Why my students love me. :)

KL7AJ

Joined Nov 4, 2008
2,225
I long ago banned "multiple guess" questions in my electronics classes. My exams now consist of one-question essays, such as the followiing.

Draw a schematic diagram of a circuit that will generate precisely the waveform shown in Figure 1.

Eric

Wendy

Joined Mar 24, 2008
21,937
My first thought is a tank circuit being pinged by a pulse. What others have you got?

Just for the heck of it, here is the waveform without Word...

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KL7AJ

Joined Nov 4, 2008
2,225
My first thought is a tank circuit being pinged by a pulse. What others have you got?

Just for the heck of it, here is the waveform without Word...

good start....now give us some values.

eric

Wendy

Joined Mar 24, 2008
21,937
24 pulses / ms = 41.7µs period, frequency is 24KHz (resonant freq). As to Q, I'll save it for the other folks, (in other words, not a clue).

steveb

Joined Jul 3, 2008
2,436
I long ago banned "multiple guess" questions in my electronics classes. My exams now consist of one-question essays
When I was a freshman in college, I took the usual introductory Physics class which was a huge lecture hall with > 300 students in two sections. When the final exam came, I and many other students could not make the scheduled final exam because of conflict with athletic competitions. The Professor was very annoyed to have to give a separate exam because he felt that education should come before sports. However, Dean pressure forced him to accomodate us.

The Professor's choice was to give the easiest Physics final exam in history. He asked very basic essay questions and asked for very simple sketches like "show a sketch of kinetic energy versus velocity". There were no calculations or logical thinking needed - just a basic understanding. When I saw the exam I laughed and thought he was showing mercy to us poor stupid jocks, and I passed in my exam for my A grade.

I later found out that most of the people failed the exam. They were so used to just punching numbers in a calculator that they had no real understanding of the Physics. The Professor had his revenge!

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KL7AJ

Joined Nov 4, 2008
2,225
24 pulses / ms = 41.7µs period, frequency is 24KHz (resonant freq). As to Q, I'll save it for the other folks, (in other words, not a clue).
\

For underdamped oscillation:

beenthere

Joined Apr 20, 2004
15,819
Maybe a first attempt at a linear regulated power supply?

thatoneguy

Joined Feb 19, 2009
6,359
Maybe a first attempt at a linear regulated power supply?

I'm glad you are still trying and doing great work KL7AJ!

<begin off topic rant>
Used to do that. Then the dumbing down of America took over and get rules changed to "tests and quizzes cannot ask a question not answered during class". To the point of "The Exact Question". Such as applying 6th Grade History rules with electronics. e.g. "What year was the Declaration of Indepence Signed?". Yes, this was a college level group.

Schools today only want to create students who will obey and repeat, making them think is almost a Criminal Act.

I gave up fighting the system.

</end off topic rant>

peajay

Joined Dec 10, 2005
67
Well, the attached photos are the best I could do. I hope I haven't completely failed. Surely being able to build such a circuit counts for something, even if I can't design one off the top of my head.

In the original image, at the beginning of each 1 ms period, the amplitude of each successive cycle of the 25 kHz signal is about half of the amplitude of the previous cycle, but by the end of the 1 ms period, each successive cycle is nearly the same amplitude as the previous. I haven't a clue how to make both happen at the same time, so in each of the two photos, I tried to meet one of those requirements at the expense of the other.

It also appears my 25 kHz is way off, but I'm not taking any more photos. I'm sure you can trust that I know how to swap capacitors.

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beenthere

Joined Apr 20, 2004
15,819
To be a tad more serious, a pulse excitation of a twin-T filter will ring like that.

SgtWookie

Joined Jul 17, 2007
22,210
Sorta like this...

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