Math or Mathematics is the abstract study of topics such as quantity (numbers), structure, space, and change.
0
votes
2answers
70 views
Average Power Formulas
I've becomes a bit confused with the average power formulas. These formulas can be found on Wikipedia here and here. Let's suppose V(t) = 1V (DC) and we have a square wave for the current that ...
4
votes
2answers
78 views
Salvage data from a reverse connected thermocouple?
My SAE Baja team had a competition this past weekend, and we were using some thermocouples in order to get some temperature data on the drivetrain and engine.
They were hooked up right before the ...
1
vote
1answer
117 views
What is the physical meaning of an LC circuit having a negative transfer function?
Say you have an ideal LC circuit:
simulate this circuit – Schematic created using CircuitLab
The transfer function of this circuit is a complex voltage divider: $$ \frac{\frac{1}{sC}}{sL ...
2
votes
1answer
95 views
Converting raw temperature data to Celcius L3GD20
I have an L3GD20, which is an accelerometer with a temperature sensor built in, and I want to make sure my math isn't funky regarding the temperature. I'm not exactly experienced with embedded ...
4
votes
1answer
113 views
Need help interpreting a basic circuit question
In my Nilsson "Electric Circuits, 5th ed" book, there's this drill exercise near the beginning of the book.
Here it is:
Current at the terminals of the element is
t<0:
$$
i=0
$$
t>=0:
...
1
vote
3answers
153 views
Attempting to determine power consumption
So I am attempting to determine if the battery I choose can power the devices I need. This is my first day doing anything with ohms and current and such. So go easy.
I have:
2000mAh battery
45mA ...
2
votes
2answers
240 views
Overflow detection in a CSA (Carry-save Adder)
How do you detect overflow when you have a CSA?
I have 3 16-bit two's complement inputs and a 16-bit output and I'm wondering how do I detect overflow?
0
votes
0answers
63 views
JFET “How to find resistance of the device”
I have this homework question that I can find one way to get the answer but I want to use a certain equation "attached" to find the answer also. I'm having a hard time understanding what to ...
2
votes
1answer
49 views
How does one compute the ripple currents seen by an active PFC output capacitor?
Suppose one is designing a single-phase power-factor-corrected power supply, with a known average current load:
The ripple current seen by the output capacitor is critical. If that current is too ...
0
votes
1answer
106 views
Find the peak load of a power plant for the given load equation
The daily load demand of a grid is given by
$$P=P_{max} \cdot cos(\pi t/24)$$
Here \$-12hrs ≤ t ≤ 12hrs\$. Maximum power occurs at (\$t=0\$) and minimum occurs at (\$t= ±12\$). A \$10 GW\$ hydro ...
1
vote
2answers
307 views
Double-Subscript Notation for Voltages
I have read from some book that: "The voltage quantity symbol V sometimes has subscripts to designate the two points to which the voltage corresponds. If the letter a designates one point and b the ...
3
votes
4answers
209 views
Component with an impedance that has a negative real part
Is there an electrical component such that its impedance has a negative real part ?
Fact: Any electrical component made from resistors, inductances, capacitors (connected in possibly complex ways ...
1
vote
2answers
134 views
ARM Power/Exponential Function
I'm trying to code an exponential function for use on a PWM signal.
My question is, does anyone know how to do a power function on an ARM cortex-M (STM32F4 in this case, which has an FPU) ...
0
votes
2answers
229 views
basic math question about voltage, ohms, resistance
total n00b here. After working on several projects by copy & paste from other people's schematics and code, I'm finally digging in and learning some of the math to know what I'm doing.
If I have ...
3
votes
1answer
101 views
Convert between dBA, dBV and RMS values
How do I convert between dBA, dBV and RMS values? For example, I have used a current probe (clamp) with a gain of 100mV = 1A to measure a series of currents in dB and I would like to know the ...
4
votes
2answers
3k views
how to select capacitor values
I am trying to find information on formulas used to calculate capacitance required for a given circuit. Not a circuit in particular, just in general how to figure out what value should be used. I know ...
2
votes
2answers
537 views
I have to determine if the signal is linear, time-invariant, and/or causal
Here is my problem:
$$\frac{d^2y}{dt^2} + 5\frac{dy}{dt} + 8y(t) = \frac{dx}{dt} + 3x(t)$$
I have to prove if this system is homogeneous and additive in order for the function to be linear, but can ...
