Capacitance is the ability of a body to store an electrical charge
0
votes
1answer
120 views
Capacitors and capacitance
this time I'd like to ask a few questions about capacitors, all noob questions again;
What's a better idea, having one capacitor at 5x farads or five capacitors at x farads each? I want to get a ...
1
vote
1answer
61 views
Values of capacitors [duplicate]
I'm sorry if this has been asked, as it's a simple question, but I haven't found it.
Is there any reason why capacitors are built in so fixed values? For any other components the manufactured value ...
1
vote
1answer
99 views
how to select capacitor values
I am trying to find information on formulas used to calculate capacitance required for a given circuit. Not a circuit in particular, just in general how to figure out what value should be used. I know ...
0
votes
3answers
67 views
Microphones disturbed by capacitance
I've used several KE 4-211-2 Sennheiser microphones to assemble a device for acoustic signal analysis. They are connected to a National Instruments data acquisition device with ~1 m long cable and ...
1
vote
2answers
153 views
How to measure capacitance without LC meter?
I would like to use capacitors salvaged from old electronics, but I currently don't have a LC meter.
What would be some really simple circuits, that would convert capacitance to something I can ...
6
votes
1answer
151 views
How do I decide what capacitor to use in a circuit?
I am using a voltage regulator and to get cleaner power, the datasheet recommends using a 0.33uF capacitor. However, it doesn't say what type it wants. Stupidly, I ...
2
votes
0answers
190 views
Arduino - Trigger an iPhone's touch screen with no human interaction
I'm trying to replicate part of this experiment. Specifically, I want to touch the screen with a cable and some aluminum foil whenever I send a signal from an Arduino pin. From the blog post linked ...
-3
votes
1answer
102 views
Calculate Potential Difference for capacitor [closed]
I have a simple circuit that controls a 5vdc power source. My question is; how do I know what the Potential Difference is? In the circuit below I am sending 5v DC to a component (dotted box is where ...
1
vote
2answers
116 views
What happens to the circuit Voltage, Energy?
I was recently asked this question to calculate the voltage across a capacitor. The problem is described as follows :-
Consider a capacitor "C" connected across a voltage source "V". Once the ...
4
votes
1answer
243 views
measuring low-value capacitors with Arduino/Atmel
I recently bought a kit at Sparkfun to measure capacitors. (Which is actually this.)
It works well and accurately measures very tiny capacitors, but the firmware is not open source and I would like to ...
2
votes
2answers
167 views
I2C Capacitance
I'm using an I2C interface for my e-compass and controller. The capacitance of the e-compass I2C pin is 20pF, and that of the I2C controller is approximately 40pF.
But the problem is: I want to use a ...
0
votes
1answer
112 views
calculating inductance formula
what is the formula for caculating inductance on the basis of
1)No of turns.
2)Diameter of the wire
3)Diameter of the wounded circle. ?
how to calculate the capacitance value in ceramic capacitor ...
4
votes
1answer
137 views
Proposal for building Low-Current 220VAC Current Detector
I have been reading many such articles and have found no way to simply detect flow through a mains wire at low current.
At .27A for one LightBulb, I was calculating .05mA out of commercial 1:2000 ...
5
votes
3answers
417 views
Calculating Capacitor Discharge Time
I am constructing a system in a solar car, and need to have capaitors large enough to power the Telemetry system for about 15s after power down.
I need to use capacitors instead of the batteries, due ...
3
votes
1answer
125 views
Matching IC drive capacitance with MOSFET input capacitance?
A quick and simple question:
If I have a microcontroller pin that says that it "is designed to drive capacitive loads of up to 70 pF", does that mean that I can directly drive MOSFETs from the pin ...
7
votes
1answer
167 views
Inductive vs. capacitive PCB layout
I've noticed that some high-speed switching PCB's (i.e. microwave) use a layout, where each net is maximized and the 'traces' are the non-copper. Is this to decrease capacitive reactance in the ...
1
vote
1answer
58 views
Capacitive pen input sensors on screen edge
I've got a couple Kobo Touch devices in my possession. I've recently started hacking on the software. I'd love to enable stylus input by putting a Wacom or similar tablet behind the screen, but I ...
