Hello
i am new to qspice and would like to simulate an piezo disk signal into the my small network. How should I simulate such a signal correctly.
I am currectly waiting for a small oscilloscope (120Mhz / 250Msa/s) to analyse the signal that comes out with a hard knoch (pellet from a pellet gun) hitting the piezo disk either directly or in directly.
Kind greats
Matthieu.
You could try something like this. I tried to measure response but it is highly dependent on the measurment setup and the applied force on the piezo disc. In conclusion it is exponential decay of sine wave.
Best regards
piezo.qsch (3.1 KB)
It seems good. Where is your reference to modeling this one? Can you share with us? Thanks. @bordodynov
https://iopscience.iop.org/article/10.7567/JJAPS.22S2.143
I modeled the mechanical action with a control source and a pulse source.
@ All, thank you all for taking the effort to respond, much apprecated.
@Ivan1
Thnk you this looks very useble. I will soon get my small oscilloscope and I will compare this with the output as I will get it from here. But you are definatly right, Iâm expecting an exponential decay of a sine wave. Basically I think I will only be interested in the initial peak. and maybe the OAC over a certain time frame for now.
@bordodynov
You too, thank you very much!
at this moment I am not really sure how to interpret this but it does indeed seem like the integrated (AOC) of the positive and negative voltage in a decay manner, but the shape of it seems a bit perculiar to me but could be very correct for what I need. Just need to understand it better.
So thank you very much! I will definately come back to this after I read and understood the article.
Kind greats
Matthieu
Without a diode limiter, the picture is different - a large voltage surge is obtained. This release may damage the receiving circuit. Youâve come across a piezo burner. What kind of tension do you think is developing in her? Usually, a diode limiter is placed after the piezoelectric element. You can remove the diode limiter from my circuit. I do not know how my simulation quantifies reality. Perhaps the transmission parameter of the dependent current source is significantly less. But beware of damaging the oscilloscope!
Yeah I am very aware of the presence of the Voltage surge.
Thatâs why I am wanting to do some simulations first.
Afterwards I plan to measure with a 100x probe and start with only small âknocksâ
To see the pure signal. But IRL i will indeed use a limiter of some sorts and the knock will be very subtantial. On the otherhand it is just a piezo disk. not an piezo igniter. But all test and steps should be taken with a precaution.
Hello to all,
I have been playing around with qspice and am slowly getting more than hang of tit.
please do take on account that I am completely new to spice programs and generally not very knowledged on electrical network(ing) so this is a challege for me.
@ivan1 and @bordodynov,
looking at both you examples and
reading the article bordodynov posted, plus
what I know to have seen on online scope measurents,
and what physics implies I have been fooling around with qspice and came to the following simulation (for now).
The Resistance and conductance of the piezo disk is measured. The values for the decaying sine signal I have âguessedâ, more real numbers will be measured as soon as I have my oscilloscope.
(and yeah, i will be carefull!, scared to wrack it so⌠will not take much risk. but I believe using my 100x probe will keep me fairly safe. Measuring with my MM will not do much as I believe it will not be fast enough to catch the first sine wave.
The value of the R load is also a temporary guess, but I feel like this is an oke basis to work from for now.
ofcourse i am open to all critique.
@ivan1, I have two specific questions for you concerning your example.
Addition:
playing around a little more I have âaddedâ two diode to "filter uot the negative waves.
as one can see in the added image. Ofcourse this leaves me again with the high voltage issue, which will destroy my wemos board upon connecting. So I tried to add another parralel diode in reversed direction as from @bordodynov diode limiter, which I feel to be a very beautiful way to accomplish this task. but things went abit hicky⌠as one can see, there is some negative voltages sipping through, anythoughts on that?
kind greats
Matthieu
I measured output of a random piezo transducer, like this one:
I made csv file from that picture and ovelayed it onto simulation.
meas2.csv (11.3 KB)
Best regards
I apologize. In my example, I did not correctly give the formula for calculating Rs. You need s=2piFre*l/Qq.
Here is an imitation of a piezo emitter. Apparently, it has an additional low-frequency resonance with low Q-factor. I simulated this with a sinusoidal decreasing signal.
@ivan1
ah that explains a lot, had no clue that that was an overlay from an actual physical measurement.
thank you fro doing and explaining it ! much appreciated.
My intension for the final measurements will be indeed a really good kick. so this p2p voltage is indeed something.
