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Afraid the only thing I got is this dutch stuff which I don't understand. I can tell it mentions what equipment is needed and to use a frequency generator. Don't got one however.   
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Feb 21, 2022 11:37
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babyeatingpsychopath posted:There's a newer/different version that I can't seem to find right now that's all about transistor mixers and has the diagram of what your signal should look like at every stage when you probe it with your o-scope. From the 70s, so analog o-scopes and early transistors. I'll see if I can dig up the title. This book sounds interesting by the way, would love to know the title.
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Feb 21, 2022 14:10
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I was going through close up photos I've taken of the components (to help me ID caps) since I am at that stage where I tihnk it's worth replacing all the electrolytics. And possibly the diodes and transistors part of the AM circuit too. Anyway to the right, that looks like a crack on the component, not quite sure what it is yet, but it looks suspicious...  e: Found it on the schematics, supposed to be a 100N capacitor. Add those to the list I guess. Maybe I should replace all these colored caps too. What are they, polyester film capacitors? e2: I managed to get a signal, several in fact, by touching a wire to one of the leads from the internal antenna. The connection to the board is fine though. So I then touched the windings and squeezed them and the signal appeared again this time without holding a wire to them. So I believe now the problem all along was that the internal AM antenna was broken. What I don't understand is why the radio did not immediately work when I plugged in the external antenna then... There's also still a weird behaviour where the signal strength seems to flip to max and the radio stops receiving the proper signal and instead picks up something else. His Divine Shadow fucked around with this message at 18:59 on Feb 22, 2022 |
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Feb 22, 2022 11:54
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Anybody here familiar with these: https://www.digikey.com/en/products/detail/spectra-symbol/SP-L-0100-103-3-RH/2175419 Do they just work as a pot? Maybe I'm missing something but that appears to be what they do. 
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Feb 22, 2022 21:27
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petit choux posted:Anybody here familiar with these: Check out the datasheet. That's exactly what they do, but you need some kind of spring loaded pusher thingy to exert 1-3 newtons of force on it. That's cool, I wasn't aware of these. edit: Seriously check out the datasheet, love the graphics, and it also goes on to say that you can just use your finger or whatever. They're kinda pricey though. If you can roll your own with some kind of resistive flexible medium, maybe a 3d printed spacer, and a PCB, that might be cheaper. Still really cool though if you have the money and it fits your requirements. If the entire thing is flexible, that and the adhesive backing makes it really potentially cool for wearable electronics interfaces. Effective-Disorder fucked around with this message at 23:27 on Feb 22, 2022 |
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Feb 22, 2022 23:16
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Effective-Disorder posted:Check out the datasheet. That's exactly what they do, but you need some kind of spring loaded pusher thingy to exert 1-3 newtons of force on it. That's cool, I wasn't aware of these. I think maybe I'll just order one or two just to play with at least for starters. Pretty fricking cool!
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Feb 22, 2022 23:37
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It reminds me of the fingerboard from the Otamatone. Clearly this needs to become some kind of musical instrument.
