retrofitting an auto-mute volume control?
in [Design]
|
Prev: Triac controller IC
Next: RTD linearization
From: JosephKK on 19 Dec 2009 15:05 On Sat, 12 Dec 2009 18:01:38 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Sat, 12 Dec 2009 19:41:58 -0600, "Tim Williams" ><tmoranwms(a)charter.net> wrote: > >>"Jon Kirwan" <jonk(a)infinitefactors.org> wrote in message >>news:ne48i5d7bffiq5c1cvt7nbbnrq3ljtlj53(a)4ax.com... >>> 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. >> >>Would it do to have a camera mounted fairly low, so that continuous motion >>only in the lower half of the image corresponds to a siezure? This also >>assumes she isn't constantly moving around when lying down, of course the >>magnitude of motion could be controlled too. > >Interesting questions. Some hours of each day, she just goes into her >room and lays down under a blanket and looks at the ceiling, laughs a >bit, rolls over, etc. Assume there is a camera mounted there. If she >has a seizure during her sleep (very rare, as it is almost always >within about 1.5 to 2 hours within waking up), that might work. But >she plays, too. Besides, her seizing when under a blanket is not the >kind of "wild flapping" that you see on TV, sometimes. It's as though >all of her muscles are tightened up -- she feels like a solid rock -- >and she is shaking somewhat. There is NO oxygen getting into her >blood, so she damages her brain if it lasts too long. It is very >tense, low-motion, and she can grind (destroy, even) her teeth in the >process or cut her tongue in half if her jaw clenches down hard >instead of up. Sometimes, the jaw opens and closes. Sometimes, it is >stuck open or stuck closed. Sometimes, that changes during the >seizure. But by and large, not a lot of motion. Just a sudden high >tightness tensing of muscles and fairly low-intensity motions that >last for between one minute and as much as four. > >Which reminds me... a pulse-ox might be appropriate for detection >after the fact. Oxygenation levels should drop precipitously. And >these are dirt cheap, nowadays, and not hard to develop either. Of >course, it doesn't solve the detection problem until after it is way >too late. But it would make sure we know close to 100% of the time >when one happens. And that has value, too. > >We do have, sometimes, some indications 10 or 20 minutes early. A >kind of spasmatic jerk in her hands and shoulders that isn't visibly >noticeable, but if you are holding her you can feel them. They are an >indication that we are within an hour or so and that can allow is to >dose her before it happens or to at least hover and be there at the >right time. > >My instincts tell me to hold off of using video processing, for now. >Difficult and expensive for all the needed coverage areas, processing >complexities, etc. I need to explore other solutions that I can 'see' >the other end of more readily, first. > >I'd also still like to try out an auto-mute or two, as well. Those >aren't more direct detection, but they enable our own ears and that's >also important. The twin approaches... auto-mute and direct detection >on her body are like playing this from two ends to the middle. On one >end, there is our own fine-tuned detection (ears and brain) where the >auto-mute helps us; and on the other end there is the direct detection >that provides an entirely different pathway for detection and can be >made to reach us by altering the 'signal' so that we definitely notice >it. > >Jon Myodetection might be possible. But it is a contact sensor and may be found unsuitable for that reason.