@bordodynov
That is indeed a very interesting simulation! very simular to alex1 his physical measurement.
I will add the diode limiter too it and see what that does
I will now have some experiment with changing the values of Freq, Co, Kc, Qq and see what it does 
Thank you both so much for all your help
Also, I need to go and investigate the workings of the diode limiter.
I believe this clips the signel. but for my needs I will need to keep the spike but the intensity relative to the original voltage spike, to be able to detect the original knock intensity.
Kind greats, Matthieu
After some thinking, I thought of the simple voltage divider. setup, I could use a variable resistor to fine tune it. but i am not sure how it would be heat compensation wise.
anyway, this is my small development, any thoughts / crtitique on this would be much appreciated.
additional, i would like to know how to find out hoe to measure voltage over two specific points.
now i know how to measure between ground and one point. but the second is always ground, how can I do this correctly
kind greats
Matthieu
@ivan1
I would like to ask you a few more questions concerning your test with the disk.
I am fairly new to the use of an oscilloscope, and just got my zeeweeii DSO3D12 today and I donât want to kill it instantly.
@ all:
I found the channel of [ultrasonicadvisors.com] which i will be browsing through the next coming days to see what information specific to my plans i can learn from them.
Also, check this video: https://www.youtube.com/watch?v=hmemnF16wfw
Best regards
@ivan1
Thank you very much for this input again! I will try to get a measurent this evening.
Interesting video too, unfortunately for me is that he is interested in the smallest of vibrations.
I am interested in the specifics of the peak values (and the duration) and maybe even the current, but i doubt that will be enough for me to actually measure.
but never the less interesting, also the part where it is good to couple it to the surface. something I will be dealing with at a later stage of my design.
Found the hit with the hammer very interesting to see though.
Since you inquired about the type of probe and expressed concern that your test could damage your oscilloscope, it is essential that you fully understand how to determine the maximum rating of your measurement equipment.
About Probe
Referring to the oscilloscope parameters of ZeeWeeII DSO3D12, it is specified that the peak voltage with a (10x) probe is +/-400V (but, in general, this specification is typically found in the probe specifications rather than in the scope specifications). The probe that comes with your scope is a x1/x10 switchable probe. This specification means that you physically switch this probe to x10. The x10 button on the oscilloscope panel is only a software configuration that informs the oscilloscope that your probe is set to x10, scaling the voltage axis to provide you with the correct reading. If you only press x10 button on the oscilloscope but still have your probe in x1 setting, you can damage your scope if more than +/-40V according to specification.
About Time Scale
If you gently press and release the piezo disk without a load, it should generate a voltage for approximately 100ms to 500ms. If you are new to using an oscilloscope, you can set your oscilloscope with a timebase of 500ms and a voltage scale of about 5V or 10V per division. Let the scope run, gently press and release the disk, and you should see a profile similar to what @ivan1 mentioned in the YouTube video. With this setup, you can increase the force and observe how your disk performs in real time without worrying about whether the signal is triggered, as your oscilloscope will keep rolling.
What you can expect is that when you press the disk, you will get a positive voltage, and when you release it, you will get a negative voltage. If you tap on the disk, you will observe a voltage that rapidly fluctuates, resembling a combination of the aforementioned actions (pressing and releasing in a very short period of time).
About Current Measure
Regarding current, it can be a very challenging topic with a low-end oscilloscope. Assuming you connect your piezo disk with a x10 probe, and a x10 probe typically has an input impedance of 10Mohms. This means you are effectively loading your piezo disk with a 10Mohm resistor. By using the formula I = V / R, if you assume you get a peak voltage of 40V, the current is approximately 4uA. Depending on what you aim to learn, measuring current in a resistive load condition may not be essential, as you can always predict it using Ohmâs law.
@KSKelvin
Thank you of all your inforamtion, It is much appreciated that you took the time to post that.
I was not aware that a 10x probe would be safe till 400V, Additionally I wasnât sure it the safety part was due to the probe used or that Voltage window had some part in it too. Thats why I tried my 100x probe,which was ofcourge to much attenuation. So no signal was shown.
About measuring the currunt, itâs the intention to measure that also with the wemos board. But I doubt very much that that would be possible, specifically when the amp load is that small. Additionally I am not sure It would give me any inofrmation I can use. that is something i will need to figure out in the future.
Never the less, I learned much from your post, so thank you
Kind greats
Matthieu.
