Questions tagged [capacitive]

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capacitive reactance in a stranded wire

Can a stranded wire exhibit a capacitive reactance? I measured the real and imaginary part of a piece stranded wire using an old LRC meter( HP 4284a). Applied an open loop and a closed loop ...
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1answer
476 views

Capacitive sensor as drop-in replacement for mechanical button

I have a device X (talking toy), which has a jack of two wires for an external button. That is, I can short the two wires and device X accepts it as a press of a button. Now, I want to use device X ...
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3k views

ATtiny13a capacitive power supply

I would like to power my Attiny13a MCU with a transformerless capacitive power supply. The MCU itself needs only a few milli amps and it will drive 2 LEDs at 15mA each through it's digital pins. So I ...
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1answer
230 views

Figuring out the protocol of an SPI device without a datasheet

I am pondering about interfacing with the iPad Mini 2 touch panel. It seems that no one has successfully done this and/or published anything about it, so I want to take a stab at it. As far as I ...
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4answers
1k views

Capacitance on the output of an op amp

I have read a lot about capacitive loads on the output of an op-amp and the possibility of unwanted oscillations and instability. my knowledge on phase margin and frequency domain analysis is a little ...
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1answer
807 views

Modelling a “scope probes' acting as an antenna” phenomenon in a circuit

Here below I draw a simplistic model for stray capacitance issue in SMPSs: Basically pF level Y capacitor across the AC line forms an RC voltage divider when measured by a voltmeter with respect to ...
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1k views

How can I fool an auto-calibrating capacitive touch sensor?

I have a MicroBot Push - looks like this: Below the blue ring on the top is a capacitive touch pad and a TTP223-BA6 controller. Here's what it looks like under the hood. It's a long story, but I ...
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2answers
919 views

capacitive sensing PCB overlay

reading some of the capacitive sensing IC datasheets around, they always recommend an isolation overlay over the sensor pad. Like this: I'm wondering, why not use the actual PCB as overlay? like ...
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1answer
314 views

Design of capacitive proximity sensor

I am currently designing a microgripper for which I need a proximity/distance sensor. Please refer to the image below for design requirements. Due to the force application (as shown in the image), ...
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1answer
1k views

Capacitive touch screen sensitivity question

I have a question about capacitive touch sensing. I have read a few related questions already (here, here and here) and I think I understand the basics. From my understanding, when a human uses a ...
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1answer
83 views

Is it a disadvantage for a generator to supply both resistive and reactive current to its load?

Suppose The power network 1 has a resistive load and therefore the current supplied by the generator 1 to the load is purely resistive. The power network 2 has a resistive + inductive load and ...
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54 views

Rugged Capacitive Single Touch Screen

I am looking to make a capacitive single touch screen into a small table. Which I can use to put coffee cup etc on. It does not have to be waterproof but rugged enough to not scratch over time easily ...
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1answer
1k views

Marvell PHY to KS8999 PHY connection

I'm trying to design a custom board with Marvell 88E1111 PHY and I want to connect this board to another board with KS8999 PHY on it. I want to connect two phy sides with capacitive coupling. The ...
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166 views

Peak value of sine wave for capacitively coupled inverting amplifier

I was working on question 2.23(a) and there is asked what input voltage is needed in order to ensure that the output does not clip. The clipping limits are +10 to -10 V. I solved that, and, ...
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1answer
258 views

Digital control over capacitive touch

I would like to generate computer controlled touches on a capacitive touch screen (e.g. iphone) using the following setup: I have a conductive patch (size of finger) that I place on the touchscreen ...
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1answer
222 views

Capacitive projectile triggering touch screen

I've read through a number of questions (How can a capacitive touch screen be triggered without human contact?), (How to use a capacitive touch screen without a human hand), (What is the minimal ...
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1answer
752 views

PCB stackup for capacitive buttons, LEDs and other components

The design I am working on has about 30 capacitive buttons, LEDs for back-lighting, about 8-10 ICs (capsense controllers, LED drivers, MCU, etc), many passive components and coin cell batteries. I am ...
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1answer
400 views

Capacitive proximity sensor size?

