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What result range will the capacitor switch between?


A simple sawtooth wave generator circuit for generating a saw tooth wave form using a NE555 IC is given below. The frequency of the wave form can be varied by using a POT.

The capacitor C, resistor R and zener diode forms a constant current source for charging of the capacitor. When the voltage across capacitor reaches 2/3 Vcc the internal comparator inside 555 goes on and capacitor discharges. When the voltage across the capacitor goes below 1/3 Vcc the internal comparator goes off and now capacitor starts charging. 

So what's the result of the capacitor ? What result range will  the capacitor  switch between?



Edited by Jane123

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It sounds like your instructor has given you a wonderful problem.  Please pass on to him/her that I like the problem.  It also sounds like a good one to learn from.

That said, let's turn to your question and take a look at it. 

The first problem is that you just copied the problem verbatim into this forum.  You are citing parts and pieces by abbreviated number so that ... I'm not certain what parts and pieces you are citing.  I think you'd have a better chance asking someone from your class, whether instructor, students, or graduated students, for help than you would get asking here.  For example, what is a 555? Whose part is it?  What manufacturer are you talking about that has a part number 555?  Sure, you list a web page for the NE555, but that web page lists parts from Texas Instruments, SGS, UTC, ST Microelectronicss, and more.  Your instructor as well as other students from your class would know this answer.

The second problem is that you mentioned a circuit "given below".  This is how problems are often worded in tests, exams, homework problems, etc.  The instructor then draws a picture of the example circuit, and asks you to evaluate it somehow.  That's really good for learning, and I would suggest you try it.  Real-life problems are rarely so clear cut--sure, you'll have a circuit to work from, but it is never "given below"--often times it is somewhere in your notes from when you built it, or located within someone else's schematic diagram.  On this forum, however, your "given below" line with no circuit "given below" identifies you as 1) a student, 2) one who either doesn't understand the language the problem was written well enough to know the circuit that was "given below" would need to be duplicated on a forum, or who doesn't really think it is important, or perhaps one who thinks all EE classes use the same problem sets worldwide, or perhaps just one who cut, copied and pasted the problem onto the web.  In all of these cases, I would recommend you take a bit longer to understand the problem yourself, before trying to ask someone else for help.  Indeed, I would highly recommend that you try solving the problem yourself before you ask for help.  This is how people learn.

The third problem you have is your choice of forum.  This forum is specifically put together and designed to help people who are trying to use Digilent products.  It is not a general engineering forum.  You may, or may not, find someone willing to speak up enough to give you an answer to your question here--but I doubt that the paid Digilent staff who work this forum will pick this up--it's just not something they are paid to do.

May I recommend to you that you try working your problem yourself first, and then if you get stuck that you ask someone from your school, your class, or even better your instructor?  They should be in a much better position to help you than I would be.

Good luck!


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