Questions tagged [capacitive]

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Do projected capacitive touch panels need side clearance to ground metal?

I need to use a TFT module with an integrated capacitive touch. The TFT has it's FFC and the touch controller has its own, with power supply and an I2C interface. Quite standard, I think, since every ...
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2 answers
69 views

How do self capacitance touch screens work?

I get how mutual capacitance touch screens work, by changing the dielectric around the pairs of electrode and "stealing" electric field lines. Connection to earth of the object (a finger ...
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Using capacitive touch screen without human hand

I'm trying to learn more about how to engage a capacitive touchscreen without using a human finger. Full disclaimer I'm in mechanical engineering (notoriously known to have difficulty comprehending ...
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Choosing component values for capacitive accelerometer readout-circuit

I am trying to design and simulate a capacitive accelerometer. The idea is to model the sensor as a capacitance bridge to which an AC signal is inserted. Each arm of the bridge acts as a voltage ...
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Inductive or capacitive load?

Here I have a series LCR circuit with resonant frequency greater than 200Hz. Is there a way to know whether this circuit is an inductive or a capacitive load? Edit: The only additional information we ...
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2 answers
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Differential capacitive transducer

I would like to design a differential capacitive transducer to measure the capacitance change in an accelerometer. I cant seem to understand, how to demodulate the signal and keep the actual DC value....
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1 answer
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How to know if an opamp can drive capacitive loads?

There has been a lot of questions about how to stablise opamp circuits driving capacitive loads. However, I know there are some op amps that are designed to drive capacitive loads but I am struggling ...
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2 answers
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Help with capacitive touch button output configuration

Can someone help me with the basic working of this capacitive touch switch? I know it isn't very complicated but I just can't get over my brain block of what actually triggers when the button is ...
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4 answers
83 views

sensitivity and frequency-stability of capacitor-based oscillator circuit

I am constructing a capacitive transducer which changes capacitance as a function of changes in other physical properties. The capacitance is about 0.1~0.5 nF range, and I want to detect about 0.05% ...
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3 votes
1 answer
127 views

How do capacitive touchscreens really work?

I have a bit of trouble understanding the electrical laws which apply when I touch a capacitive touchscreen with my finger. Apparently, there is an electric current running through electrodes below ...
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2 answers
78 views

Bypass touch sensor IC with a button?

I want to replace a capacitive touch sensor on a circuit board (I think it’s a TTP223) with a tactile switch to overcome over/under sensitivity issues. I have wired a switch to ground and the CMOS ...
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1 answer
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Sensor to detect collision or intervention

I am currently working on a project (robotic arm) where I need to detect human collision with the robot. I need a sensor that should be flexible, detect human intervention in the workspace of the ...
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1 answer
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Pre-charge resistor and contactor power dissipation calculation

I am building my e-motorcycle. I am planning to use only one contactor instead of using three contactors. In my plan, pre-charge resistor and contactor circuit will be main contactor too. I am curious ...
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Correct design of capsense controls

I am trying to design a PCB with some capacitive controls. My first iteration did not seem to work well: This was a 2-layer 1.6mm board with one circular control, and 5 buttons. The board is 48mm ...
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People detection in large rooms using antennas

After coming across a 2004 installation by Carsten Nicolai titled "anti" where he used a theremin as an element for presence sensing, I was wondering if this principle could be extended to ...
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Capacitive load in inverter

I'm trying to understand the effect of a capacitive load at the output of an inverter. And how does it affect the output signal when this capacitive load is high and when it is low? Could anybody ...
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1 answer
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How to detect which finger touched the mobile screen [closed]

I'm working on a project where I need to detect which finger touched the mobile screen i.e capacitive screen. I'm not talking about double finger touch or single or drag and move etc. I'm asking which ...
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1 answer
101 views

Capacitive voltage divider question

I see a few discussions on this but cannot really find the "definitive" answer. I am building an audio amp and have two modules, one requires 18-0-18V AC and the other 12-0V AC, the 12V ...
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1 vote
3 answers
379 views

