I've been looking for this video! Every source of information seeking to explain how theremins work through sheer circuit theory fails to explain the point around the 2 minute mark. Surprisingly fantastic information I've been searching fro for years!
bravo, Bravo, BRAVO, B R A V O!!!! this is one of the best educational videos I've come across. Great explanation, great illustrations and given that it doesn't sound like English is your primary language, you knocked this video out of the park! I'm now your newest subscriber!
I must agree with all the comments. This is the best explanation and enhanced with demonstrative animation. Bravo! I look forward to seeing more of your posts. Thanks!
Thanks for posting this! I've been looking for this information for a long time. I'm still looking for a rigorous evaluation of the physics of coplanar capacitors. The illustrations help, but I'd like to be able to calculate the values based on given dimensions. I've found a few equations on the web that come somewhat close, but I'd really like to derive the equation myself. If anybody can give me a push in the right direction (not off of a cliff please) I'd appreciate it a bunch:-)
I used Azoteq IC to make the video. For single touch as an example, Azoteq offers IQS227. The theory I presented in the video works for all brands and implementations, whether it is the charge transfer or relaxation oscillation methods.
Very good explanation. We intended to use the IQS127D for one application where we currently use ATMEL. Only one doubt: In our application measured capacitance varies very smoothly, we are afraid that LTA functionality in AZOTEQ will adapt the sensitivity consequently missing then the detection.
Well done, I think it could be better by illustrating a simple kirchhoff current loop though. There is a board capacitance to earth ground, a human capacitance to earth ground, and a human capacitance to the board (touching). This forms the basic loop for current to flow. When the ground plane of the board is big, the board capacitance is big and then only the touch capacitance matters. When the ground plane is small, the board capacitance is small and then it attenuates the touch capacitance. But yeah, good work anyways.
I just saw your response about dealing with environmental drift and I'm a bit confused. My understanding was to keep the sensing electrode as close to the capacitive controller as possible to eliminate this type of parasitic influence. Do those IC's condition the sensing electrode in some way? Or is this just another way to keep the connection between sensing electrode and controller as short as possible? Either way, I've always set the triggering threshold myself at the controller.
The signal goes to the smaller plate. If the touch electrode is 1m^2, and the ground plane is smaller, a signal is produced when touching the ground plane (and NOT the electrode). If the ground plane is much bigger than the 1m^2, then the signal produced by touching the electrode will still be small, because the human body is well coupled to the electrode and ground plane to begin with, and moving the finger tip does not change in capacitor's geometry very much so the signal will still be very small.
I referred to the following materials for the classic "Method of Moment": 1) Harrington, R. F., Field Computation by Moment Methods, Macmillan, New York, 1968. 2) "The Method of Moments in Electromagnetics", MIT lecture notes, available on the internet (UA-cam don't let me put the link here) 3) "Numerical Solution for the Potential between Parallel Plates", Dr. David Jenn, nps.edu I had to extend the formulation to 3- or 4-body system to include a person in the simulation.
Fantastic job explaining this! May I also contact you with some follow-up questions? I have been working on a very ambitious capacitive sensing project for the past year.
Hi, I am currently working on a capacitive proximity sensor, and I would like to ask you some questions.I placed a large sensor (with only one plate) vertically 40cm above the ground, and then tried to approach the sensor with a larger copper plate to observe the capacitance value and how it changed.I used COMSOL software to conduct simulation tests, in which the sensor was set far away from the target object. My original idea was to take the capacitance change obtained as the parallel plate capacitance between the sensor and the object, and calculate the distance value from this value, but I found that the inverse distance value was wrong, that is to say, the formula of parallel plate capacitor is not applicable in this case.So I wonder if you know of a more suitable theoretical model of capacitance.
How big is the plate? When you said 40cm above the ground, is that the electrical ground plane or ground we step on? Using one large plate will not work, because the working principle is that 2 plates sense the external object. The smaller plate has a higher sensitivity and the bigger plate has a lower sensitivity. The large plate you intend to use as the electrode will work against your intention. I demonstrated this surprising and unintuitive result in my other video "teardown of miband3". The equivalent circuit is shown in ua-cam.com/video/ZHzaVzYEZbw/v-deo.html. The circuit is simple, but it does predict bigger plate having smaller sensitivity and visi versa. The parallel plate model is incomplete. I hope this helps.
@@SiliconSoup The plate's area is 24cm*24cm.The ground is ground we step on.My intend is to achieve a long proximity distance,e.g. 50cm.This purpose requires the use of larger plates.
