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# Questions tagged [calculation]

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### How to calculate length needed for heating element (2mm Nickeline/Nichrome wire) to a specified power?

to start off, i dont really understand about electrical engineering. im a mechanical engineering student tasked to continue the project. i dont really understand electrical stuff beside the very basic ...
462 views

### How do you calculate electrical active (3-phase) power with L1,L2,L3 (I) angles to L1 (U) and L1,L2,L3 (I) and L1,L2,L3-N (U) measurement?

I get from a Landis+Ggyr E650 electricity meter data via a serial IR head (62056-21 / D0) about every 20s. This meter provides a lot of data, but not the current actual active power (kW). Some of the ...
75 views

### Issues with getting UR

I'm trying to get UR5 from this schema, but something is not right. All I have so far
720 views

### Energy calculation using Arduino

How I can calculate accurate energy if I have power, current and voltage values? This is the code of energy calculation, the result's it's wrong so how I can fix that? I want to measure apparent ...
325 views

### Calculate power dissipation of split-supply op amp for sinusoidal input

I want to calculate the total supply current and power dissipation of an op amp in a non-inverting voltage follower configuration with a split supply: simulate this circuit – Schematic created ...
204 views

### Flyback converter input current

I have solved A and B of this question but i have no idea how to solve C. any help would be apriciated
207 views

### How to get power consumption from datasheet

I am using this stepper motor on my project and am trying to pick a power supply that will be able to supply enough current to all of my components. Looking at the datasheet I'm not sure whether to ...
1 vote
99 views

### Need help on resistor calculation

I'm currently work through an application note from Texas Instruments about building a programmable power supply. The base concept is fine and I understand it, now I'm trying to go through the ...
173 views

### How do I calculate an incomplete sinusoidal signal's average value and RMS value?

I couldn't be sure because there are parts with size 0 in the signal.
1 vote
71 views

### V=4VDC, R=150ohm, I=9mA, but this is not what I expect, what am I missing? [duplicate]

I have a simple Christmas light LED pack. It features 3xAAA battery compartment, an on off switch, a 10 ohm resistor in series and 9 white LEDs wired in parallel along about an 80cm two wire lead. ...
111 views

### Heat sink thermal resistance

Is there any way to figure out the thermal resistance of a heat sink without using a datasheet or using it in an actual circuit? I mean, simply by knowing its dimensions and material.
53 views

### Sanity check inductor calculation

Input: 3.3 V Output: 13 V Output current: 200 mA (actually less then 60 mA but with some headroom) Ambient temp: max 70°C Regulator: LMR62421XSDE/NOPB So my question: What is the smallest inductor I ...
1 vote
124 views

### Replace LED on PCB with multiple smaller LEDs

I have a small amplifier with a bright blue LED (dome-shaped with a height of 6mm and a diameter of 3mm). I am building a new case and I want to replace the LED with (three) smaller ones, preferably ...
58 views

### Calculation of Power consumption of opamp with positive and negative voltage

I used a single power supply for an op-amp, and I could see the current draw on the power supply. It was easy to determine power consumption using P = V * I. How about dual power supply (+-9V); to ...
1 vote
152 views

### How to calculate RC filter time constant of parallel battery cell filters

I am working on cell balancing circuit for a stack of LiIon cells. The filters are used in front of and ADC input to filter the cell voltage. The datasheet claims that with given values the cutoff ...
810 views

### Loop filter bandwidth calculation

I am trying to Design a PLL using ADF4106 and VCXO. The reference frequency is 10MHz and VCXO output is 40MHz. I need to design a Loop filter for converting charge-pump voltage from PLL into Control ...
612 views

### Calculating Vin/Vout of this circuit

I am trying to calculate the Vin/Vout of this circuit: I did like this: The '+' input from the amplifier is $V_{in} + 2.5V$, and then the resistor divider $V_{out} = (V_{in} + 2.5V) \times 0.1$...
110 views

### Dual state variable filter HP24 output

So I've been playing with 4-stage state variable filter (SVF hereinafter) to get a voltage-controlled filter with Highpass 24db/octave (HP24), LP24 and BP12 outputs. Unfortunately, reading about these ...
359 views

### Calculation for Resistor in Phototransistor Emitter

I decided to ask here for help, I am still new at electronics, I have been trying to figure out the definitions and graphs of this phototransistor, the PT1302 (datasheet here), my doubt is how can I ...
784 views

### How to calculate mAh draw from a battery?

I'm trying to calculate the "drained" capacity from the battery each second so I can get the nearest possible capacity used. This is how I'm getting this. dischargingCurrentSum - Is the sum ...
94 views

### Sizing Circuit breaker, and I believe my calculation is wrong. Can anyone help me out

I am looking at a 3Amp rated circuit breaker, and the datasheet given below of the derating factor, and trip time in second. The average office temperature is 71F. Cable Current rating = Rated ...
502 views

### Total voltage error at the output of the Op-Amp

I have this circuit (shown below), I need to calculate the total error voltage at the output of the Op-Amp due to R3 and Vos. U1 is the LM741, which has Vos = 5mV and ib = 80nA. Till now I’ve ...
134 views

After web researches and a first discussion about general comprehension, I am a bit lost with the load frequency calculation: I see a design which uses two 33pF external capacitors (C1 and C2),with a ...
316 views

### Meaning of Input Leakage Current vs Shutdown Current and Quiescent Current

I am looking at an IC load switch that has values for Quiescent Current, Shutdown Current, and Leakage Current. My understanding is that Quiescent Current is current drawn by the IC in the "on&...
271 views

### Relationship between plating thickness, surface area, and ampere-hours

I am reading a PDF titled Electrochemistry for the Electronics Industry. I am having a hard time understanding the relationship between metals and the Ah (ampere-hour) relationship. For the ...
266 views

### How do I calculate the discharge time of a battery with a step-down converter?

I'm building a battery to drive a small 12V motor which is rated to draw max 7A. The battery has the following stats: Nominal voltage: 14.4V Capacity: 20.4Ah So I calculated that the energy should ...
5k 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 ...
1 vote
230 views

### How do we calculate the charging time of a Li-ion battery if we used a fast charger?

Consider a rechargeable 7.4 V, 5000 mAh Li-ion battery. If we were to fast charge this battery, what would be the charging time? Although it is known that the general equation for charging time is: ...
102 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 ...
1 vote
154 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 ...
1 vote
192 views

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'...
99 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 ...
1 vote
118 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 ...
54 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.
1k 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 = ...
393 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 ...
187 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):...
305 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?
1 vote
107 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 ...
276 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 ...
222 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, ...
1 vote
44 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, ...
761 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 ...
73 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 ...
1 vote
79 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'...
238 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
1 vote
296 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\...
1k 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 ...