Bad capacitive touch screen sensitivity when running on battery, without earth

In short: I´m working on a battery driven handheld device with capacitive-touch screen. The capacitive-touch works perfect when the PCB connected via USB, but it loses sensitivity when driven by ...
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Adjustable voltage, 1 MHz capacitive biasing

I'm a budding physicist with little electronic design experience and am interested in driving an alternating E-field of adjustable strength within capacitive loads. Buying a several thousand dollar ...
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2 answers
54 views

LED on lamp outlet flashes when switch is off - is this capacitive coupling charging the power supply? And what to do about it? [closed]

I wanted to connect an LED light chain to a lamp outlet in my house in order to turn it on and off using the wall light switch. I have dismantled the 230V to 3V power supply that was built into the ...
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Soft-start design and performant with short-circuit test

I am working on a soft-start for a capacitive load. I using module QSB40024S24 to create 24V output. At first, I allowed the output of the module to connect directly to a capacitor array (21.4mF in ...
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1 answer
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Calculate -3db point in low pass inverting transistor audio amplifier

What I am trying to do: I am looking to find the \$ -3dB \$ frequency for my common emitter transistor amplifier with a capacitor in the feedback loop. I have somewhat of an idea, but I wanted someone ...
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3 answers
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Capacitive load of connecting cable for a temperature sensor

An LM35 temperature sensor is 4m removed from the Arduino to connect it too. The available cable has 4 wires with a diameter of 0.6mm (0.28 mm2 area) as well as a, seemingly aluminum, shield . The ...
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Capacitive touch sensor senses every materials touch

I have a ttp223 capacitive touch sensor. It has three pins, VCC GND and I/O. I left I/O open for test purposes. I connected the VCC to 5V and GND to ground. When I touch the sensor, its led indicator ...
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Grove capacitive fingerprint sensor not working

I have just purchased one grove capacitive finger print sensor. link. I am using Arduino Nano and followed there tutorial but the example code isn’t working. Blue light on sensor never turn to green ...
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1 vote
1 answer
119 views

How to detect which pins on a pin display are touched using capacitive sensing

I'm working on a project to apply touch sensitivity to a modified pin display (30x30). The goal is to allow someone to interact with the display through their fingers and ideally touch. We initially ...
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1 answer
60 views

Capacitor 250V DC

I have 0.22uF 250V DC MLCC SMD capacitor. Can I use it for 230V AC main as capacitive power supply? Your suggestion will be helpful for me.
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1 answer
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Different battery capacities in series is poor

How is the scientific (electrochemistry, physics, electrical, etc) explanation on different battery capacities in series is bad or poor and will damage them ?
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40 votes
10 answers
4k views

How can human finger pressure be measured?

I am dealing with a situation where a patient can only very lightly press his fingers / hand to signal what he / she wants. Speaking or eye tracking is not possible. The person is also not able to ...
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3 votes
0 answers
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High-side mosfet switch placement

this is a power circuit I'm trying to complete: the button at top turns the curcuit on, supplying VCC to mcu, and the MCU will output a high signal to a pin (marked in pink) which turns the N-MOSFET ...
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1 vote
1 answer
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Why are parasitic capacitances the main factor for limiting high frequency performance of active devices such as transistors? [closed]

According to the Wikipedia article, the reason for the limit of frequencies in which transistors operate is the parasitic capacitance. But I don't understand why this is so. Wikipedia article: ...
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2 answers
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Finding the kVA loading after improving the power factor

This is a homework question I've been attempting. But the answer I get doesn't match with whats given and I don't understand why my method is wrong. This is the question with answers. Here's what I'...
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1 vote
1 answer
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Capacitive Touch Faucet Solenoid Battery Box vs AC/DC adapter [closed]

I have a MSTJRY touch kitchen faucet purchased through Amazon. It uses a valve solenoid in line with the water supply to control the on/off of the faucet based on capacitive touch on the faucet stem. ...
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TTP223 capacitive sensor on USB switch takes two presses to work

I'm trying to solder a TTP223 capacitive touch sensor to a USB switch (specifically a "UGREEN USB 3.0 Switch, 2 In 4 Output") to rig a sort of capacitive KVM switch to a desk PC I'm building,...
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1 answer
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How to properly drive parallel analog switches (variable capacitive loads) with opamp(s)?

