retrofitting an auto-mute volume control?

To start off, I'm not looking for a specific design, though of course I will be very happy for any such attempts. I'd like some thoughts about approaches or problems I may need to consider. I'd be happy to then expose some design I come up with, to criticism.

I need an auto-mute circuit that I can use to retrofit devices that provide an amplified audio output to a speaker or speaker pair. These include television sets which use UP/DOWN buttons to set volume all the way to resistor-based knobs and wheels that set volume.

I could consider not "getting everything" and instead just focusing only on those devices which use a resistor to control the volume, interceding at that point (using the existing control but adding a circuit around it.) In that case, the circuit would need to behave the same regardless of which resistive 'end' was used to set the highest volume. I'd like to handle TV sets that use UP/DOWN buttons, too. But even _some_ solutions are better than none.

By 'retrofit' I mean that I cannot add new control systems to existing ones by drilling holes and making the operation more complex to handle

-- the operation must be fully automatic and set by me _before_ I open up the units and insert the circuit, without having to create any external access holes or buttons, etc.

My daughter has grand mal seizures that my wife and I need to hear the beginnings of. My daughter loves to turn on stereo systems and music boxes, quite loud at times. She enjoys listening and often has her computer software playing something loud while having a CD player playing something else in the same room, while still something else is playing on a CD player in the next room, as well. We don't want to take that away from her, but it also makes for a noisy environment which can easily mask our ability to detect a seizure as early as we'd like to. The results of our missing the early sounds of a seizure event could potentially lead to broken arms, or even death in an extreme case. So this can have very important consequences.

We've used timers on the power plugs. But besides the fact that she moves things around from place to place if it "doesn't work" from her point of view, using a timer greatly complicates our own life. She needs to have the ability to initiate the operation by using controls that already exist on the device. (She is 25 years old, but operates much like a 4 year old. She can learn some things, like how to turn the volume control knob, but using timer boxes greatly complicates operation and thus greatly complicates both her and our lives.)

What I need is something that doesn't increase the complexity of her use of the device. She simply needs to learn to "adjust the volume" as she always does to cause the mute operation to cease, instantly. But that action should initiate the start of a new timing cycle. The auto-mute effect needs to take place after about 10 minutes of use, but I'd like to be able to set that range from perhaps 1 minute to 15 minutes. That said, to be completely honest about it, I could live with a fixed 10-minute delay.

The power source is an issue. These devices I'd modify _do_, of course, have internal power supplies and I could scarf around to find something to attach to, of course. How the ground will relate to the speakers, I don't know. It may depend on the device. The speaker outputs may even be galvanically isolated. Best would be that energy is derived from the sound system's own delivered power to the speakers, so that it's 'universal' in that regard. This would save me from replacing batteries or having to make custom designs for each and every situation's internal supply modifications. (While the voltage is building up in such a case, though, I'd like the unpowered circuit situation to be 'unmuted.') But battery powered, if necessary, is acceptable if I don't have to replace them more often than once every few months and so long as I'm able to fit the battery system inside (in some cases, that will be 'hard'.)

What would work best for her is that if she 'fiddles' with the volume control, the mute operation ceases and the timer starts.

This needs to work on CD and karaoke players, stereo and mono amplifiers, TVs, etc. Almost all are wall-plug powered. Not all, though. Some use multiple D-cells ('boom boxes') or allow an 'either-or' operation, using batteries if unplugged from the wall.

I've only just begun to think about this and my own limitations in experience are suddenly in evidence to me. My first thought would only work on the resistive type controls, would use a micro to monitor the value (ADC) and then control a digital POT I select. It would need power but I could use an MSP430 to mitigate that problem, using a small CR2025 or CR2032 which would last quite a while. (The timing requirement of minutes, alone, almost forces me to think in terms of a micro, though I can think of a few analog circuits using a cap and mosfet that would handle such times.) I would probably need custom programming, a tweak for the input gain perhaps, and perhaps a different digital POT for each unit I modified. But at least I can see how to handle that.