I want to design a capacitive proximity sensor to detect human presence at a distance of 10-15 cm. Now I made my research on this type of sensor but everything that i found doesn't tell me about the ...
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2answers
1k views

Why power factor correction for Capacitive load is more difficult?

When we want to correction power factor of a motor(inductive load) its simply can done by adding an capacitor in parallel with the motor but its not possible to correction power factor of an ...
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1answer
2k views

Eliminating ghost voltage and breaking ground loops in a system

The above illustration is a setup I use where amplifier outputs go to a data acquisition system through BNC cables. The data acquisition system is earth-grounded. Mains system voltage Line to Neutral ...
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134 views

Capacitive sensor - How to activate with a portable device

I'd like to activate a capacitive sensor - a smartphone touch screen for instance - with an electronic device - say an Arduino board. Basically I'd like to reproduce this instructable, but with one ...
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1answer
218 views

Capacitive sensing with large distance

I am curious on how capacitive sensing work. How does it sense hand gesture, or measure water level when the distance between the capacitance plates are large (5-10cm)? I thought that capacitance ...
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1answer
245 views

Differential CVD waveform in PIC18F45K50

I am using PIC18f45K50 for capacitive touch button using a differential CVD. My capacitive button works. However I am not able to get the standard differential CVD waveform suggested by Microchip. Has ...
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2answers
405 views

Wall touch switch design

How can I make a capacitive wall touch switch? remembering that the wall standard light switch has just two wires for close the circuit. How can I supply my circuit when the light is on in order to ...
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2answers
396 views

How does the glass screen of smart phones not block the discharge of capacitors in capacitive touch screens?

Glass is one of the best insulators when designing high voltage electronics, and correct me if I'm wrong, but capacitive touch screens work by measuring the charge of capacitors in a grid on the ...
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200 views

Capacitive Touch Screen Stylus circuit type of thing

I am trying to figure out how to make a circuit that works much like a stylus for capacitive touch screens such as on an iPhone. Given it's going to be a simple experiment, I was thinking of using an ...
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1answer
63k views

How do I find C & L from XC and XL?

Calculating Capacitance and Inductance from Capacitive Reactance and Inductive Reactance I'm trying to find the inductor (L) and capacitor (C) values using the inductive reactance (XL) and capacitive ...
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4answers
2k views

Relay contact sticking while driving a capacitive load

I am using a Panasonic relay (ALQ105) rated for a resistive load of 10 amps 5A at 250V to drive LED bulbs. These LEDs have capacitive circuits in their ballasts and hence draw high inrush current when ...
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3answers
325 views

Is electric field of capacitive sensing circuit harmful and is it radiation?

I have constructed a circuit for capacitive sensing. The code charges and discharges a conductive plate. This uses an Arduino which is connected to a computer via USB. I have decided to measure the ...
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0answers
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Capacitive touch sensor design

I made a PCB with several capacitive pads to be read by IQS127. They work, but any material I put close to the PCB surface will trigger the output, even the 8 mm glass I'm going to use. The pads ...
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1answer
177 views

capacitive touch film or integerated capacitive touch panel display? using under glass [closed]

We need to put display under 2mm glass. Our device must have capacitive touch input. which method should we use? Capacitive Touch Films (place it under glass) or LCDs with integrated capacitive touch (...
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1answer
2k views

PCB trace capacitance

I am designing a capacitive touch keypad using cypress MBR series. The design guide has an excel spreadsheet to help with max trace length and button dia requirements. The idea is to keep the button + ...
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2answers
2k views

Electrically simulate and toggle a capacitive touch

I am interested in testing a capacitive touch device for reliability by simulating touch events periodically. I would like to do this purely electrically if possible (no mechanical parts), or with a ...
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3answers
465 views

Sensing the capacitance value of a material - for an ID system

This is a follow up question to 'How does a Capacitive ID / Signatures / Sensing system work? e.g. Google Bloks' In the 'Google Bloks' project. A tangible programming experience is created by ...
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1answer
167 views

