Timeline for Do ‘wiperless’ potentiometers exist?
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| Jun 11, 2020 at 15:10 | history | edited | CommunityBot |
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| Mar 9, 2015 at 19:34 | comment | added | leftaroundabout | Terrific answer, though I'm not sure rolling contacts are as bad an idea as you say. A mechanical mouse's rollers have to work under very adverse conditions, namely, they're directly fed the grime from the surface you're moving the mouse on. In a potentiometer, this sticky kind of dirt shouldn't ever enter in the first place, only much lighter dust. And a rolling design might be easier to make dust-proof than a sliding one: if the rolling action is actually just a couple of degrees of large-radius circle segments, you could vacuum-seal this and actuate it with a screw moving only a few mm. | |
| Mar 9, 2015 at 17:58 | comment | added | James Haigh | Wow, thank you for this incredibly comprehensive answer! I couldn't keep-up reading your large expansion of edits or everyone's comments yesterday. Your answer has a lot of useful information. Particularly the noncontact potentiometers are interesting, because they can be modelled by an ideal potentiometer with a capacitor connected to the middle pin, right? I'd never route audio through a potentiometer in my own designs (I'd use a circuit fragment similar to the one that you describe), but I'm asking about the individual component rather than how you'd implement a volume control knob or such. | |
| Mar 9, 2015 at 13:31 | comment | added | Kuba hasn't forgotten Monica | @pjc50 I'd say that any EE undergrad should be building such things (not necessarily from any particular list, of course), like crazy - it's a lot of fun, and it's amazing how many ways any particular problem can be cracked. It's also amazing how useful the modern semiconductors are. You can get a lot done for ten bucks :) | |
| Mar 9, 2015 at 13:16 | comment | added | pjc50 | Sorry, I'd missed that. It's a very impressive list, the sort of thing that should be issued as further reading to EE undergraduates! | |
| Mar 9, 2015 at 12:47 | comment | added | Kuba hasn't forgotten Monica | @pjc50 I mentioned just such a device in my bucket list. I didn't think such a device should be called an encoder. When you have coding, you - by definition - transform discrete information. In most cases, the linearity of the detector is vastly better than that of the process modulating the light intensity. Even a 741 hooked up to a phototransistor or a photodiode is much better than the cheap V-slit feeding it would ever be. | |
| Mar 9, 2015 at 12:40 | comment | added | pjc50 | You can build a fully continuous optical encoder by gradually occluding a light or changing its incident angle. It's just that then you're hostage to the linearity of your detector. | |
| Mar 8, 2015 at 22:37 | comment | added | Kuba hasn't forgotten Monica | @2012rcampion You can certainly supply phantom power to the guitar, if you can live with <10mA of current available from most supplies. The less you use, the better. If you want to use a stereo cable and a custom supply breakout box, it's easy enough to feed as much power as you wish. | |
| Mar 8, 2015 at 22:20 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 22:10 | comment | added | 2012rcampion | Unfortunately a pot is really your only option on the guitar itself since it's unpowered. Even effects pedals (at least the cheap ones I've dismantled) use the pots directly in an opamp buffer. I'll have to look into the photoresistor design. | |
| Mar 8, 2015 at 22:03 | comment | added | Kuba hasn't forgotten Monica | @2012rcampion Fankly said, I would not apply a pot directly to the audio signal even on a guitar. In fact, I would never ever apply it directly to an audio signal period. It never is a durable solution, and replacing crackly pots is not my favorite pastime. Probably the simplest low-distortion controlled resistance is a photoresistor - it would be a way better element for volume control than a pot. | |
| Mar 8, 2015 at 22:00 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 22:00 | comment | added | 2012rcampion | You're right, I wouldn't use an encoder to replace a pot in any analog circuit (say, the volume pot on a guitar for example). I'd use it if you're digitizing the output anyway (e.g. to read into a uc or to control the output gain on a dac). | |
| Mar 8, 2015 at 21:54 | comment | added | Kuba hasn't forgotten Monica | @2012rcampion The major problem with encoders is that they offer a discrete output. If one cares, as some people do, about a truly step-less output, that's only time-discrete if at all, all those other methods can work quite well. Everything depends on the degree of overboardiness you wish the project to be. For a vanity project, the funkier the better :) | |
| Mar 8, 2015 at 21:49 | comment | added | 2012rcampion | If you can handle the additional complexity, a rotary optical encoder is probably your best bet. They're used extensively in the space industry because they're low power, reliable, and don't wear out. (I'm working on a payload that's using a potentiometer to save cost, but let me tell you it's not worth it.) | |
| Mar 8, 2015 at 21:37 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 21:11 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 21:00 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 20:51 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 20:35 | history | edited | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |
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| Mar 8, 2015 at 20:26 | history | answered | Kuba hasn't forgotten Monica | CC BY-SA 3.0 |