@@伍攀-i1s Firstly, is your circuit battery powered or AC powered (through DC-adapter)? If you circuit is AC powered, inherently the circuit ground is connected to the earth of the electrical system, so you already have a big ground plane, so together with the 24cm X 24cm electrode, they can sense any big object coming in between them. The object will have to be same or bigger size to make significant change to the capacitance. However, if you have a 24cm x 24cm electrode, and a small circuit ground (if the circuit is battery powered), then the circuit will not work as intended. In fact you will find the sensitivity goes to the circuit ground, the small plate. So what you need to do is to enlarge the circuit ground to an area comparable or larger than 24cm x 24cm. Again, I like to emphasize that the capacitance between the single plate and the object need a good return path back to the circuit for the capacitance to be detected, that the good return path is formed by a much bigger ground plane coupling to the object. If you are dealing of long distance, the signal change can be small, so you need a sensitive capacitive sensing IC. Not all sensing IC have good SNR. I strongly recommend azoteq, because I experimented with it, and it is really good.
Hello. Thanks for the very good video. Can you recommend a book on that topic? You show some single figures and pages from different books in the video. By the way: Did you use a screen recording sodtware? Loos great! Best regards Manuel
I used Azoteq IQS222 and IQS127D for experiment. The sensitivity and stability are really good. The information about the eval-kits, including where to buy, is in their website.
In capacitive sensing, two electrodes (one is the circuit ground, the other is the touch electrode) are required to complete the sensing path, and the signal (delta C) has a bigger change at the smaller electrode. A big table will increase the signal level at other (smaller) electrodes, but the table itself will produce very weak signal and can't be use and the sensing electrode. /watch?v=ZHzaVzYEZbw in UA-cam.
In TTP223, if I make the ground pad smaller and the touch pad bigger, the sensitivity does not transfer to the ground pad. Why doesn't TTP223 follow that?
The ground is not just the pcb ground, but includes the battery ground or earth from the mains. If the battery is big, or the emulator has connection to PC ground,, or the DC adaptor is coupled to the earth, then the total ground is big, and the sensitivity is on the touch pad. The sensitivity is shifted to the touch pad when the device is powered by small batteries.
how to fake a touch using electronics like those shoulder buttons used to play mobile games like pubg and they press like 10x a second it uses capair capastive mapping technology what is that?
Hello! I'm 18 years old student in Korea. I researched on the principle of capacitive touch screen and the criteria of the substance that detects the input, several months ago. This is because it was interesting to know that touchscreen even works with materials such as water, salt, and polyethylene. I was able to find out some information about touchscreen, however, it is hard to find any more information about it on the Korean internetT.T If you have any facts about substance that enables capacitive touchscreen to work, please help me... I'll will wait for the reply!
The electrodes that detect the capacitance must be conductive, e.g. copper or ITO (Indium Tin Oxide). The gap between the electrode and the finger must be non-conductive, such as air, acrylic, glass, because electric field can pass through this media. Water, salt-water, aluminium cover are conductive and block the e-field and therefore should not sit in between the electrode and finger. Of course, a little bit of water on the cover will not block the e-field fully, so capacitive sensing is still possible, if the circuit is very sensitive.
@@SiliconSoup Thank you for your kind reply! I was overjoyed this morning. But I still have something that I can't understand. I think I had not been able to convey the meaning of what I'm trying to say. I did not mean that touchscreen could be touched with your hand when the water or the salt covered it. I experimented to see if the touchscreen reacts to the liquids, by putting several kinds of liquids in a non-conductive thin plastic bottle(Vial). The result was that when the liquid was water(or drink containing water such as coffee), glycerin, or ethanol, touch was possible but the screen did not work when the liquid was oil like gasoline or cooking oil. When tested in solid form, I I was possible to touch the screen with metal objects(such as locks, aluminum foil, even copper wire inside charger wires) , PE(on of the plastic) and solid salt in thin plastic containers, and in the case of most of non-conductive materials, such as solid sugar, plastic(except PE), cotton, rubber, paper and Calcium carbonate, touch was impossible. What I am wondering is, what is the criteria for the substances which makes the change of electric field?Another thing I am wondering is if it works by moving of the electrons from screen to substance changing the electric field of the screen, why does it work even when there is a non-conductive material between the finger and screen?I do not know if it was delivered properly, but I would really appreciate it if you answered it again!