Thoughts and criticisms meant constructively are appreciated.

Jon

Reply to
Jon Kirwan
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THAT Corporation makes nice AGC/MUTE chips with compression/expansion/ log detection.

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Steve

Reply to
osr

This is not a technical problem. It can't be solved by any technical means.

VLV

Reply to
Vladimir Vassilevsky

I'm not sure what problem _you_ are talking about. The question _I_ asked can be addressed from a technical perspective, at least in piecewise fashion. If you are referring to the larger problem of life itself and the issues we as a family face, I wasn't asking for a solution to that.

Jon

Reply to
Jon Kirwan

A little too 'jazzy' a web page, for one thing. I'd be fine just building a micro to handle the ADC-to-digipot thing, so if the offering is more expensive or has a longer learning curve for someone used to doing embedded stuff, I may pass. At least, I'd know I'd get exactly what I needed, doing it by hand.

Anything there you wanted to draw my attention towards?

Jon

Reply to
Jon Kirwan

Not sure if it helps....

On the cd player at least, power it via one of those pneumatic timer switches often used to control stairwell lights in apartment blocks. You can adjust the time delay on them. Not sure of the run time range. Nice & simple.

Use to enable power or audio path. Just press the button in and the thing will run for the time set.

something like:

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Reply to
Nik Rim

That violates what I was talking about earlier. I'd like to avoid complicating what is already enough for her to learn to use and the units need to remain powered (the computer still running, for example, and not shut down), which is why I was looking for a timed 'mute' capability and not a complete power-off function. I've got a box of something almost exactly like those. (A few have been applied elsewhere, where they do help me -- garage lights, for example.)

I appreciate the thought. But been there, tried it, and am still looking to make mods for her. What I discussed is exactly what I'd like to do -- have the volume control initiate a 10-minute enable for the audio, returning to a mute state afterwards without powering down the system. At least, that's what's needed in _some_ cases.

I have two ideas I plan to try out in a few weeks when I get some off-time to try them. Looking for more.

Thanks, Jon

Reply to
Jon Kirwan

From recent discussion in c.a.e:

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This thing can be turned into a wearable monitor.

VLV

Reply to
Vladimir Vassilevsky

On a sunny day (Fri, 11 Dec 2009 17:33:16 -0800) it happened Jon Kirwan wrote in :

Are you not approaching this from the wrong perspective?

Long ago I had something to do with seizure detecting equipment in some hospital. Some guy had designed a system that monitored the beds by having a contact that would make if there was strong vibration, and the contact sequence was monitored for a specific pattern to give an alarm, and start a video tape recorder. The staff could then react on the alarm, and later study the recordings. So I wonder if you could make her wear some gadget with a some vibration sensor that would send a wireless alarm, if needed with GPS position, to you or some help agency? That would be more rest for you, and more reliable. The trick IIRC was in the detection of the sequence. But in that system I worked on there was no micro, in those days, a modern small micro like a PIC could easily be programmed to detect specific sequences, say spectra. Maybe wear it on the arm, or on a belt?

Reply to
Jan Panteltje

...

...

How about:

1) proximity switch that detects the hand or finger near the control. (thin foil sense electrodes under adhesive film around the control?) 2) capacitive displacement sensor where you could add a vane to the pot. shaft inside the box that detected change of position. (same circuit as #1?) 3) button press detection, either sensing levels on the existing button or a touch switch overlay, or a second switch inside the case. 4) for units with a remote control: an IR receiver, or tap on the existing IR receiver module, or detecting the flicker on the visual feedback LED that most stuff seems to have, these days.

Mark Zenier snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

Reply to
Mark Zenier

By the time you hear the sounds, it might be too late to avoid broken arms. But at least to have early treatments.

ospital.

t that would

d for a specific

sensor that would send a wireless alarm,

n small micro like a PIC could

If you can get help with precision military GPS technology, you can perhaps detect unusual positions such as laying on the ground.

Reply to
linnix

I certainly could be. :)

hospital.

would

a specific

My wife and I have discussed this. In fact, as late as this morning. More on that in a second...

