45 votes
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Why only sine waves?

Because sinusoids have some important mathemtical properties. The first being how they behave under differentiation and integration. $$\frac{d}{dt}\sin(\omega t+\varphi) = \omega\cos(\omega t+\varphi)...
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  • 19.3k
30 votes

Gain margin and Phase Margin Physical Meaning

Gain and phase margin are usually applied to systems that are amplifiers of some sort with negative feedback around them. The more negative feedback, the tighter the system is controlled. However, ...
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25 votes

Why aren't Stepper motors used in closed-loop systems and PID control?

The main point of a stepper motor is that you get discrete steps. However, the cost is larger size and lower efficiency than a continuous motor of the same torque. Stepper motors also have a low ...
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19 votes

Do working electrical engineers in circuit design ever use textbook formulas for rise time, peak time, settling time, etc

These calculations are absolutely used by professional EEs, for some on a daily basis. However, for many this job has been given to simulation software, such as LTSpice, which is also used on a daily ...
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19 votes
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Confusion in PID loop for the case of zero error?

No, e(t) being zero does not imply that u(t) is also zero. It only implies that the output of the "P" process is zero. Remember, the "I" and "D" processes have memory — they depend on the past ...
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  • 165k
19 votes

Why only sine waves?

If we apply a sinusoidal signal into a linear time-invariant system (LTI), the output of that system will also be sinusoidal, of same frequency, but possibly different phase and magnitude. If we apply ...
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  • 351
18 votes
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Why are low-dropout (LDO) voltage regulators unstable?

A LDO is a control loop. And like all control loops, there is always room for instability. So how do you make a control loop stable ? You provide sufficient phase margin (difference in phase from ...
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16 votes
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PID algorithm: how to account for fast input value changes after a long delay

Your problem is called Integral Windup, it's a common control problem. In a non-linear or otherwise bounded region, the controller can't track the setpoint, and the integral increases to a large value....
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  • 7,158
15 votes
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What is noise gain, really? And how is it determined in the general case?

Okay, after a lot more research, I think I've gotten to the bottom of this. Actually I'm certain it's only approaching the bottom, as I've found this topic area quite deep, but I think I've gotten ...
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  • 6,842
14 votes

Why is the frequency complex

Why s is complex in the Laplace Transform: Note first that the Fourier Transform is a correlation (multiply and accumulate) of our time domain signal to every possible frequency. You could describe ...
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14 votes
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How to mount electronics on a vehicle chassis safely

Avoid ceramic capacitors and ceramic components for applications under environmental conditions that include vibrations and shocks. If you can't avoid them, choose components that use materials or ...
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  • 5,631
14 votes

Why only sine waves?

A pure sine wave is an useful test signal because it has a special property, it contains only energy at a single frequency, while other waveforms contain energy on multiple frequencies. So depending ...
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14 votes
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How do power grid systems supply power to new loads coming online?

Where that additional 5MW of power came from instantly until the power system frequency go down and active power governors speed up the generators (obviously there is a time delay)? The voltage on ...
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13 votes

Do working electrical engineers in circuit design ever use textbook formulas for rise time, peak time, settling time, etc

You refer to these basic formulae at first and then find the real world has a lot of non-linear characteristics like XOR phase detectors in a second PLL loop response when you exceed the phase limit ...
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13 votes

Why aren't Stepper motors used in closed-loop systems and PID control?

This is not actually particularly rare. In industrial systems, stepper motors with encoder feedback are relatively common. And for hobbyists, there is e.g. the Mechaduino project. There are several ...
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  • 4,719
13 votes
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Control one relay via multiple 12 V DC signals

Since you need isolation, you will need a relay for each appliance. Even if you didn't strictly need the isolation, it would be recommended since it might be hard to safely share the same voltage (...
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12 votes
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Effect of right half plane zero on bandwidth of control system

As you know, poles and zeroes are the respective roots of the denominator and the numerator of a complex transfer function. Once they are known, they can be placed on a map - the \$s\$-plane - ...
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11 votes
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How to tune a PID controller to a nonlinear process

How to tune a PID controller to a nonlinear process? You don't. You linearize the process, then have the PID controller work on the linear values. By "linearize the process", I don't mean to ...
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11 votes
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over and critically damped systems settling time

TL;DR: NO, you can't use the underdamped settling time formula to find out the settling time of an overdamped system. And you can't use it for a critically damped system either. LONG FORM answer ...
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  • 5,631
11 votes

Why only sine waves?

Only sine wave don’t have harmonics (frequency spectrum at integer multiples of the main periodic frequency), which have energy, and thus can radiate RF above and outside the fundamental frequency. ...
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  • 4,481
11 votes
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how the area is exactly zero?

The dirac-delta function has an area of 1 when integrated. The red area and the delta function have the same area. When integrated from t = (0-) to t -> inf the total area is 0.
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11 votes
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Why is frequency not measured in db in bode's plot?

Frequency is not a measure of signal amplitude or power hence, talking about "this or that" frequency in decibels makes no sense. If somebody says "increase the frequency by 3 dB"; ...
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  • 384k
11 votes

Why is frequency not measured in db in bode's plot?

We could start using dBHz and see how it feels. My guess is it won't make life any simpler or help understanding. NOTE however : logarithmic frequency scale is already in use, and has been for a while ...
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10 votes

Why are low-dropout (LDO) voltage regulators unstable?

"The older high-dropout regulators with N-type transistors didn't seem to have this problem. " The answer is as follows: The npn-type transistor used as a control element is operated in a common-...
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  • 22.6k
10 votes

The term Feed-forward and its meaning?

Feed forward refers to the direction of the signal flow. For feed forward, the direction is, well, forward :-) I think it is easier to show an example. I know that many "sigma-delta" ADCs (analog to ...
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  • 78.8k
10 votes

Confusion regarding control system of a Mars rover

Mars rovers don't move very fast, that is an important part. The "drivers" from Earth plan a rover movement for months, testing out scenarios, studying the topography, etc. Specific movements are ...
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  • 2,508
9 votes

Why is the frequency complex

The Laplace transformastion is an extension/generalization of the Fourier transformation. Because the Fourier integral does not converge for all functions we introduce an additional term \$e^{-\sigma ...
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  • 22.6k
9 votes
Accepted

How do I size the output capacitor for a DC bench power supply?

You seem to have the whole circuit in LTspice anyway. A start-up analysis will tell you most things you want to know. Replace your "big" (45 V) DC source with a source that has a pulse definition, i.e....
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  • 17.8k
9 votes

Could you explain how feedforward is used in walking?

A good example is driving a car around a curve. In a pure feedback system, you go straight until the error signal tells you that you're not in the center of the lane anymore, then adjust the steering ...
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9 votes

How to mount electronics on a vehicle chassis safely

For prototype devices (which should last several months and are OK to fail occasionally), it is usually enough to mount the PCB on rubber inserts instead of bare screws). This greatly reduces peak ...
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