0
votes
2answers
85 views
For gates of same drivestrength, what does gate delay depend on and how?
I was wondering what the effect of input capacitance or fan-in is on gate delay.
Also, does anyone know of a relation that links gate delay with different circuit parameters (input load (fan-in), ...
0
votes
1answer
103 views
circuit equations derivation problem
I'm trying to derive from scratch the differential equations that characterise Chua's circuit.
Here are the ODEs I obtain from that diagram. Current is positive if conventional current goes + ...
3
votes
6answers
674 views
how a phase delay occurs in capacitors/inductors with visual images
Capacitors provide a phase delay between the current and voltage. Current leads the voltage by 90 degree. I was taught these only with the equations. But I want visual intuition, what happens in the ...
0
votes
2answers
173 views
Mains Power indicator maximum current draw
I am building a circuit like this:
From here.
This got me wondering how much current can I draw from a circuit like this?
The question would seem to be what is the wattage of an capacitor?
Edit:
...
1
vote
1answer
368 views
How do I calculate necessary mosfet turn on/turn off time?
I'm trying to measure capacitance of C1 using this design:
Everything works from 3.3V.
The mosfets is my addition to it - i want to discharge the capacitor after each half-cycle. Everything works ...
2
votes
2answers
84 views
Volatile capacitance values at low frequencies
When I measure the capacitance of two cables I get very volatile values if I go to lower frequencies like 500 Hz. The capacitance is about 50 nF. Why does this happen?
0
votes
1answer
138 views
going from 5volt 1A to equivalent from a 3V CR2 Battery
I have a small camera with wifi that runs off a 3V CR2 battery. I'm trying to run it from line voltage. Could not find any small transformers that go to 3volt 750mA.
I have an Apple transformer for ...
6
votes
1answer
303 views
Mimic human capacitance
In a video at Kickstarter a project called Tapcaps is mimicing human capacitance for triggering touches to a capacitive touch screen (the iPhone). At 0:45 in the video we can see a glimpse of the ...
5
votes
2answers
156 views
What is the meaning of the nominal frequency specified by manufacturers of crystals?
This answer led to the conclusion that it is unclear what the meaning of the frequency listed by crystal manufacturers actually means.
Given this graph on page 79 of this ECS Crystals Application ...
2
votes
2answers
175 views
Capacitors in series
Okay so I'm looking at RF designs and I've come across a couple of designs which need 2p2 caps.
I've seen
C1.C2/C1+C2
being plugged into a function (the tank part of the circuit) which gives a ...
2
votes
0answers
201 views
Formulas for Integral Components
Formulas for Integral Components:
I am looking for "simple" approximative formulas for integral components. In particular for:
A grounded interdigital capacitor (i.e. above a ground plane and with ...
1
vote
1answer
225 views
MOS Capacitance and Performance
I was learning about the advantages and challenges in scaling down MOS transistors. I came across this statement in Wikipedia :
...
7
votes
2answers
772 views
Why does an ideal capacitor give rise to a rectangular cyclic voltammogram (CV)?
Many scientists are interested in developing supercapacitors, which have electrolyte rather than solid dielectric between the charged plates. In the field of electrochemistry, cyclic voltammetry (CV) ...
5
votes
1answer
1k views
How can capacitance values be determined from a cyclic voltammogram?
I am reading an article (Khomenko, Electrochimica Acta 2005, 50, 2499-2506) that investigates the capacitance of carbon-based electrodes for use in supercapacitors. In particular, they use cyclic ...
2
votes
1answer
130 views
Measuring capacitance by using two thresholds
I want to measure capacitance using a microcontroller. As there are various drawbacks in measuring capacitor voltage from 0V, this resource has it right by counting the time capacitor charges from one ...
6
votes
2answers
264 views
How often should I have to set oscilloscope probe's capacitance?
I got a new Owon SDS7102 oscilloscope and I'm using the included oscilloscope probes with it.
The manual says that the proper calibration procedure is to let the oscilloscope work at constant ...
