Questions tagged [calculation]

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What is the current industry practice regarding the impact of current-limiting fuses on arc flash calculations?

Suppose you have a panel. The arc flash incident energy for this panel is computed based largely on the available short-circuit current (SCCA) to the panel, and the protective devices upstream of the ...
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1k 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 ...
• 2,053
62 views

Estimating junction temperature

I made a measurement using thermocouple to measure the case temperature of my TO-220 linear regulator (L7809). I'll be using degrees celsius for all temperature units and degree Celsius/Watt for all ...
• 401
1 vote
41 views

Trying to figure out rise/fall times for different load conditions

I have a device that requires a certain rise/fall time for its input clock. It specs a .7ns rise and fall time with a 20% to 80% measurement at a Cin=6pf. I should note that the spec rise/fall time ...
• 217
1 vote
39 views

How to calculate values for current and voltage limiting resistors in variable power supply?

I have an assignment, where I have to calculate the values for a current limiting resistor (R3) and a voltage limiting resistor (R14) for a variable power supply. The input voltage to the circuit is ...
• 11
1 vote
87 views

Parallel resistors circuit: remove random resistors and from the total resistance know which were removed

This is more of a mathematics question than an electronics one. With this circuit, I want to know the state of the switches above the resistors, without looking at them. The use case is that I have a ...
• 111
1 vote
101 views

Differential amplifier, calculation of differential and common gain

Maybe someone can help and knows how to calculate the differential gain and common-mode gain in a differential amplifier. Will the formula for differential gain be Ad=Rc/2Re, i.e. in my case 50/40=1....
1 vote
109 views

Determine derivative time of real PID controller

I need help determining the derivative time of a real PID controller. Above me is an ideal PID controller. In my case I have another resistor (let us say R0) before R1 and Cd serial. How do I now get ...
1 vote
52 views

Getting Discharge Safety from a Battery

I would like to calculate the battery runtime for an ESP32, using a 18650 battery with 2600 mAh (Datasheet). When I am using a calculator such as this one, it requires me to put in a discharge safety ...
1 vote
496 views

Calculating steady-state temperature for electrically heated wire

I am working on a program aimed at finding optimal parameters (voltages and feed rates) for a hot wire foam cutter. One starting problem that has to be solved before even attempting to evaluate heat ...
1 vote
64 views

Can the secondary voltage of this old transformer be derived?

Images are of an unknown "4808" PCB-mounted transformer. It has an open 240 VAC primary. Data: EI48 core, around 12-15VA. The center-tapped secondary is 15Ω-CT-15Ω and 1.6H-CT-1.6H according ...
• 16.3k
1 vote
190 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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1 vote
177 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 ...
• 11
1 vote
51 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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1 vote
496 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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1 vote
831 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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41 views

Achieved SNR is different than the simulation results

I have designed a transimpedance amplifier as follows: Based on the simulation, I should get around 58 dB for SNR @3MHz: But what I achieved in my experimental results is as follows: Supply voltage ...
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29 views

How to predict the efficiency of a very low speed Railgun Actuator/Lorentz Force Actuator?

Well, I read somewhere that the slower the railgun is, the higher its efficiency, so I started trying to find out what would be the efficiency of a railgun actuator to move a heavy object (3000kg) at ...
• 360
57 views

How to calculate the time constant for an attenuation of specific frequencies in a Lock-in Amp?

I am new to the signal processing field, so I am studying what I can and trying to figure stuff out, but I have found one piece of information I really cannot find mentioned anywhere, yet seems very ...
28 views

Six LED Strips 24 V with battery - runtime?

I bought six 250 cm long addressable 24 V LED flexible tubes from Sunliteleds.com According to the producer it uses 28.8 W/m 2.5 meters x 28.8 W = 72 W / Strip So if I use a battery with 10.4 Ah at 24 ...
49 views

How can I calculate the right capacitance value if I have voltage, current, watts and power factor?

I have test results. As we can see, there is a lot of information about voltage, current, watts, capacitance, etc. I have tried to calculate the capacitance value (Cap./Ind.) in the picture, but I ...
107 views

What would be the AWG (American Wire Gauge) standard for my wire 1 x 0.75 rm?

I have been trying to figure out my wire gauge standard in AWG format. I bought a coil (100 meters) of wire and the info written on the package is: 1 x 0.75 rm. I understand the 1 in here represents ...
36 views

Calculation of Power Transformers

I'm calculating transformers very roughly, with some approximate equations that I found on the internet, they are working perfectly but I'm supposing that they are oversized... They are power ...
49 views

How to find the right specification of LED corresponding to an incandescent bulb to replace the latter?

I have a motorcycle and its taillight had an incandescent (filament) bulb. The wiring diagram says it's specification was 18W for 12V supply. Now, I want to use an LED (or several) in its place with ...
150 views

HB100 Doppler sensor calculation

I have a question about the first circuit schematics. I calculated the second circuit's fcutLow and fcutHigh frequencies like this: f2CutHigh = 1/(2 * π * 1M * 100p) = 1.6 kHz f2CutLow = 1/(2 * π * ...
118 views

Op-amp plus diodes: resistors' values calculation

I am tasked with following: R1, R3 and R3 are to be calculated so that the diodes work in forward bias. Assuming the diodes have a voltage drop of 0.7 V and the op-amp is ideal I have calculated that ...
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123 views

Pull up / pull down resistor value

Wanting to calculate the value of the pull down resistor for a 555 trigger. For the formula should I use the typical or max trigger current (typ = 0.5 Max = 0.9 μA). I want the calculated value not an ...
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402 views

I made a darlington transistor in LTspice. But, that has different values from theoretical values

As you may see from title, I made a darlington transistor like this. I set each transistor(Q1 and Q2) to have β = 150. So, total darlington β must have 22500 or thereabouts according to a formula ...
574 views

Calculation of capacitor of deep trench DRAM

If I know the depth of the trench L, the size of the DRAM node D and the thickness of oxide (say HfO2) T. How can I calculate the capacitor of a trench?
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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 ...
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59 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 ...
84 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 ...
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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 ...
461 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&...
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468 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 ...
133 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 ...
126 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 ...
55 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.
86 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 ...
46 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 ...
112 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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318 views

Formula for inductance with a rectangular non-air core coil

Does anyone have a formula for calculating the inductance for a coil wrapped around a rectangular non-air core? Seems trivial but this is the closest I've come in searching, and it is for air-core ...
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 ...