Questions tagged [calculation]

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2answers
90 views

Convert 15 minute kW readings to a monthly kWh total

I have metering data (kW) in 15 minute intervals that I am trying to get a monthly kWh total for... I simply summed the entire kW range, then multiplied it by hours in the month 745 (total number of ...
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1answer
59 views

How to make sense of the math behind differential opamp

My first question here! So, I'm designing a simple fully differential amplifier. The final target will be to implement a low pass filter (but I'm not there yet). Although all seems perfectly fine in ...
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0answers
33 views

calculation problem: single ended to differential ADC interface

I got a circuit from the provider of my chip. It's the ACD driver of single ended to differential conversion. However, i cannot get the same value as they marked above the wires [ eg. 0.5(Vin-Vcm) and ...
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1answer
43 views

How to calculate the resistor value necessary for the columns 8x8 led matrix?

I am building an 8x8 led matrix using 5mm LEDs (3.2V, 20mA). I connect it to the arduino UNO through the I2C using the GPIO expander MCP23017. The circuit is as follows: A matrix column is made up of ...
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2answers
63 views

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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1answer
56 views

Project circuit current consumption calculation

I'd like to calculate how much my project circuit is drawing for estimating the duration of my battery. My circuit consists of a near-real time sensor which is measuring and sensing some data over ...
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2answers
66 views

How to calculate resistors for a 555 sawtooth with an opamp sink controlling it's frequency

I modified this sawtooth-wave 555 osc and removed the ground at the 4k resistor, replaced it with an inverting opamp. The opamp produces a negative voltage and sinks the current, that previously went ...
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0answers
53 views

How do I solve this? Can someone give an explanation?

I don't understand how to calculate the timings for trigger and reset. The answers are 394.1ms & 11.3s respectively. But I don't know the explanation behind it.
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2answers
37 views

SMD Resistor Power Rating Calculation

I'm extending my question from previously. How to find SMD resistor and capacitor value and correct size I'm doing some calculation and find something confusing below is the calculations: V = 5 R = ...
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3answers
83 views

How do I calculate the real power curve of a PWM resistive load supplied by rectified AC?

When AC is put through a capacitor filtered full wave rectifier, the output voltage is ~1.414 x RMS input voltage for zero load, and nominally equivalent to the RMS voltage when connected to a pure ...
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1answer
69 views

Is my DC-motor strong enough to move this amount of weight?

I’m thinking about building a robot just with some old parts I have. The main thing is the motors. I have 2 DC Motors Specs below. (It’s a MFA975D Series with gear ratio 49:1) Operation range(Voltage):...
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1answer
35 views

Calculate the ampere hour rating of a battery using current over time and voltage over time

I built a battery and measured the current and voltage of the battery over time. Is there a way I can use this information easily to calculate the ampere hour capacity of the battery?
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37 views

DC motor, confusion in specification about Current

So, I am trying to build a little robot mower, and getting all parts. So I recently buyed two DC 12V motors, here is the specs: Now I am trying to calculate how big or which battery should I use, and ...
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1answer
67 views

AC Measurement of a Transistor

I am trying to analyze a transistor circuit. I should find RMS output and input current and voltage. I have made some calculations but I am not sure of whether they are acurate or not. for input RMS ...
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2answers
41 views

Determining line-to-line vs line-to-neutral loads in split-phase panel

I have a split-phase sub-panel, with two 120V legs (red/black) and middle neutral (white). Given Hall-effect current sensor clamps around some combination of red/black/white going into the sub-panel, ...
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1answer
32 views

Heater - how to define power needed taking into account air thermal dissipation

My objective is to heat a liquid inside a bottle. I have a air gap of 2 cm between the bottle and the heating element (resistive layers). The heater and the bottle is surrounded by a bottle insulator, ...
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3answers
710 views

Can I assume that groundings in electrical circuits can be split?

Assume there's a circuit like this: What I'm asking is if I can split the grounding points like this: The reason I want to do it is just for simplicity sake. I don't have an excellent physics ...
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0answers
57 views

how to calculate C for lm7809?

