# Questions tagged [calculation]

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213 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 ...
47 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 ...
33 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, ...
46 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\...
208 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)
34 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 ...
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 ...
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 ...
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 ...
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.
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 ...
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 ...
74 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 ...
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 ...
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 ...