We were, in fact, talking about having her wear some kind of wrist bracelet. However, there are complications. One of them is her own willingness. I cannot express to you just how difficult it has been to get her to do so much as wear underpants. She is highly sensitive to 'touch' on her skin. We fought for years and years, almost minute by minute in battles with her, over things like this. Even today, getting her to keep something on will be _very_ difficult.

I'm not saying 'impossible', as this is something we did talk about today and could consider as an option. But it probably won't be easy to design for her sensitivities, let alone it's technical function.

One last thing, transmitters use lots of power. Even receivers do (though that can be mitigated by powering up and powering down between selected intervals.) A solution that would work (as you will see why in my next comment) is to avoid a transmitter of any kind and instead use a piezo tweeter that we'd hear. However, there may be false positives and these will 'drive her nuts.' I need to work on that aspect so that what sound is made is okay with her, but noticeable to us. I can do that.

That's not needed. We are here with her, 24/7. It's what we do. She is never more than 50' from one of us. Not ever more, for any time.

Perhaps. It would not abate the noise level, which has other (less important) consequences. But you are right that it is worth considering closely.

However, there is another consideration. Detection. I've watched many times while she stands upright, suddenly goes completely stiff like a board (no noticeable vibration, body-wise, but a gasp of sound that escapes for a moment from her because of the sudden lung pressure change) for perhaps 10 seconds or so and during which time she loses balance and simply falls over onto whatever is there. (We catch her, if we are close enough to get there, of course.) Detection is going to be difficult. I don't mind some false positives, though. We already deal with plenty of those just from our own constant worry.

Yes.

I could, over time, develop data on the variety of her responses and select out portions of that and use cross-correlation for detection, I suppose. There are other approaches, too. But I would have to do a lot of data gathering to detemine what works best for her. It's possible that in the process I may develop something more generally useful. That would be a side benefit.

Lots of possibilities. Thanks for thinking with me about this. Much appreciated.

Jon

Reply to
Jon Kirwan

This is always an issue with us. We move quite quickly when we get a sound we recognize. Many times we are able to catch her before she reaches the ground, as she stiffens and it takes a few seconds for her to topple if she is standing at the time. (She doesn't fall like a rag doll, though she might be in a precarious orientation that can fall as quickly.) Sometimes, it happens while she is laying down -- some of which we believe is because she can sense something wrong beforehand -- though we cannot ask her as she has no language for that.

What's important here is that we hear _better_ so that some of those occasions we don't hear right away are heard earlier and that gives us a chance to mitigate effects. For example, although we have removed the possibility now there was one time where she trapped an electric space heater between her legs during a seizure. It did shut off as it should (tip sensor), but it was still quite hot on parts of the surface. And as you can imagine, this led to inner thigh burns. Getting there quickly meant less damage than otherwise.

So very definitely every single second of improved response time counts. It can mean the difference between life or death, ultimately.

Jon

Reply to
Jon Kirwan

Just a wild thought... Video surveillance with motion detection.

--
Best Regards:
                     Baron.
Reply to
Baron

When I first read your response here, my mind immediately went to the TI watch mentioned in CAE. I first read about it in the Yahoo group for the MSP430, of course. And I looked closely at the possibility at the time. I'm still considering it. However, I have spent quite some time working with her to wear a watch of any kind, to no avail. She is fascinated by them and loves to take my watch off and put it on. She likes the details of doing that. Sometimes, if she notices I don't have it on she will ask me, "Watch?" But I've been unable to get her to wear one for more than perhaps a few seconds. And I've tried. Hard.

So, tempting as it is and as much as I appreciate your noticing this and bringing it to my attention (it was a _smart_ thought), I'm still struggling about the her response to it.

That said, I had already ordered the US band version on the possibility. I'll need to do data gathering first, then consider what analysis of it shows me. I am still not sure what data will be available. As I mentioned elsewhere, she stiffens and doesn't shake much, to start. By the time she is shuddering, we are almost always already there. That doesn't mean we can't use the shuddering, because it will help ensure closer to 100% that we notice the event. But I'd like to catch things even earlier.