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Feb 22, 2022 23:46
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Stack Machine posted:It reminds me of the fingerboard from the Otamatone. Clearly this needs to become some kind of musical instrument. Agreed very excited to try it
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Feb 23, 2022 00:32
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I did a thing, a teensy based midi controller. I'm not super proud of it but I've never completed a project like this so you know.. sorta happy. It was a good learning experience, I just kinda guessed with wiring and it works but I'd like to do it better in the future. Acrylic was a mistake too for something I'm going to be touching constantly. But it was cheap and getting stuff laser cut was also a new process for me. At some point I'd like to do a full enclosure for it.  See if you can spot the big mistake! I forgot to figure out a place to mount the pcb so I hot glued some risers to the base
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Feb 23, 2022 01:48
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petit choux posted:Anybody here familiar with these: Beaten, but I've used those before and yes, the output is a variable resistance. When you press on it close to the contacts it gives you a low resistance, and when you press on it down near the bottom it gives a high one. You do have to apply a little bit of pressure -- it's resistive, not capacitive -- and if you put two fingers on it at different points you will get the lower of the two resistances. Also it isn't strictly like a potentiometer, which is a three-terminal device. It's more like a photocell, thermistor, or other variable resistor. To read it with a microcontroller you'll need to build a voltage divider using a second resistor of appropriate value. Effective-Disorder posted:. If the entire thing is flexible, It is
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Feb 23, 2022 02:28
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I finally sourced the original 1992 schematics for a SCSI interface board for my old S950 sampler. They were unobtainium so I had to scour the net until I actually found someone selling a physical copy. Anywhoo, part of me thinks this would be a pretty interesting project to see if I can learn anything fun by literally just trying to clone the PCB in kicad or something.  I’m not certain I’d be comfortable actually building it and risking accidentally frying my vintage sampler in the process, but who knows. I think SCSI ICs of that era are going to be impossible to find anyway, so I’d have to figure out pin or protocol compat parts and adjust layout to suit. I know folks have made (expensive) aftermarket clones with newer ICs so it’s probably just a matter of finding a protocol compatible part, and I think just digging in a little to see what chips they used would confirm. Still way above my skill level to figure out how to adjust the PCB to match so I’d probably have to come back here for advice if I ever get that brave. Anyway, I think maybe just setting a goal of replicating this board and getting a fancy black board printed just to have would be fun so I guess I might have a bunch of kicad questions in the near future. E: here’s the rest just for funsies:    
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Feb 23, 2022 03:00
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I have an idea for a very stupid joke project and want to know if I'm on the right track: I plan to invent the 'electronic cigarette', a standard tobacco cigarette with a small LCD display telling you how much % of the cigarette is left obviously I'd like to, in actuality, make it a non-disposable device that goes around/through a ciggie- my first intuition is to run a thick wire (like paperclip-gauge) through the cig from filter to end, read the resistance of the wire when N% of it is exposed to open air (vs encased in tobacco), and use those values in arduino code to approximate a "% remaining" figure. is this the right approach to a wrong idea? if I test this out by rolling up mint or catnip (I don't smoke, but some friends do, so I have test subjects), is it likely to significantly alter the resistance of the wire vs being packed in tobacco? e: i guess i could also test it with [FULLY LEGAL CBD-BEARING PLANT MATERIAL] Peanut Butler fucked around with this message at 03:07 on Feb 23, 2022 |
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Feb 23, 2022 03:05
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petit choux posted:I think maybe I'll just order one or two just to play with at least for starters. Just hoping that you'd better post whatever comes of this. I don't care what it is, but do something weird and/or cool, ok?
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Feb 23, 2022 03:17
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Peanut Butler posted:I have an idea for a very stupid joke project and want to know if I'm on the right track: Don't they already do something like this in Japan?  edit: I seriously don't know how this is that different from just smoking a drat cig. Even if you have a feedback temperature control system to prevent actual combustion, this is obviously a desperate attempt of Japan Tobacco to maintain their nut wrench hold on wage slave nicotine addicts. I used to smoke 1mg cigs in Japan for a month at a time before I got tired of it, and this is just pathetic. Their idea, not yours, although it would really just end up in the same category if you think about it too long. Don't smoke cigs if you don't smoke already, poo poo's bad for you. Also don't invent awful technology that will just be used to further subjugate us enthralled nicotine addicts with more technology as a "smokescreen" lol. Effective-Disorder fucked around with this message at 03:24 on Feb 23, 2022 |
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Feb 23, 2022 03:19
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that's an herb vaporizer, like a Pax or the venerable Volcano my idea is much dumber, thank you very much
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Feb 23, 2022 03:24
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Peanut Butler posted:that's an herb vaporizer, like a Pax or the venerable Volcano Look closer at the photo, the filter says 'Marlb', it's awful tech. Don't do it. It's all bad. You cannot be dumber than that photo, I assure you. Just don't try to do it. You are better than this.
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Feb 23, 2022 03:25
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Peanut Butler posted:that's an herb vaporizer, like a Pax or the venerable Volcano Also I did have a period several years ago where I was actively developing a solid state laser bong, nothing good came of it, aside from now owning some blue diode lasers and the appropriate safety gear to handle lasers. I learned about diode lasers, but nothing else good came of it.