The criteria for the substances to interact with the electrode is the conductivity. Conductive material like water, human body can interact with the touch screen, but plastic cannot. But being conductive is not enough, the conductor (e.g. human) must be able to couple to the sensing circuit by two ends, one end is the finger couple to the touch electrode by the small gap, and the other end the human body (or palm) to the ground plane by big surface area (watch 5:00). If you put a coin on your phone, it will not trigger because its like a finger without a body. The electrons cannot move from the screen/electrode to the substance. The physics is explained in 2:01. The electrode polarize the substance. The polarized substance in return attracts more electrons to the electrode, from the voltage source. BTW, the video is about surface capacitive sensor. Touch screen uses projected/mutual capacitive sensor. The physics behind surface and projected sensors are different, and the response is directly opposite. For example, a touch on surface capacitive sensor increases the capacitance, whereas a touch on project/mutual capacitance decreases the capacitance. I have another video on mutual capacitive sensor (ua-cam.com/video/gxLzgeiJQbE/v-deo.html). The video here is for surface capacitive sensor, and not directly applicable to touch screen (projected type), precisely speaking.
Hi EuAlex, Somehow your comment and my reply have disappeared, so i re-post here. If your signal is slower than a typical touch, but nevertheless is still substantially faster than the environmental drift, then you may have to implement your own algorithm in the MCU to differentiate the signal from the drift. IQS127D and IQS143 can be used as the analog front ends to measure the capacitance and send the raw data to the MCU serially for your own decision making algorithm.
I have an inquiry. Then I want to make something that can induce electrostatic induction in place of a person's fingertip. What principle can you make? How big a capacitor is needed? I wonder.
very interesting. Do you have an idea to use this system to measure the water level in a plastic water pipe diameter 25 mm and water column difference 50 mm ?
Hi. I have seen a stylus known as the high precision metal tip stylus for capacitive touchscreen. They have some sort os metal tip and are rechargable or has a aaa battery. Various brands link wacom, stilo, apex etc are available. Can u explain how do they work? I tried to search it on web for about 4-5 days but i got nothing. Will you please explain the working of that stylus? Thanks
Hey I have a question, So at min 1:55, what is exactly happening during the polarization process. How exactly does the polarized charges gain energy, or other way around if the plates losing potential and Why does the plates can receive more charges? What exactly is happening, (sorry im quite interested) Whats with the fingertip is changing the relative dielectric constant in the elecric field so we would have the formula C= A/d * er and er changes so the overall capacitance changes. good video
When charges are separated, they want to reunite and therefore they have the potential to do work. When the plates lose some potential, then the potential is lower then that of the battery, then charges flow from higher potential (battery) to lower potential (plates). After I made this video, i think a better explanation for the activities is based on the forces, not potential, because potential is a derived property from the force. When the object is polarized, the negative charges on the left side of the object (2:00) attract positive charges into the left plate (by e-field/force), and the positive charges on the right side of the object attract negative charges into the right plate.
To assume the the other plate is virtual ground means the ground plane is very big. To increase the sensitivity of the sensing plate, try to avoid ground plane directly underneath the sensing plate. This is to reduce the baseline capacitance, so that the change in capacitance is higher in terms of percentage.
Can you have mains wiring to a table an have 2 or more touch sensors sharing this? Maybe keyboard? If previous possible, can you also detect when bodies loses contact with given surfaces (sharing common mains wire)?
Hi, I would like to know whether the capacitance sensing mode you introduced belongs to the mutual capacitance mode? If it is self-capacitance sensing, how should we analyze it?
This video is about self-capacitive sensor. I have a video to analyse self capacitive sensor using lumped capacitor. I also have other video on mutual or projected capacitive sensor, in the same UA-cam channel. Thanks for watching.
@@SiliconSoup thanks for your explanation. But there's one thing I don't quite understand. In your video, at about 1 minute and 55 seconds, there are two other electrodes in addition to the target object.Shouldn't such a structure be mutually capacitive? I think if it is self-capacitive, there should be only one electrode acting as the sensor, and the object forms a capacitor with it. By the way, could you tell me which paper appears at 2 minutes and 45 seconds of the video?
@@伍攀-i1s There is no such thing as a one-plate capacitive sensor, as minimum two plates are needed to make a capacitor, and the object cannot be considered as one plate because it is not electrically connected to the circuit. The touch plate and the ground plane together form the sensor. Many people didn't know about the role of the ground plane in the sensing, and misunderstood that the touch plate is the only plate doing the sensing. This misunderstanding, has resulted in this sensor called the self-capacitive sensor. Strictly speaking, based on my academic knowledge on multi-conductor capacitor, the capacitance being sensed in the circuit is the mutual capacitance (so you are absolutely right), and this type of sensor should be called the mutual capacitive sensor. Another reason it is called the self-capacitive sensor, is from the implementation point of view; the charging of voltage and the sensing of induced charge happen on the same plate. The article is "The method of Moments in Electromagnetics", Massachusetts Institute of Technology, 6.635 lecture notes.