How does a Capacitive ID / Signatures / Sensing system work? e.g. Google Bloks

In the 'Google Bloks' project. A tangible programming experience is created by allowing children to place physical instruction blocks next to each other. The computer is able to read the sequence ...
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1answer
264 views

Elegant non-mechanical way to switch on battery-powered device the first time

For a primary-battery powered device, that will be stored for a period of time before first use, what is the most elegant non-mechanical* way to switch it on for the first time, after which it will ...
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2answers
203 views

Minimizing capacitive crosstalk in open collector quadrature speed sensor

I am integrating a speed sensor (Honeywell SNDH-T4L-G01) which comprises 4 lines: VDD, VSS, A, B. The last two signals provide speed and direction information in a quadrature format. These are open ...
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1answer
740 views

Water level capacitive probe topology

I'm building a small capacitive water level sensor for a reservoir (16cm tall x 10cm x 7cm). This prototype gives me 10pF on free air and 20~30pF on medium water levels, so its definetively doable (...
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1answer
1k views

Capacitive Coupling Between Adjacent Conductors

I have been unable to find a definitive answer to my questions after some extensive browsing online. My question involves the coupling between two adjacent conductors (wires, PCB traces, etc) due to ...
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1answer
594 views

Heartrate measuring using capacitive touch sensor

I am new here, and I hope someone could help me. So I've read in the datasheet of the capacitive touch sensor ATMEL42QT1011 that we could use it as a heart rate sensor.But what I don't understand is ...
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2answers
164 views

Simple short range object proximity identification using capacitive sensing

I'm designign a device capable to sense proximity with other identintical devices and communicate that to a central node via bluetooth. The problem I'm trying to solve is showed in figure. So far I ...
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1answer
5k views

Homemade shielding of a wire to a capacitive sensor

I'm using a capacitive sensor CAP1188 with Arduino, connecting 8 of its touch sensor inputs to 8 copper boards that I want to be the actual touch surfaces. The wires to the sensor are quite long (100 ...
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1answer
843 views

Capacitive touch switches drop voltage and limits current

Bought two different touch switches/devices to toggle outputs to other devices. I use this on USB power so input is 5V. With use of a powerpack it can handle 2A max. NOTICE: Ask my question here ...
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2answers
3k views

capacitive switch behind a mirror (silver backing)

I am new to this field, and I would like to DIY a mirror with a hidden capacitive \inductive touch sensor behind it, once touched it will turn on a 12V LED light. I have bought a capacitive switch ...
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2answers
1k views

Grid is capacitive in the evening

what does this term mean? "the grid in the evening is capacitive"? I work at a company and we are working on integrating a battery storage system on a utility scale for peak shaving of solar. When we ...
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1answer
1k views

How to obtain the transfer function of the capacitive sensor?

I want to obtain the transfer function of this capacitive sensor which in the circuit, C is the variable capacitor that transforms displacement to electrical signal and E is the dc voltage source ...
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1answer
3k views

Convert capacitive touch sensing back to mechanical switches?

Capacitive sensing seems to replace often mechanical switches. Is there a way to convert them back to mechanical switches? Problem at hand is a cooking device with interfaces with the user via the ...
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1answer
2k views

How does capacitive EEG electrodes measures EEG signals

I have read the following sentences from an article: The effect that there are also charge displacements on the body surface due to brain activity is used for the capacitive measurement of the ...
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1answer
616 views

Capacitive Moisture Sensor - Is AC or DC better/more accurate?

I am looking into making a capacitive moisture sensor. This has been discussed many times already, but I am not sure what is the better option, AC or DC. I want to run this off of a battery, so DC ...
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1answer
893 views

Which MCU (Atmel) I can use with QTouch library?

Some MCU have QTouch support - # touch channels implemented as a hardware. Is it true that QTouch library was designed only to work with such MCUs? Can I use it with, for example, 'old' ATmega48? Is ...