-1
votes
1answer
126 views
what type of electronics job would combine mathematics, electronic design and programming into one [closed]
There are quite a few different areas of jobs in the Electronics industry.
We have Analogue, Digital, Embedded, Telecommunications, Control and much more. What I wish to know is that what job would ...
3
votes
1answer
432 views
Constant current source math - Using AD8276 differential Op-Amp
So I'm trying to implement a constant current source to conduct a specific measurement using a
AD8276 differential amplifier. I'm trying got derive the equations my self for sanity check, and to give ...
4
votes
3answers
257 views
Solving this op-amp circuit
I would appreciate some help solving the following circuit. I've been trying for a very long time and can't get the same answer the book has. I'm trying to get \$ V_o \$ in terms of \$ I_{os} \$.
...
3
votes
1answer
144 views
Switches needed in an n-location multiway switching system
Wikipedia shows us we can construct a two location multiway switching system with two 3-way switches:
They also teach us how to perform three location multiway switching with two 3-way switches and ...
1
vote
2answers
140 views
Basic circuit analysis - diferential equation
This is the circuit I got from an example in a book "Practical Electronics for Inventors", on page 48:
How can one understand that \$0=R\frac{dI}{dt}+\frac{1}{C}I\$ implies ...
1
vote
1answer
424 views
How does one compute the ripple currents seen by a boost converter output capacitor?
Suppose one is designing a boost converter, with a known maximum current load, and a known inductance:
The ripple current seen by the output capacitor is critical. If that current is too high, the ...
4
votes
1answer
726 views
How does one compute the ripple currents seen by a rectifier filter capacitor?
Suppose one is designing a full-wave rectifier bridge, with a known maximum current load, and a known input inductance. Assume three-phase for this example, though the same concept applies to ...
2
votes
3answers
231 views
Does LTSpice support a “Remainder” or “Modulus” function?
I am trying to change a parameter in LT Spice with if statements and make it change on whether a different value is even or odd.
Mathematically, this would be easy with a remainder or modulous ...
1
vote
0answers
55 views
Are descriptor systems necessarily non-minimal?
I am working with model order reduction for electrical circuits. I am looking to implement Balanced Truncation as a form of model reduction.
The systems I work with are definitely stable, but not ...
3
votes
2answers
219 views
How to mathematically determine the frequency of a tone based on components being used
My REAL question is how to choose the right components if you want a specific frequency spit out from a 555. In my particular case I want a potentiometer to control an output frequency from 16Hz to ...
3
votes
1answer
207 views
Addition and subtraction in digital electronics
Why is it that addition of the 2's complement is an efficient method of subtracting? Does this simplify the circuit?
6
votes
4answers
1k views
How fast does a 64-bit multiply or divide execute on an FPGA?
When using a regular FPGA such as Xilinx Spartan 3 or Virtex 5, how many cycles does a double-precision floating-point 64-bit multiplication or division take to execute?
As far as I understand, the ...
-2
votes
1answer
135 views
SQNR of 16 bit signed multiplication with MSB storing in 16 bits
I'm trying to figure out what the SQNR is if I multiply 2 16-bit signed integer values and store the result as a 16-bit signed integer, dropping the least significant bits.
For example:
a (16 bit ...
0
votes
1answer
99 views
Calculating run time for a device with variable current draw
I recently built a small microcontroller-based project for a friend that consumed different amounts of current at different times. I wanted to calculate the run time for a given battery type (but ...
1
vote
3answers
290 views
Can you sum and difference in a single op-amp?
I want to take two independent differential signals (audio line inputs with unknown properties which may be present or not), remove any common-mode noise from each of them (they could each have ...
-1
votes
1answer
90 views
Math: Temperature tranform equation [closed]
While reading the MAX6605 datasheet, which is an analog temperature sensor, I ran across the following:
The temperature-to-voltage transfer function has an approximately linear positive slope and ...
2
votes
1answer
179 views
What “rule of thumb” to use for mapping -3dB frequency to ideal response for 2nd order Sallen-Key?
For a first order passive filter (RC circuit), we often reach for a the familiar 10X rule. If the -3dB corner frequency is f, then "ideal" frequency response starts at 10f.