Hello! I am a high school student conducting research on this topic, and have some doubts I think you will be able to clarify. Please let me know if we can connect somehow. Thanks.
@@SiliconSoup Hey, I'm sorry if what I described was too long. Just email me on this id: cryptowriters@gmail.com. I don't use it much, and I'll delete the comment once you message me. Thanks.
The average power consumption of the sensor IC is the same, whether the object is near or far. Theoretically, in "charge transfer" method of capacitive sensing, object at further distance requires more transfer cycle to trip the sensor, so yes it take more power to sense object at further distance, but really not a consideration in engineering.
Ti me at 2:14, why does Capacitance increase untill the plate potential is back again?? i think that equibrilium is maintained strill after and would not be broken due to external object.... I'm really curious!!!
charges move from higher potential to lower potential. As more charges built up across the plates, the potential difference increases until it is the same as the voltage source and so a new equilibrium is established.
I also referred to application notes and datasheets from Azoteq, because the information is more practical than textbook. Yes, for this video, I used screen recording software. For newer videos, I output plots from the simulator directly to .gif file for animation, thus skipping the screen recording.
+Bo Cheng Mains wiring refers to 110V AC or 230V AC lines. Capacitive sensors in appliances are much more sensitive than those in handheld devices. The neutral wires increase the "ground plane" area, so it not only increase the sensitivity but also shift the sensitivity to the touch buttons.
+Pebble Soup Thanks for the explanation. Another question: I came across an issue that the trace where wiring the button to the controller also gets the sensitivity, in other word, the trace are also acting like switches. How do I decrease the sensitivity on the trace? (I tried added ground plane around it, shorten the spacing but it still didn't work well)
+Bo Cheng use the thinnest trace allowed by the PCB fabrication. This is to make the trace area much smaller than the touch pad area. If the touch pad is on the top side of the PCB, put the trace on the bottom side.
for self-capacitive sensor, the baseline capacitance should be small, so that the change of capacitance in percentage is big when the finger moves in. Any unwanted capacitance adding to the baseline is the parasitic capacitance. For example, a signal line underneath the sensing electrode is a parasitic capacitance. In fact, all metals in the circuit will form capacitance with the sensing electrode and are parasitic capacitance too. But due the far distance, the impact is not as big and signal lines underneath.
if you model your body as a perfect conductor, then when your finger moves relative to the touch sensor, charges on your body redistribute, but there is no gain or loss in energy, because no energy is required to move charges on a perfect conductor. If body resistance is taken into consideration, when your finger is near the sensor and your body is polarized, you gain energy (from the supply of the sensor). But when your finger moves away from the sensor, the polarized charges reunite through the body resistance and release energy through heat. This is academic fun :)
I applaud your knowledge and explanation, you are a great teacher!
Excellent production.
And practical too! This answers a number of questions about design considerations,
Thank you.
That was a FANTASTIC video! Great job showing the simulations and drawing practical conclusions!
I've been looking for this video!
Every source of information seeking to explain how theremins work through sheer circuit theory fails to explain the point around the 2 minute mark.
Surprisingly fantastic information I've been searching fro for years!
bravo, Bravo, BRAVO, B R A V O!!!! this is one of the best educational videos I've come across. Great explanation, great illustrations and given that it doesn't sound like English is your primary language, you knocked this video out of the park! I'm now your newest subscriber!
Thankyou gues best i liked all mdel ac ex interseted
First great video I found on the subject. Thx!
Looks like a highly recearch n informative type of communication engineering video..
Nice man
Awesome bro! Exactly what i needed to do my project! Much bless!
I must agree with all the comments. This is the best explanation and enhanced with demonstrative animation. Bravo! I look forward to seeing more of your posts. Thanks!
Wow, high quality production. Well-explained : )
Which touch IC are you using at 5:35 in the video?
Iqs127d from Azoteq
thanks for wonderful explanation using basic physics
Thanks for posting this! I've been looking for this information for a long time. I'm still looking for a rigorous evaluation of the physics of coplanar capacitors. The illustrations help, but I'd like to be able to calculate the values based on given dimensions. I've found a few equations on the web that come somewhat close, but I'd really like to derive the equation myself. If anybody can give me a push in the right direction (not off of a cliff please) I'd appreciate it a bunch:-)
Very nice video, I was looking for explanations like that, do you have any chip / IC numbers that can work with your design? thanks again
I used Azoteq IC to make the video. For single touch as an example, Azoteq offers IQS227. The theory I presented in the video works for all brands and implementations, whether it is the charge transfer or relaxation oscillation methods.