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Feb 23, 2022 03:29
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Effective-Disorder posted:Look closer at the photo, the filter says 'Marlb', it's awful tech. Don't do it. It's all bad. You cannot be dumber than that photo, I assure you. Just don't try to do it. You are better than this. yeah it's a dry herb vape with a short specially-made marlboro cig stuck inside  a difference between the World's First Electronic Cigarette (my device) and both the iqos and the laser bong is that the latter two have use cases: smoking without producing secondhand smoke, and lighting a bong I just think it would be funny to make an electronic device that uselessly tells you that your cigarette (or whatever you're smoking, come to think) is almost gone
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Feb 23, 2022 03:36
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Peanut Butler posted:yeah it's a dry herb vape with a short specially-made marlboro cig stuck inside Print a ladder shaped resistive element in the wrapper with inkjets and embed the microcontroller in the filter, but you know this already. OLEDs in the filter show you how much you've smoked. Hell, make a thermocouple layer using nanotech inside the wrapper and you can power the entire drat thing at the same time. Thermal battery indeed. As for secondhand smoke, nobody cared, we all just huddled by the smokeless ashtray, which lionizes the dad from Gremlins. Anyway I salute your mindless attempts at creating something even more absurd than the iQuos. I might even use it, and if you pay me enough to offset my lung cancer bills, I'll sell it. Effective-Disorder fucked around with this message at 03:49 on Feb 23, 2022 |
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Feb 23, 2022 03:42
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Sagebrush posted:Beaten, but I've used those before and yes, the output is a variable resistance. When you press on it close to the contacts it gives you a low resistance, and when you press on it down near the bottom it gives a high one. You do have to apply a little bit of pressure -- it's resistive, not capacitive -- and if you put two fingers on it at different points you will get the lower of the two resistances. So it's not actually a drop-in replacement, thank you. Though this voltage divider you mention does not sound complicated. If you have any further wisdom in that regard or any other, I'd love to hear it.
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Feb 23, 2022 05:22
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Does anyone have an idea on the best way to make a low-voltage disconnect without using a relay and without a voltage drop from the "monitor" (e.g., zener into a transistor base)? I have a 12V source and I want the entire circuit to lose power when the voltage drops below 10.0, and then not turn back on until the voltage reaches 11 volts. I think this functionally accomplishes what I'm looking at, but doesn't have the "turns back on at V+X" (and I didn't calculate the values, just a qualitative schematic). Is there a better option? 
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Feb 23, 2022 06:45
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petit choux posted:So it's not actually a drop-in replacement, thank you. Though this voltage divider you mention does not sound complicated. If you have any further wisdom in that regard or any other, I'd love to hear it. A voltage divider is very simple -- just two resistors in series with a voltage across them. By Kirchoff's laws, the voltage in between the two will be some factor of the voltage across both according to the ratio of the resistances. For a trivial example, if you have two identical resistors in series and you put 5v across them, each one will drop half the voltage, and the voltage measured in the middle relative to the circuit ground will be 2.5v.  If one resistor is larger than the other, the voltage will shift towards one end or the other. E.g. if the resistor that's closer to the positive side is much smaller, the voltage in the middle will be higher. Here's some math about it https://www.allaboutcircuits.com/textbook/direct-current/chpt-6/voltage-divider-circuits/ A potentiometer is a variable voltage divider in a box. As you turn the knob pictured below clockwise, the resistance between GND and the center pin goes up (because the resistive trace length between them gets longer) and the resistance between the center pin and Vcc goes down. This lets you smoothly divide the voltage to anything between Vcc and 0, which you measure between the center pin and ground. Microcontrollers can read this varying voltage and that's how the input works.  Potentiometers can also be used in analog circuits, sometimes only using two pins, but I only feel like talking about digital ones right now.  