exactly like what you want and test it and get exactly the same results.

Start by telling me what it is supposed to do. Not technical, no "hook this signal to that blah blah. Tell me what it is supposed to do, this thing will take sounds from my trumpet and play them on a drum machine. I hope I can accomplish this by... EXACTLY what signals you have and where they come from. Things like that. I don't want to waste time on someone vaguely half-assed explaining and then once I've put in some effort suddenly there's one more requirement or whatever. Just get it ALL out there.

buildafriend:
Im not here to get technical about your advice

Maybe, but this technicality is very important, it determines if your project is at all feasible.
We started with a requirement to switch 30V RMS, which I said translates into an 82V Peak to Peak signal. That sort of thing is very difficult to do. It turns out you actually want to a 10V AC signal but we have not established if the 10V is RMS, Peak or Peak to Peak. Any electronic switch has to be able to cope with the Peak to Peak value of the voltage you are going to switch. Talk of wanting an overhead to handle spikes is just a nonsense.

Next is the size of this cross bar switch a 50 by 50 matrix is very big. It means you have to generate 2500 output signals, one to drive each of the switches. That in itself is a major project. Suppose you can get a chip that will expand the outputs to give you 16 extra pins, then you will need 157 of such chips.

Then you have the signal switches themselves. I might have found a IC switch that would switch +/- 15V, it contains 4 switches, so that means you need 625 of them. So already your system has 782 ICs, I don't think this is feasible, so is it possible to reduce the size of your system?

Delta_G is spot on, we need to know a lot more about your needs rather than your wants and we need to know what is feeding this signals and where they are going to. You said:-

There is more to this idea, but this is my starting point

We need to know what this is because this could be a dead end. It is clear that the present requirements are way over the top in terms of practicality and also budget. Do you have a budget? What is it?

Brief research indicates he had the same problem last project. :astonished:

Okay I'll put this as simple as possible. I'm trying to make a device that memorizes synth patches similar to the device below but one that can handle much more I/O than that. As for the how the device works TBH I really don't care as long as I can build it, make it open source, and it's a user friendly device for the operator/musician can use for patching and recall. Do you want me to design a front panel so we can work from the front panel down?

I simply figured it would be nice to have more power handling. If that's prohibitive lets forget it and stick with whatever does the job.

Mike is right about RMS. I needed to glance back over that one.

Similar to this - but more I/O. Lets forget making it any more complicated than that for now.

https://www.ericasynths.lv/shop/eurorack-modules/by-series/basic-series/matrix-mixer/

Input signal level

up to 20 Vptp

Inputs

10

Outputs

8

Signal mode

both audio and CV

Mixer GAIN

1

Resistive touchscreen

3,2”

Internal clock

20-320 BPM

Power supply

bipolar +-12V , eurorack standard

Does anything still feel vague?

Delta_G:
Start by telling me what it is supposed to do. Not technical, no "hook this signal to that blah blah. Tell me what it is supposed to do, this thing will take sounds from my trumpet and play them on a drum machine. I hope I can accomplish this by... EXACTLY what signals you have and where they come from. Things like that. I don't want to waste time on someone vaguely half-assed explaining and then once I've put in some effort suddenly there's one more requirement or whatever. Just get it ALL out there.

Does my above post help with this?

see this pic? at the top of this page?

I want to make all of that wiring go to one box that is control unit for patching it all.

Here is an archaic version

Similar to this - but more I/O. Lets forget making it any more complicated than that for now.
https://www.ericasynths.lv/shop/eurorack-modules/by-series/basic-series/matrix-mixer/

So how much more I/O? The complexity and the price goes up as the number of inputs times the number outputs increases. That link shows an out of stock product but a web search shows this "small" cross bar switch as costing €447. Are you expecting to be able to recreate a one off of this than less than that?

http://www.electronicbeats.net/the-feed/eurorack-modular-synth-laptop-free/
I want to make all of that wiring go to one box that is control unit for patching it all.

No way Jose.

What you are fighting here is that:-

  1. They have made many prototypes
  2. It has been tested and worked on by experts, my guess is that it would have taken about 5 man years to develop and bring to market.
  3. They have the ability to buy components in bulk at a fraction of the price that you can.

It is a very ambitious project just to replicate what they have done, let alone take it further. As I asked, what is your budget?

I think asking someone to design it for you is an impossible ask.

You might want to look more at the open synth forums and ask about this there.

Good luck with your project.

Let's say budget is 2k for prototyping.

Target is 50 in and 50 out.. but that's a little flexible.

Do we all agree that a crossbar topology is a good solution?

Do we all agree that a crossbar topology is a good solution?

I think it is the only solution that does not involve mechanical connections.

Target is 50 in and 50 out.. but that's a little flexible.

I would not go bigger than 20 by 20, scaling up in electronics is not easy. Just like going from baking bread in your own kitchen for you, to making bread for the whole town.

In fact I would start with just a 4 by 4 to make sure the rest of the circuitry is sound.

buildafriend:
Input signal level
up to 20 Vptp

OK, so we finally recognise something that is within the bounds of standard op-amps such as the old LM741, making it possible.

If you strictly restrict your operating voltages to 15 V peak-to-peak, you can use CMOS devices such as the CD4051.

And if you consider instead, using "patch-cords" instead of a crossbar, then it is probably somewhat manageable; four CD4051s for example, make a 16 to 16 patch-cord, eight for a 32 to 32. You just need to determine how many patch cords you actually need.

I thought you could use this https://uk.farnell.com/vishay/dg445dy-e3/switch-analog-quad-spst-soic16/dp/1102506

Grumpy_Mike:
I thought you could use this https://uk.farnell.com/vishay/dg445dy-e3/switch-analog-quad-spst-soic16/dp/1102506

Except that is only four switches, you are going to want an awful lot of them.

Farnell off-line just now. :astonished:

This device - a 16 to 1 multiplexer rated for up to 30 V peak-to-peak - would be more practical - depending of course on price and availability but hey, we have already sorted out; money no worry.

depending of course on price

Not cheap.

https://www.mouser.co.uk/ProductDetail/Renesas-Intersil/HI3-0506A-5Z?qs=%2Fha2pyFadugrzf8fEs83WFCIzfO%2FCUv02hBwK%2FfsZo4%3D

And how are you going to configure more that an 16 by 16 cross bar switch without resorting to having the path go through multiple multiplexers. So for a 32 by 32 switch you would need 64 of these chips plus 32 two input multiplexers. That is £687.36 worth Hi-506. I suspect extending to 50 by 50 will break the budget.

EDIT:- Sorry I miscounted you would need 128 of the Hi-506 chips, still you get the better +100 price bringing the cost up to £1210.88 for just these multiplexers