@@SiliconSoup Thank you very much, very nice of you
This is the best explenation i ever sean! Thnx!!!
Very good tips for DIY applications. Thanks !
Wow nice video. It explains a lot and with great detail
Very good explanation. We intended to use the IQS127D for one application where we currently use ATMEL. Only one doubt: In our application measured capacitance varies very smoothly, we are afraid that LTA functionality in AZOTEQ will adapt the sensitivity consequently missing then the detection.
Thank you so much for the great explanation!!
Well done, I think it could be better by illustrating a simple kirchhoff current loop though. There is a board capacitance to earth ground, a human capacitance to earth ground, and a human capacitance to the board (touching). This forms the basic loop for current to flow. When the ground plane of the board is big, the board capacitance is big and then only the touch capacitance matters. When the ground plane is small, the board capacitance is small and then it attenuates the touch capacitance. But yeah, good work anyways.
Thank you for such a great video .
Great explaination thank you!
Oh finally a reliable video
I just saw your response about dealing with environmental drift and I'm a bit confused. My understanding was to keep the sensing electrode as close to the capacitive controller as possible to eliminate this type of parasitic influence. Do those IC's condition the sensing electrode in some way? Or is this just another way to keep the connection between sensing electrode and controller as short as possible? Either way, I've always set the triggering threshold myself at the controller.
Magnificent video. Thank you!
I enjoyed your video. Thank you!
Thanks for the good video. One question: Is it possible to create large sensing areas for example 1m²?
The signal goes to the smaller plate. If the touch electrode is 1m^2, and the ground plane is smaller, a signal is produced when touching the ground plane (and NOT the electrode). If the ground plane is much bigger than the 1m^2, then the signal produced by touching the electrode will still be small, because the human body is well coupled to the electrode and ground plane to begin with, and moving the finger tip does not change in capacitor's geometry very much so the signal will still be very small.
Love this, thanks!
superb, so far urs best ...
Thank you. I'm flattered
I referred to the following materials for the classic "Method of Moment":
1) Harrington, R. F., Field Computation by Moment Methods, Macmillan, New York, 1968.
2) "The Method of Moments in Electromagnetics", MIT lecture notes, available on the internet (UA-cam don't let me put the link here)
3) "Numerical Solution for the Potential between Parallel Plates", Dr. David Jenn, nps.edu
I had to extend the formulation to 3- or 4-body system to include a person in the simulation.
Fantastic job explaining this! May I also contact you with some follow-up questions? I have been working on a very ambitious capacitive sensing project for the past year.
Hi, I am currently working on a capacitive proximity sensor, and I would like to ask you some questions.I placed a large sensor (with only one plate) vertically 40cm above the ground, and then tried to approach the sensor with a larger copper plate to observe the capacitance value and how it changed.I used COMSOL software to conduct simulation tests, in which the sensor was set far away from the target object. My original idea was to take the capacitance change obtained as the parallel plate capacitance between the sensor and the object, and calculate the distance value from this value, but I found that the inverse distance value was wrong, that is to say, the formula of parallel plate capacitor is not applicable in this case.So I wonder if you know of a more suitable theoretical model of capacitance.
How big is the plate? When you said 40cm above the ground, is that the electrical ground plane or ground we step on? Using one large plate will not work, because the working principle is that 2 plates sense the external object. The smaller plate has a higher sensitivity and the bigger plate has a lower sensitivity. The large plate you intend to use as the electrode will work against your intention. I demonstrated this surprising and unintuitive result in my other video "teardown of miband3". The equivalent circuit is shown in ua-cam.com/video/ZHzaVzYEZbw/v-deo.html. The circuit is simple, but it does predict bigger plate having smaller sensitivity and visi versa. The parallel plate model is incomplete. I hope this helps.
@@SiliconSoup The plate's area is 24cm*24cm.The ground is ground we step on.My intend is to achieve a long proximity distance,e.g. 50cm.This purpose requires the use of larger plates.
@@伍攀-i1s Firstly, is your circuit battery powered or AC powered (through DC-adapter)? If you circuit is AC powered, inherently the circuit ground is connected to the earth of the electrical system, so you already have a big ground plane, so together with the 24cm X 24cm electrode, they can sense any big object coming in between them. The object will have to be same or bigger size to make significant change to the capacitance. However, if you have a 24cm x 24cm electrode, and a small circuit ground (if the circuit is battery powered), then the circuit will not work as intended. In fact you will find the sensitivity goes to the circuit ground, the small plate. So what you need to do is to enlarge the circuit ground to an area comparable or larger than 24cm x 24cm. Again, I like to emphasize that the capacitance between the single plate and the object need a good return path back to the circuit for the capacitance to be detected, that the good return path is formed by a much bigger ground plane coupling to the object. If you are dealing of long distance, the signal change can be small, so you need a sensitive capacitive sensing IC. Not all sensing IC have good SNR. I strongly recommend azoteq, because I experimented with it, and it is really good.