One of the reasons I'm thinking more towards the mute, is in fact because my wife and I are so good, already, at detecting the early gasp. One of us never leaves her, by much distance. We run around turning things down, when she isn't using the devices. That is, when we think of it. Which isn't something we are always conscious of, since we've learned to tune out the sound and have to fight that tendency. However, she would quickly get used to an auto-mute and would learn to _accept_ it's rules and the effect would be that our own failures to be constantly conscious and attentive to the equipment would be covered better, leaving our own fine-tuned detection skills to operate better as a practical matter.

I suspect this will be an ongoing process of adaptation for most of the rest of our lives. Piecemeal technical solutions will address only some of that. But even one partial-crutch is appreciated.

Jon

Reply to
Jon Kirwan

It's not a wild thought, at all! Been there, done that. We live the problem and have tried that, so it's a great suggestion. (We have baby monitors running all the time, too.)

We just cannot sit around glued to a screen. We must keep house, work on outside projects (we live on a farm with chickens, guinea hens, peafowl, and acres of gardens and orchards), clear out downed trees, make wood boards and chop and stack wood, repair the driveway or broken water pipes, etc. I'm building a new home for my son in one corner, by hand without help except for his -- which was a very serious problem when pouring concrete.)

Besides, motion by itself isn't 'detection' of an event. She moves around freely, all the time.

And I think the video processing required to 'detect' an event from the images would likely be beyond my skill set to imagine. I've done spatial filtering optics and vector light propagation through optical systems and beam-forming for underwater detection systems (with propagation of sound across thermal layers), so I am comfortable with mathematical techniques. I just lack the imaginative ideas needed to see my way clear to something there. If someone else knows enough to suggest some details, I might give it a heave or two. But I'd need to 'understand' it.

Thanks, Jon

Reply to
Jon Kirwan

Thankyou for not rejecting my suggestion.

I wouldn't dream of suggesting that you spent your time in front of a monitor screen.

There are systems which are capable of detecting changes in an image and following those changes around. Normally you would be looking for movement there. If instead you looked for lack of movement, that could trigger an alarm. I know that PIR detectors can detect the heat from a body continuously. So a IR camera might do the job.

--
Best Regards:
                     Baron.
Reply to
Baron

Let me see if I understand the functional requirements:

1) Every X minutes, mute the device 2) Un-mute it when the volume control is fiddled

Is that exactly what you want in terms of function, ignoring the technical requirements (no holes, power supply considerations, the muting device or circuit needs to work with several different pieces of equipment, whatever)?

Ed

Reply to
ehsjr

(And I seem to recall some short discussion here about a new kind of sensor along those lines which inherently sets up potential differences when there are changes in the flux across the surface.)

Detection remains a problem here. Often, she lies down and doesn't move -- either awake or asleep. Too many false positives and we'd learn to ignore it.

Jon

Reply to
Jon Kirwan

Yes. That pretty much nails what I'd like to try out, right now.

As should be abundantly clear, we are hacking out new territory and always experimenting to improve the quality of our results with her. So once we field something, we may discover new effects to worry about.

It's kind of like the "theory of pendulums." You can start out very neatly describing the motion, constraining the swing such that sin theta = theta to a reasonable approximation to eliminate confounding terms, and yield the well known pendulum law. However, when you start actually _building_ pendulums and when you improve your measurement precision of the timing over time, you find the theory doesn't take into account the diameter of the holes that rock on the pins you build, relative to each other, which can affect the predictions by 2 or 3 percent or more -- which cannot be explained by timing measurement errors alone. So you search out this new effect, discover it, and then want to deal with it, too.

I expect that once we get this working, what is currently obfuscated by the magnitude of the current problem will be stripped away to view and we'll probably have some new thoughts to add, then. For now, I can't see any of that so this is exactly what I'm looking for.

It goes in incremental steps. Like life.

Jon

Reply to
Jon Kirwan

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