I need to use a LM7809 to reduce 12-14V to 9V , the device is using 40mA at normal state when I search google for application circuit - I got all kind of valus for Cin , Cout. use this datasheet ...
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1answer
58 views

Off Grid Storage Capacitor Calculations

I'm thinking about using a very large home made capacitor as an energy storage device for a light duty off grid application, running some led lights and some 500w loads for a few hours each evening. I'...
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1answer
114 views

Air gap for a coil calculation [closed]

i would a help calculating the necessary air gap for a coil assuming an ideal magnetic material: Cross sectional area of active material = 100 mm2 number of turns= 30 Inductance= 1mH Thanks in advance
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0answers
44 views

Calculating Antenna Directivity Numerically

The equation for peak directivity of an antenna is this (example source) $${D = \frac{1 }{ \displaystyle \frac{1 }{4 \pi} \int_{0}^{2\pi} \int_{0}^{\pi} |F(\theta,\phi)|^2 sin(\theta) \, d\theta d\...
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1answer
62 views

Transistor Series Regulator calculation

I am new to electronics and have a limited knowledge. I tried calculating the values for a series transistor regulator to simulate in Multisim but still could not figure out a way to do this. The two ...
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2answers
77 views

calculating voltage or current for a plain transistor (no resistor)

the short version of my question is this: how do you know what the current through a transistor will be if there are no resistors? I am reading mostly the second edition of the Art of Electronics, ...
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0answers
41 views

Calculation of the resistors values in a voltage divider

I'm working on a circuit where a 3.3v flash memory, which comunicate with SPI protocol, has to be interfaced to an 8-bit PIC microcontroller working at 5v. For the MISO signal there should not be any ...
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1answer
98 views

Calculation of switching transformer at 100kHz

I am not able to desgin transformer for switching frequency 100kHz. It´s easy to desgin usual transformer for 50 Hz. But I´m totaly out when comes to switching transformers. What material should I use?...
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1answer
46 views

Battery life estimation

I have three AA 1,5V@2950mAh Alkaline batteries in series with a discharge rate of 3% per year. My circuit has a 3V3 LDO that will work until 3V6 is reached, so each battery will need to have at least ...
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2answers
418 views

Reverse Polarity Protection Circuit with P MOSFET and Zener

I have been trying to understand the operation of the following polarity protection circuit (Diagram doesn't show the internal body diode of MOSFET): simulate this circuit – Schematic created ...
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2answers
45 views

Minimal information energy conversions [closed]

I am trying to make a generator and before making it, I would need to know how many kWh it generates, in order to make sure it is actually feasible or if I should redesign it. I am just a highschooler ...
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0answers
197 views

Cable tray width selection as per NEC 392

I would like to ask if anyone know what is the meaning of the letter b used in the formula in the table 392.22 National electrical code 2017 article 392, pic (attached)
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2answers
196 views

Capacitor Vrms vs Vpeak Rating in Transformerless Supply

Why is it that when calculating for voltage across the capacitor in transformerless power supply we need to use peak voltage not RMS voltage value. To be clear I am referring to the rating of C1 in ...
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2answers
55 views

Nodal analysis for nonlinear elements

I have this circuit. I'm trying to find the \$I_{3}, U_{3}, P_{3}\$. For the nonlinear element I have this volt-ampere characteristics: \$ I_{3} = 3U_{3}^2 -U_{3}\$. That's what I am doing. Using the ...
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0answers
78 views

Copper Busbar, DC Copper Busbar [duplicate]

How can I calculate the current carrying capacity of a DC copper bus bar with respect to temperature? Bus bar specifications: Copper Busbar Width=40mm Thickness=6mm Ambient Temp5 (C)=4
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0answers
188 views

Comparator with hysteresis calculation

I'm trying to calculate the hysteresis of the comparator using currents but something isn't right. I'd like a little help to find the hysteresis thresholds without the simplified equations. simulate ...