So as you can see I have 16 SPDT switches on one side of my 16 'RUT paths' and 16 SPDTs on the other side. Each SPDT(ADG1434) has two source pins (SXA and SXB) and a common drain pin (DX), 'X' ...
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1 answer
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Capacitive touch sense problem with battery powered laptop

I designed a PCB that includes capacitive touch. The circuit works with 5V powered from USB. When Laptop is connected to 220V line, the PIC can sense capacitance variation. When Laptop is not ...
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2 votes
0 answers
51 views

Capacitive Touch Pad Design with TTP224 ic

I am designing circular capacitive touch pads of Dia:20mm driving from TTP224 IC on my PCB. There will be 2mm glass panel above Touch pads. My PCB contains other circuits like Arduino, Antenna bands ...
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-1 votes
2 answers
100 views

How to make sure that my compensated attenuator would work for certain pulse widths?

I have an input (one-shot) pulse that has to be attenuated by 1/2 (half). The input pulse would be of variable width in between 1us and 100ms and would have a variable amplitude: one voltage level ...
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1 answer
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Test device for capacitive touch screens?

Are there any (more or less) simple test devices for capacitive touch screens, e.g. something which I can attach to a touch screen and which is able to do capacitive inputs at fixed locations (ideally,...
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0 votes
1 answer
697 views

Reverse-engineer pinout of capacitive touchscreen

I'm interested in reusing the capacitive touchscreen of my old iPad. (As a learning experience -- I'm aware that this project will cost me more than just buying a new capacitive touchscreen would.) ...
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0 answers
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Variac and Other dropper in line

I have a beautiful old variac, with a sliding (rotating) center contact. I would love to use this on a nice LED string inside a glass bulb on top of the device. But also, use the variac as the dimmer, ...
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Distribution of charges in an electrostatic study

I have a question concerning the capacitive coupling between two conductors. The capacitance C between the two is only a function of the diameter of the 2 studied conductors, the insulation thickness ...
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1 vote
0 answers
27 views

How to improve capactive sensor when there is a floating local ground [duplicate]

I am using a microchip MTCH101 IC as a proximity detector (based on a self-capacitance electrode) and i have some trouble in detection because of a floating local ground (i guess). The sensor is power ...
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1 vote
4 answers
785 views

ESP32 touch sensor outputs unstable values

I am trying to implement touch functionality of esp32 development board to toggle a led. But on uploading a simple touch detection sketch, output have spikes i.e. usually value remains near 100 but ...
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1 vote
1 answer
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Capacitive medium range sensor with STM8

I am trying to replicate the behaviour of this library: https://playground.arduino.cc/Main/CapacitiveSensor/ with an STM8, but I am not able to do it. I want to detect the proximity of the human hand ...
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1 vote
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Waterproof capacitive touch-sensor issue

my goal is to develop a waterproof capacitive touch-sensor. In many sources on the internet, it is said that a mutual-capacitance sensor can achieve this. For example, in the TI Designs: TIDM-1021 ...
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What material can I use to block a capacitive touch from registering?

I am a self proclaimed tinkering problem solver, but this one has me absolutely stumped! I have a capacitive touch switch panel with six touch areas that close or open a relay to supply power to ...
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1 vote
3 answers
436 views

How to make fast (low latency) capacitive touch buttons

I'm looking to create low latency capacitive touch buttons for a musical instrument. The response time (from physical touch to touch registered in microcontroller) needs to be around ~2ms or less. ...
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1 vote
1 answer
63 views

How is this LCD controlled?

Source: https://ozhealth.com.sg/product/genial-digital-thermometer-t15-orange/ I tore down a digital thermometer today (a Genial T15), and the interface to the LCD caught my eye: although there were ...
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