Hello. Thanks for the very good video. Can you recommend a book on that topic? You show some single figures and pages from different books in the video.
By the way: Did you use a screen recording sodtware? Loos great!
Best regards
Manuel
I'm very encouraged by the feedback. Thanks.
I've made another video about the projected capacitive sensor. I hope it is educational and useful.
Wow, I am blown away. Such care for editing and animation, so simply explained, from a small channel. Thank you, I will use it in my current project!
Hi, a great explaining video..!
Are the sources, like the papers and Matlab models available for download or purchase?
I used Azoteq IQS222 and IQS127D for experiment. The sensitivity and stability are really good. The information about the eval-kits, including where to buy, is in their website.
In capacitive sensing, two electrodes (one is the circuit ground, the other is the touch electrode) are required to complete the sensing path, and the signal (delta C) has a bigger change at the smaller electrode. A big table will increase the signal level at other (smaller) electrodes, but the table itself will produce very weak signal and can't be use and the sensing electrode. /watch?v=ZHzaVzYEZbw in UA-cam.
Excellent video....Thank you!
You are genius.
Super! Thank you very much!
In TTP223, if I make the ground pad smaller and the touch pad bigger, the sensitivity does not transfer to the ground pad. Why doesn't TTP223 follow that?
The ground is not just the pcb ground, but includes the battery ground or earth from the mains. If the battery is big, or the emulator has connection to PC ground,, or the DC adaptor is coupled to the earth, then the total ground is big, and the sensitivity is on the touch pad. The sensitivity is shifted to the touch pad when the device is powered by small batteries.
Awesome refresher!
Very good video for PCS.
how to fake a touch using electronics like those shoulder buttons used to play mobile games like pubg and they press like 10x a second
it uses capair capastive mapping technology what is that?
thank you for such a great video
very underrated, perfect
Much appreciated! Thank you
Very good video!!!
Thanks I now know much more abt cap. Sensors.
I'm happy the video is useful.
excellent video! Thank you.
Nice lesson
Permit to download this video.
Thanks
Can we use a capacitor to determine two different fluids with different polarities?
Hello! I'm 18 years old student in Korea. I researched on the principle of capacitive touch screen and the criteria of the substance that detects the input, several months ago. This is because it was interesting to know that touchscreen even works with materials such as water, salt, and polyethylene. I was able to find out some information about touchscreen, however, it is hard to find any more information about it on the Korean internetT.T
If you have any facts about substance that enables capacitive touchscreen to work, please help me... I'll will wait for the reply!
The electrodes that detect the capacitance must be conductive, e.g. copper or ITO (Indium Tin Oxide). The gap between the electrode and the finger must be non-conductive, such as air, acrylic, glass, because electric field can pass through this media. Water, salt-water, aluminium cover are conductive and block the e-field and therefore should not sit in between the electrode and finger. Of course, a little bit of water on the cover will not block the e-field fully, so capacitive sensing is still possible, if the circuit is very sensitive.
@@SiliconSoup Thank you for your kind reply! I was overjoyed this morning. But I still have something that I can't understand. I think I had not been able to convey the meaning of what I'm trying to say. I did not mean that touchscreen could be touched with your hand when the water or the salt covered it. I experimented to see if the touchscreen reacts to the liquids, by putting several kinds of liquids in a non-conductive thin plastic bottle(Vial). The result was that when the liquid was water(or drink containing water such as coffee), glycerin, or ethanol, touch was possible but the screen did not work when the liquid was oil like gasoline or cooking oil. When tested in solid form, I I was possible to touch the screen with metal objects(such as locks, aluminum foil, even copper wire inside charger wires) , PE(on of the plastic) and solid salt in thin plastic containers, and in the case of most of non-conductive materials, such as solid sugar, plastic(except PE), cotton, rubber, paper and Calcium carbonate, touch was impossible. What I am wondering is, what is the criteria for the substances which makes the change of electric field?Another thing I am wondering is if it works by moving of the electrons from screen to substance changing the electric field of the screen, why does it work even when there is a non-conductive material between the finger and screen?I do not know if it was delivered properly, but I would really appreciate it if you answered it again!