A variable resistor like that softpot, or a photocell or a thermistor, does not have this special potentiometer characteristic. All of those devices literally just behave like resistors that change their value with some input. In order to get a microcontroller-friendly variable voltage out, you need to build the rest of the voltage divider. All this means is putting a second fixed resistor in line with the variable one:  As your variable resistor changes, the ratio between it and the fixed one also changes, and so does the output voltage. Easy. You will never get the full 0v to Vcc range with this design, because one leg of the circuit can never go to zero ohms, but if you pick the right value you can still get a useful output range. I like to make the fixed resistor about 1/5 of the maximum value of the variable one. As for whether this can be a drop-in replacement for a potentiometer -- that totally depends on how the potentiometer is being used. If your system s reading the center voltage, then it will absolutely work, but you might not get the full range of the original pot. If it's doing some analog stuff and directly reading two legs of the potentiometer as a resistor, then you might be able to get a perfect result just plugging your variable resistor in -- or you might be completely out of luck if the variable resistor doesn't have the same range as the original pot. Sagebrush fucked around with this message at 06:52 on Feb 23, 2022 |
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Feb 23, 2022 06:49
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PRADA SLUT posted:Does anyone have an idea on the best way to make a low-voltage disconnect without using a relay and without a voltage drop from the "monitor" (e.g., zener into a transistor base)? The term you're looking for is hysteresis. There's a good guide here, from skimming: https://www.homemade-circuits.com/opamp-hysteresis-explained/
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Feb 23, 2022 06:58
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Sagebrush posted:Also it isn't strictly like a potentiometer, which is a three-terminal device. It's more like a photocell, thermistor, or other variable resistor. To read it with a microcontroller you'll need to build a voltage divider using a second resistor of appropriate value. The one linked does work as a pot, though. From the datasheet:  So you can drop it anywhere a 10k pot would go, as long as the circuit can handle having the wiper disconnected when nobody's pressing on it.
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Feb 23, 2022 15:03
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Stack Machine posted:The one linked does work as a pot, though. From the datasheet: Aha! I was just looking at the datasheet myself.
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Feb 23, 2022 15:56
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These are the basic FSR circuit blocks:  Somewhere I've got a good PDF discussing the best ways to extract a clean gate pulse, and then onward to sample'n'hold the FSR's value upon releasing your finger (so the pitch of whatever you're controlling doesn't ping off to the rails if it has a release envelope). However, I'm not finding that PDF in my normal circuitry document places. 
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Feb 23, 2022 16:04
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Stack Machine posted:The one linked does work as a pot, though. From the datasheet: Yeah, I'm unclear on that, it seems like a serious limit on what can use it. But I think I have an Arduino device that uses pots where you'd usually use some kind of switches or something, I'm thinking this might be right for it. I guess there's code that maps amount of resistance to certain instructions and a lot more, I'm kinda hoping this might work that way. ED: Probably a good idea to ask the person who made the device at this point. petit choux fucked around with this message at 17:26 on Feb 23, 2022 |
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Feb 23, 2022 17:24
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ante posted:The term you're looking for is hysteresis. There's a good guide here, from skimming: This also goes by the name Schmitt Trigger if you (PRADA SLUT) want another term to search on.
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Feb 23, 2022 23:59
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I'm looking at a 3-cell NiMH pack that has a 3-wire connector. What is the third wire for? Given that it's a 3-cell pack it doesn't seem like a balancing connector (you'd need a 4th wire to hit all three cells). I guess it could be a 1-wire connector to a controller board but you don't normally see that kind of smarts on a NiMH pack, and I don't see one in there. I'm a little stumped. It's for a Symbol DS6878 cordless barcode scanner if that helps.   Maybe they're tapping off 1.2v or 2.4v to provide a different logic level, despite the fact that would unbalance the pack a little bit? If you didn't pull too much, and you individually peaked that cell when on the charger, it would probably work. Paul MaudDib fucked around with this message at 21:40 on Feb 25, 2022 |
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Feb 25, 2022 21:37
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It's probably a thermistor connected to the ground wire. AFAIK NiMh fast chargers have to sense the battery temperature rise during charging to determine when to change modes or something like that, so it's common to include one for that purpose (not just for safety).