What similar factor can be ...
1
vote
1answer
416 views
Calculating dBFs from RSSI
I have RSSI calculated as vector magnitude.
$$
RSSI = \sqrt{I^{2}+Q^{2}}
$$
I and Q are 12bit values from ADC. Is there a way to convert RSSI to dBFs and how it is done?
3
votes
4answers
295 views
Why am I not arriving to non-inverting amplifier equation?
I was trying to derive the non-inverting amplifier equation and I ran into some trouble deriving it.
By making the voltage between R1 and R2 VRef, I set my equation to
Vin - VRef = Vout.
Because
...
11
votes
5answers
716 views
Advanced Math in day to day Electronics? [closed]
So i've been watching the MIT 6.002x Classes and they are really interesting, I feel like i've got a good grasp of Circuits and the Basics (I graduated with a CS degree...but EE appeals to me too).
...
10
votes
3answers
2k views
Why V rms instead of V average?
I'm looking at an equation for average power in a signal
$$
p_{avg} = \frac{1}{R} v_{rms}^2
$$
and wondering why it isn't
$$
p_{avg} = \frac{1}{R} |v|_{avg}^2
$$
1
vote
2answers
213 views
Block Diagrams with offset in control theory
I have an equation in the form $$y = mx+b$$. In block diagram form, I could draw this with a proportional gain block and a summer. I was wondering if there are some clever tricks where I can make ...
6
votes
3answers
133 views
Is there a function to model the resistance between 2 metal probes
I'm trying to design something that will measure the amount of rainfall in a small container. And I was wondering if there was a function I could use to calculate the resistance of the metal probes ...
7
votes
1answer
405 views
Constant power discharge of a non-ideal capacitor
My employer sells boost converters to hold up motor drives during power loss. These boost converters are fed from capacitor banks. In order to size these banks correctly, we need to take their ...
4
votes
1answer
579 views
Why does the base-emitter voltage of a BJT decrease with temperature?
According to Sedra/Smith Microelectronic Circuits, \$v_{BE}\$ changes by \$-2\text{mV}/\text{°C}\$. I cannot understand how this could possibly be the case given the equations I am familiar with.
...
5
votes
5answers
356 views
Calculating resistance in decibel
In EMC there is an equation for charactristic impedance (If I am not wrong) that is defined as:
$$Z_w = \frac{E}{H}$$
As you know \$E\$ is expressed in Volts and \$H\$ as Ampers.
I had the exam ...
1
vote
2answers
195 views
How can I determine the peak power consumption of my office
how can I determine the theoretical peak power cost per hour for my computer? What is the formula I can use to calculate this? Do I need to know amperage?
My current cost per hour is ...
1
vote
2answers
190 views
How can I do a frequency sweep when the frequency modulation index is dependent on the amplitude?
I have a question regarding frequency modulation and the modulation index. I know that the modulation index can be given by
$$\beta = \frac{\Delta \omega}{\omega_m}$$
So the value of the ...
0
votes
2answers
425 views
Is feedback transfer function the same as the transfer function for the whole circuit?
I have a circuit very similar to the inverting band pass filter circuit here:
I was asked a question about the circuit's feedback transfer function. Is this the same as the transfer function for the ...
5
votes
2answers
456 views
transfer function of a full bridge diode rectifier
I'd like to find the s-domain transfer function of a full bridge diode rectifier with capacitive output filter. Surprisingly, there doesn't seem to be much literature on this.
Analytically, I am ...
2
votes
4answers
423 views
How to fix rounding errors on microcontroller?
Here are the specs for the chip/chip family that our vendor is using.
For our product we are asking them to perform a calculation by multiplying a number by a factor that has a decimal point...for ...
-1
votes
1answer
451 views
how to calculate exp(x) [closed]
Could someone explain me how to calculate "exp"?
Basically I have to calculate intrinsic density for silicon at T = 200K
$$n_i=(N_cN_v)^{1/2}exp(-\frac{E_G}{2E_T})[cm^{-3}]$$
$$\sqrt{N_c ...
1
vote
1answer
91 views
Communications engineering, call arrival rate, poisson
I am taking a course in communication engineering which involves some probability theory that I'm not quite familiar with. Please see the attached image for my problem. I don't get why that equation ...
