Zener question

[David_AVD]

A bigger picture would be better next time.  lol

So that diagram shows a piezo, zener and resistor all in parallel.  Now you need to explain what you're feeding it with and what you're observing.

EDIT: For symmetrical clamping, that you really want is two zeners in series, with their anodes together.

[tnadys]

I'm guessing that since you are using just one diode it looks like you're getting only half of the peak-to-peak output that you're expecting.  Put two zeners back-to-back and see if you get something more like what you're expecting.

Having just one zener means that it will clamp at about 700mV in one direction and the zener's breakdown in the other.

You also need to factor-in the piezo element's capacitive reactance.  You might plug the equivalent circuit of a piezo into a simulator and put a zener parallel to it and see what happens.  You will notice that the output is different than if you just put an ideal AC voltage source across a zener diode.  (Which would probably fry the zener, by the way.  So don't do that unless you limit the current.)

No, the problem is that the shape of the + side of the signal isn't what I expected. I first noticed it when I added the zener to a half wave rectifier. I keep saying clip, but clamp is maybe a better term for this crowd. I expected the zener to clamp/clip/remove the top of the wave (anything over the 5V breakdown) which would leave obvious marks on the curve. What I am getting is a curve that looks similar but is within the 5V range (down from 30V). One thing I am thinking is that because of the signal is swinging in and out of the breakdown voltage the curve is getting distorted. I thought I read somewhere there were issues with this but I'm not really sure.

I'm pretty new to this so I apologize if this is stupid but isn't the piezo element's capacitive reactance the point of them? I am using it precisely because they are good for studying rectifiers, zeners and filters. It was an easy source of a dirty signal. maybe to easy in hindsight.

The capacitive reactance will contribute to the signal's attenuation when you put a non-trivial load across it. 

I don't know if that alone can account for what you're seeing, however.  If you can find a datasheet for your piezo element then you can get a better idea if that's the case or not.

I have read a lot of papers and data sheets on these things and the only thing I learned was that a complete understanding was beyond my current abilities. The general consensus from the non-PHD level papers is that they are a source of relatively high ac voltage that bears some non-obvious relationship to how hard they are hit. They are like crystal oscillators that you can hit  .  They are usefull for studying other things though, because they are so sloppy.

[tnadys]

A bigger picture would be better next time.  lol

So that diagram shows a piezo, zener and resistor all in parallel.  Now you need to explain what you're feeding it with and what you're observing.

EDIT: For symmetrical clamping, that you really want is two zeners in series, with their anodes together.

it's a piezo? it's the source that is being observed, or rather the zener effect on the piezo is being observed. Taking out the resistor has very little effect on the signal (when connected to a scope) so basically it is a piezo that is being regulated down to 5V by a zener.

[tnadys]

A bigger picture would be better next time.  lol

Sorry, I rushed, because I am frustrated that two components that can only be connected in one way even needs a diagram. Either way, I am about ready to give up. I asked a simple question about the zener effect on an AC signal and no-one seems to know the answer. I'll probably learn more figuring it out myself anyways.

[sleemanj]

Sorry, I rushed, because I am frustrated that two components that can only be connected in one way even needs a diagram.

If fully specifying your problems makes you angry and frustrated, electronics engineering isn't for you.

[David_AVD]

The real issue at play here is that you haven't been able to clearly communicate to others what you're trying to achieve, what you've tried and how you measured/observed the issue(s).

I mean the above in the nicest possible way.   

[tnadys]

Sorry, I rushed, because I am frustrated that two components that can only be connected in one way even needs a diagram.

If fully specifying your problems makes you angry and frustrated, electronics engineering isn't for you.

Been a programmer for a long time so detailed specs aren't new to me, but two pages of restating how two components that can only be connected one way and ending with a diagram is a little much. In fact reversing the diode doesn't even change the answer just the sign. I can understand that maybe the answer is complicated but the question wasn't. The frustration comes from trying to come up with new ways of saying the same thing. I honestly started to wonder if you guys are just messing with me because a forum for EE's shouldn't need a circuit diagram for this question. Then again maybe i'm just really horrible at asking questions and assume to much, either way it has been a big waste of everyone's time

[tnadys]

The real issue at play here is that you haven't been able to clearly communicate to others what you're trying to achieve, what you've tried and how you measured/observed the issue(s).

I mean the above in the nicest possible way.   

Quite possible. I've been a programmer so long that I think of English as my second language.

[AG6QR]

Been a programmer for a long time so detailed specs aren't new to me, but two pages of restating how two components that can only be connected one way and ending with a diagram is a little much.

But look through the thread.  Where did you say it was two components?  Certainly not in your first post, when you could have specified the problem.  Nor in the first response to the posts that first asked for clarification.  And when you finally gave us a diagram, it shows three components, not two.  So are you now telling us your schematic is wrong?

[Tac Eht Xilef]

... but two pages of restating how two components that can only be connected one way and ending with a diagram is a little much.

You were saying?

That is, in fact, the usual way of connecting a zener to a voltage source. Your way isn't uncommon for certain purposes but, absent of any other explanation, is a little unusual...

If you're getting so very frustrated by questions asked in good faith so that you can help us to help you, I'd suggest walking away and coming back to this thread tomorrow.