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Feb 25, 2022 22:31
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So I got the replacemetn op amp for the electronic load from before. It seems like it also blew away most of one pad, but I managed to solder it on to something. It still doesn't work. and a crappy diagram  Since the microcontroller seems to work fine, I'm mostly looking at the op amp and transistor part. For a 5V source voltage (from a power bank), In+ is 3-600mV depending on the current dials. V- and In- are GND. V+ is getting about 7V and Vout 5.7-5.2 depending on the pots. I've no experience with Darlington transistors like this TIP122, but the Base and Collecotor seem to be both shorted to the input source (5V in this case again). Is there any legit reason it would appear this way? Would it make sense to test it outside the circuit? LIke an idiot I didn't think to get a spare one as well 
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Feb 26, 2022 18:21
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If the base and collector are at 5V and the emitter is at 0V and it's not smoking hot now, it was probably smoking hot at some point in the past. The emitter should be 1-to-2V below the base on a darlington like that.
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Feb 26, 2022 18:54
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Thanks! It's not getting hot right now but it doesn't mean it wasn't glowing when everything blew up  I can't find my wick but i'll try to replace it next week and hopefully that'll do it.
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Feb 26, 2022 23:55
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Yep. I wouldn't expect it to be operating undamaged with 5V from base-to-emitter. If I blast 60mA into the base of one I see 1.5V from base to emitter, and that's already more current than your circuit could provide with that 600 ohms in series with the base. 5V is an alarming voltage to see there, considering that the rule of thumb for silicon diodes is 60mV per 10x increase in current. This is basically 2 diodes in series, so each 120mV would correspond to a 10x increase in current. What really happens is internal resistances eventually start to dominate so you're looking at a few amps instead of a few sextillion or whatever at higher voltages, but that still makes 5V scary.
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Feb 27, 2022 06:33
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Does anybody have any recommendations for capacitve sensing of large objects? I've got a project where I want to be able to sense if somebody touches a large metal object, something like a cast bronze statue. I've done capacitive sensing before, and generally have hit limitations on the size of thing I can sense. I'm using things like adafruit's cap sensor breakouts, or sometimes little sensors from Omron or others. They don't do well once you get to big chunky things - the natural capacitance of that much metal tends to become a problem, and the static of the local environment becomes an issue too. Worst case, I could fall back on a tight-beam motion sensor, but I figure with the number of lamps out there that have touch sensing, there must be a way to do it for big things. There's a part of me that is tempted to just use the dang lamp sensor, but I'd rather not have to use a 120V input relay to handle getting it to talk to a microcontroller.
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Mar 2, 2022 20:50
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Fanged Lawn Wormy posted:Does anybody have any recommendations for capacitve sensing of large objects? I don't think a motion sensor would work because the effect you're going for would trigger before they actually touch it, then you have people realizing that and waving their hands around trying to figure out where the motion sensor is, and focusing on that instead of the art/experience you're trying to create. I have no idea how capacitive touch sensors work. Tiny current through a capacitive medium?
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Mar 2, 2022 21:07
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Yeah, basically. A tiny charge is put in and drained. The time it takes to drain is what tells you if something is touching Agreed its not exactly the same, but using a tight enough beam/snoot on a PIR, You can get a pretty close to similar feel if you arrange it just so, but that is circumstantial to what Im doing here.
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Mar 2, 2022 21:17
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High voltage and a microphone would detect if someone touched it
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Mar 2, 2022 22:23
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Lazy solution: Put up a metal railing all around the statue, just far enough away that somebody would have to grab the railing to lean in & touch the statue. The voltage differential between the statue and the railing are left to your discretion. Or, when you think about it, the leyden jar is the original capacitive touch sensor...
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Mar 2, 2022 22:48
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Fanged Lawn Wormy posted:Yeah, basically. A tiny charge is put in and drained. The time it takes to drain is what tells you if something is touching Capacitive level sensor for industrial control. They're used in hazmat/explosive/etc spaces where other methods aren't compatible. They're eye-wateringly expensive, but will absolutely do what you need. These are designed to sense the liquid level of a specific substance with a probe that's partially submerged in the liquid. The amplifier can be a general level-sensing "xxx liters" or a limit switch (high limit, low limit, etc). You'd get a capacitive limit switch amp and wire it up so that when something touches the object, the amp outputs its signal. There will be some calibration and stuff involved, but these are very widely applicable industrial units and have a very wide range. babyeatingpsychopath fucked around with this message at 00:06 on Mar 3, 2022 |
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Mar 3, 2022 00:01
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