4
votes
2answers
716 views
I2C extender or repeater?
I am developing a dolly-pan-tilt system, where an Arduino is connected via I2C to three independent rotary encoders for positioning. Having read a few posts on this site and elsewhere, I am aware that ...
2
votes
3answers
355 views
Importance of dielectric in a capacitor
We all know that if we put a dielectric inside, the voltage lowers and capacitance increases. Yet, it lowers the energy density. If capacitance increases, then more charge is stored and so its like ...
2
votes
2answers
215 views
In general, why do capacitors have a higher tolerance than resistors?
In general, why do capacitors have a higher tolerance than resistors? Capacitors have a tolerance of around 10%-40% while resistors have smaller tolerances generally. Why is that?
2
votes
2answers
198 views
What loading capacitor do I use for my crystal?
I am using this crystal (the 7.3728 MHz variant).
The datasheet specifies a 5pF to 55pF load capacitance; is this really so? I was under the impression that most quartz crystals had an optimal ...
3
votes
1answer
233 views
How to make an entire (irregular) surface sense touch with a capacitive sensor?
I'm looking for a way to make a surface touch sensitive. The sensors have to interface with a keyboard encoder to send signals to the computer as keypresses. This is just the way it has to operate. I ...
5
votes
1answer
155 views
Unwanted capacitance in measurement setup - what to consider?
I have a current measurement setup (which supposed to measure < 1nA). It has 20 channels and switched using a relay matrix.
Using a LCR meter I measured for one channel (In the schematic below, ...
4
votes
2answers
408 views
How to measure/compensate wire's stray capacitance
How should one measure and compensate (If necessary) a wire's stray capacitance in low-level measurements?
Is Guarding applicable here? If so, does it mean having a wire with same signal voltage ...
4
votes
2answers
476 views
Load capacitance for RTC Crystal
I'm working with an LPC2387 (datasheet), and pp. 55-56 of the datasheet specifies several options for the RTC crystal with different load capacitance: 11pf, 13pf, and 15pf. For each of these crystals, ...
2
votes
2answers
704 views
Effect of parasitic capacitance on an ideal signal?
How does parasitic capacitance affect an ideal signal?
Ie. We have an ideal signal shown below, what would it look like with parasitic capacitance accounted for?
4
votes
2answers
867 views
Reading very low capacitances with Arduino
I'm trying to measure the capacitance of a very low capacitance sensor (two parallel plates across a block of foam). This is a self-produced force sensor; I'm trying to eventually use some of the work ...
3
votes
5answers
2k views
Why does the distance between the plates of a capacitor affect its capacitance?
Why does the capacitance of a capacitor increase when its plates are closer in distance to each other?
3
votes
1answer
149 views
Diffusion capacitance approximation for bipolar power transistor
I'm trying to remember the approximation for the value of the diffusion capacitance for a bipolar power transistor. I think it might have been gm/Ft? Can anyone confirm this and/or give a reference? ...
10
votes
1answer
1k views
How does a Theremin “antenna” work?
I always assumed that the shape of the antennas was important; a vertical monopole for pitch and a horizontal loop for volume, thinking that this minimized their interference with each other. But it ...
2
votes
2answers
3k views
Trace-to-plane capacitance?
I'm routing some traces which carry high speed UART at 1.8432 Mbaud. The traces will be routed on the same layer as a power or ground plane (because it's a 2-layer design.) This will introduce ...
18
votes
8answers
778 views
Is there a dual of the transformer?
Capacitors and inductors are duals of each other.
A transformer is made of two inductors, and transfers power through mutual inductance, through the magnetic near-field (right?) Also, you can vary ...
3
votes
2answers
458 views
How do I choose the correct capacitors to use with my Crystal?
I am looking at using this crystal for a new circuit design. It will provide the main oscillator for my PIC application.
Here is the part on digikey: ...
7
votes
3answers
392 views
µ in the Middle of a Capacitor Rating
I'm looking at an electrolytic capacitor (and old blue, Philips one used in electronics classes) and am wondering why it is printed with 4ยต7-M.
I tried Googling, figuring that it was a common enough ...