From: Jon Kirwan on 19 Dec 2009 15:50 On Sat, 19 Dec 2009 12:05:51 -0800, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >Myodetection might be possible. Any decent references? I've no idea what it is. Jon
From: JosephKK on 19 Dec 2009 15:51 On Sun, 13 Dec 2009 21:26:56 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Sun, 13 Dec 2009 22:47:39 -0500, ehsjr wrote: > >>Jon Kirwan wrote: >>><snip> >>>Do I get the gist so far? >> >>Yes, I think you understand it. The hysteresis does what you said, but >>it was more to make the trigger "window" a little wider, and make the >>switching crisp and definite. As far as moving the control in either >>direction, it is solvable as you said. Maybe use a second comparator >>set up to switch when the control moves in the other direction. As >>far as muting, use the comparator output(s) to reset the timer, and >>the timer output to switch the audio output line from the speaker(s) >>to a resistor or resistors and vice versa. >> >>Regarding the existing pot setup, it is often like this, >>where the signal comes from the preamp: >> Signal---[cap]---+ >> | >> P >> O<---- signal out to amplifier stage >> T >> | >> Gnd -------------+ > >Yes. I anticipate this _after_ the first stage's conditioning of the >input and well before the final power stage. > >Suppose that the 'signal out' you mention passes through yet another >cap before the next stage. If so, isn't this a problem for a DC path? > > || C1 > IN --------||-----, > || | > | > \ > Rx / || > \ <----||----- OUT > / || C2 > \ > | > | > --- > /// > >No DC current path, right? > >In any case, I just opened up my first victim. The pot has 7 points >of attachment into the PC board. Two of them are twist tabs for the >main mounting and are themselves grounded. Of the other five, they >are on 5-hole line tangent at the circumference. One of these is tied >to the same ground. But the other four 'go somewhere'. This sounds like a very standard audio (log) taper dual element stereo volume control. Most of the ones i have seen the physical elements are stacked along the axis of the shaft. > >Call the pins A, B, C, D, and E. Pin B is tied to the negative rail >(ground.) (Since there is a battery system, as well as AC, I can >verify that it is the most negative rail by using the most negative >side of the battery pack connection.) > >Here are the measurements against ground for two rotation positions: > > MIN VOL MAX VOL >--------------------------- >A 0.5 ohm 32.3k ohm >B --- --- >C 0.5 ohm 32.3k ohm >D 220 ohm 32.3k ohm >E 47.7k ohm 32.3k ohm > >Obviously, in-circuit and not desoldered. Interestingly, the >resistance between A and C goes from about 0 ohms to about 64.5k ohms >going from MIN to MAX volume, respectively. The resistance from C to >D goes from 220 ohms to 0 ohms going from MIN to MAX, respectively. Sounds like A and C are the "wipers" (output side). D and E are acting strange though. Take measurements at half rotation as well. It should help sort things > >That's enough to make this interesting. I need to think more closely >to be sure, but the pot appears to not be a single resistor track and >wiper, at first blush. > >I think I need to assume every other system will be just as messy. >Then, at least, the only way is down -- easier -- from there. > >>> Another issue is what mutes the output. If I actively mute, that act >>> itself will affect what those same nodes do for the comparator inputs >>> (filtered and unfiltered) since those nodes must be involved in the >>> muting, itself. That presents a possible problem. What I may like to >>> do is separate things so that I isolate the pot and 'copy' its value >>> to the prior nodes being controlled. Well, that gives me some thought >>> lines to move along. >> >>It should't affect the comparators if it occurs between the final >>amplifier and the speaker(s). > >I have a hard time imagining a pot right at the final stage, because >of the power (few watts, at least) involved. But you might be talking >about something else I said. > >>> Possible variations are discrete circuits, IC circuits, and a host of >>> topologies to ferret out and design around. Maybe the best way to >>> start is to just start. I'll open up one of the devices and see what >>> I see there. >> >>Good luck! > >Thanks. Looks like I'm going to need it. Blasted thing. > >Jon
From: Jon Kirwan on 19 Dec 2009 16:07 On Sat, 19 Dec 2009 12:11:24 -0800, JosephKK wrote: >On Sat, 12 Dec 2009 18:35:00 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: ><snip> >>Probably will need to do a 'shrink' on it, though. It's too big as it >>is. Much too big. She won't wear it for long. But I'm going to try >>it out, anyway. Still looking for auto-mute ideas, though. This >>isn't an either-or situation. > >It does not necessarily have to be a watch, it could be a necklace or >a tiara. She loves watches and takes mine off and puts it back on, a lot. I've even seen her 'try' to consider the idea of putting it on her own arm. But only for a moment. It took us many, many years just to get her to wear a t-shirt. As I think I already mentioned, she is very 'sensitive' to stuff that touches her. Most types of cloth are impossible and we have to carefully select textures and other factors. She still won't wear anything more than a long t-shirt and underpants, except in contained/controlled situations (such as driving in the car.) A necklace or tiara is not probably not happening. But every idea may be worth a try. Jon
From: JosephKK on 22 Dec 2009 01:58
On Sat, 19 Dec 2009 12:50:57 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Sat, 19 Dec 2009 12:05:51 -0800, >"JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>Myodetection might be possible. > >Any decent references? I've no idea what it is. > >Jon Basically it is the electric potentials that can be measured in correlation of muscle contraction. It is a well known interference for ElectroEncephalaGrams (EEG). Not much quality stuff on a quick Internet search: http://openprosthetics.org/myoelectric http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore..ieee.org%2Fiel5%2F10755%2F33900%2F01616206.pdf&authDecision=-203 |