The criteria for the substances to interact with the electrode is the conductivity. Conductive material like water, human body can interact with the touch screen, but plastic cannot. But being conductive is not enough, the conductor (e.g. human) must be able to couple to the sensing circuit by two ends, one end is the finger couple to the touch electrode by the small gap, and the other end the human body (or palm) to the ground plane by big surface area (watch 5:00). If you put a coin on your phone, it will not trigger because its like a finger without a body.
The electrons cannot move from the screen/electrode to the substance. The physics is explained in 2:01. The electrode polarize the substance. The polarized substance in return attracts more electrons to the electrode, from the voltage source.
BTW, the video is about surface capacitive sensor. Touch screen uses projected/mutual capacitive sensor. The physics behind surface and projected sensors are different, and the response is directly opposite. For example, a touch on surface capacitive sensor increases the capacitance, whereas a touch on project/mutual capacitance decreases the capacitance.
I have another video on mutual capacitive sensor (ua-cam.com/video/gxLzgeiJQbE/v-deo.html). The video here is for surface capacitive sensor, and not directly applicable to touch screen (projected type), precisely speaking.
Hi EuAlex,
Somehow your comment and my reply have disappeared, so i re-post here.
If your signal is slower than a typical touch, but nevertheless is still substantially faster than the environmental drift, then you may have to implement your own algorithm in the MCU to differentiate the signal from the drift. IQS127D and IQS143 can be used as the analog front ends to measure the capacitance and send the raw data to the MCU serially for your own decision making algorithm.
I have an inquiry.
Then I want to make something that can induce electrostatic induction in place of a person's fingertip.
What principle can you make?
How big a capacitor is needed?
I wonder.
very interesting. Do you have an idea to use this system to measure the water level in a plastic water pipe diameter 25 mm and water column difference 50 mm ?
Hi.
I have seen a stylus known as the high precision metal tip stylus for capacitive touchscreen.
They have some sort os metal tip and are rechargable or has a aaa battery.
Various brands link wacom, stilo, apex etc are available.
Can u explain how do they work?
I tried to search it on web for about 4-5 days but i got nothing.
Will you please explain the working of that stylus?
Thanks
Could you tell me where I can find the analytical solution for the coplanar capacitors?
Hey I have a question,
So at min 1:55, what is exactly happening during the polarization process. How exactly does the polarized charges gain energy, or other way around if the plates losing potential and Why does the plates can receive more charges?
What exactly is happening, (sorry im quite interested)
Whats with the fingertip is changing the relative dielectric constant in the elecric field so we would have the formula C= A/d * er and er changes so the overall capacitance changes.
good video
When charges are separated, they want to reunite and therefore they have the potential to do work. When the plates lose some potential, then the potential is lower then that of the battery, then charges flow from higher potential (battery) to lower potential (plates).
After I made this video, i think a better explanation for the activities is based on the forces, not potential, because potential is a derived property from the force. When the object is polarized, the negative charges on the left side of the object (2:00) attract positive charges into the left plate (by e-field/force), and the positive charges on the right side of the object attract negative charges into the right plate.
Thanks a lot, i really appreciate your quick and detailed answer ;)
Nice Video, I want to know how to increase in a single plate capacitor assuming the other one is virtual ground.
To assume the the other plate is virtual ground means the ground plane is very big. To increase the sensitivity of the sensing plate, try to avoid ground plane directly underneath the sensing plate. This is to reduce the baseline capacitance, so that the change in capacitance is higher in terms of percentage.
Can you have mains wiring to a table an have 2 or more touch sensors sharing this? Maybe keyboard? If previous possible, can you also detect when bodies loses contact with given surfaces (sharing common mains wire)?
Hi, I would like to know whether the capacitance sensing mode you introduced belongs to the mutual capacitance mode?
If it is self-capacitance sensing, how should we analyze it?
This video is about self-capacitive sensor. I have a video to analyse self capacitive sensor using lumped capacitor. I also have other video on mutual or projected capacitive sensor, in the same UA-cam channel. Thanks for watching.
@@SiliconSoup thanks for your explanation. But there's one thing I don't quite understand.
In your video, at about 1 minute and 55 seconds, there are two other electrodes in addition to the target object.Shouldn't such a structure be mutually capacitive? I think if it is self-capacitive, there should be only one electrode acting as the sensor, and the object forms a capacitor with it.
By the way, could you tell me which paper appears at 2 minutes and 45 seconds of the video?
@@伍攀-i1s There is no such thing as a one-plate capacitive sensor, as minimum two plates are needed to make a capacitor, and the object cannot be considered as one plate because it is not electrically connected to the circuit. The touch plate and the ground plane together form the sensor. Many people didn't know about the role of the ground plane in the sensing, and misunderstood that the touch plate is the only plate doing the sensing. This misunderstanding, has resulted in this sensor called the self-capacitive sensor. Strictly speaking, based on my academic knowledge on multi-conductor capacitor, the capacitance being sensed in the circuit is the mutual capacitance (so you are absolutely right), and this type of sensor should be called the mutual capacitive sensor. Another reason it is called the self-capacitive sensor, is from the implementation point of view; the charging of voltage and the sensing of induced charge happen on the same plate. The article is "The method of Moments in Electromagnetics", Massachusetts Institute of Technology, 6.635 lecture notes.
Can you be contacted to take a design commission?
What did you use to make the circuit at 5:35?
Hello! I am a high school student conducting research on this topic, and have some doubts I think you will be able to clarify. Please let me know if we can connect somehow. Thanks.
Yes, we can always discuss about this topic. I am not sure how to give you my gmail address without publicly reveal it here. We can discuss here too.
@@SiliconSoup Hey, I'm sorry if what I described was too long. Just email me on this id: cryptowriters@gmail.com. I don't use it much, and I'll delete the comment once you message me. Thanks.
Great video!
Hi to detect a distance of an object from a capacitance sensor, is more power required to detect the object being further away?
The average power consumption of the sensor IC is the same, whether the object is near or far. Theoretically, in "charge transfer" method of capacitive sensing, object at further distance requires more transfer cycle to trip the sensor, so yes it take more power to sense object at further distance, but really not a consideration in engineering.
@@SiliconSoup thanks so much!! Just for my understanding of the concept
Thank you so much
Very nice!
Super great.
great work
bless u my friend
Ti me at 2:14, why does Capacitance increase untill the plate potential is back again?? i think that equibrilium is maintained strill after and would not be broken due to external object.... I'm really curious!!!
charges move from higher potential to lower potential. As more charges built up across the plates, the potential difference increases until it is the same as the voltage source and so a new equilibrium is established.
Pebble Soup
Nice one
helpfull technology for elctrical products
i am finally beginning to understand but its quite complex.
I also referred to application notes and datasheets from Azoteq, because the information is more practical than textbook.
Yes, for this video, I used screen recording software. For newer videos, I output plots from the simulator directly to .gif file for animation, thus skipping the screen recording.
it is used in aircraft fuel quantity measurement also right???
+Michelle Ang Capacitive sensor can be used for measuring liquid level, but I am not sure whether it is actually used for aircraft fuel.
i saw the same person with same comment in some other links too!
good knowledge
6:22, mentioned Mains Wiring, what does tat refer to?
+Bo Cheng
Mains wiring refers to 110V AC or 230V AC lines. Capacitive sensors in appliances are much more sensitive than those in handheld devices. The neutral wires increase the "ground plane" area, so it not only increase the sensitivity but also shift the sensitivity to the touch buttons.
+Pebble Soup Thanks for the explanation.
Another question: I came across an issue that the trace where wiring the button to the controller also gets the sensitivity, in other word, the trace are also acting like switches. How do I decrease the sensitivity on the trace? (I tried added ground plane around it, shorten the spacing but it still didn't work well)
+Bo Cheng use the thinnest trace allowed by the PCB fabrication. This is to make the trace area much smaller than the touch pad area. If the touch pad is on the top side of the PCB, put the trace on the bottom side.
what is the product shown on 2:23?
It is a demo set that uses very sensitive capacitive sensors to control the RGB LEDs.
so good thanks.
Thanks!
do you have github account need the py data
what is parasitic capacitance?
for self-capacitive sensor, the baseline capacitance should be small, so that the change of capacitance in percentage is big when the finger moves in. Any unwanted capacitance adding to the baseline is the parasitic capacitance. For example, a signal line underneath the sensing electrode is a parasitic capacitance. In fact, all metals in the circuit will form capacitance with the sensing electrode and are parasitic capacitance too. But due the far distance, the impact is not as big and signal lines underneath.
Good sharing. Cheok!
so am i losing energy by touching a screen????????????????????????????????????????
if you model your body as a perfect conductor, then when your finger moves relative to the touch sensor, charges on your body redistribute, but there is no gain or loss in energy, because no energy is required to move charges on a perfect conductor. If body resistance is taken into consideration, when your finger is near the sensor and your body is polarized, you gain energy (from the supply of the sensor). But when your finger moves away from the sensor, the polarized charges reunite through the body resistance and release energy through heat. This is academic fun :)
Lousy clipart, great physics lesson :)
Em accent ra babu