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Piezo ignitor pulse shape

1) I am wondering whether the piezo ignitor of a BBQ lighter generates a single spark or multiple sparks.

2) In other words, I would like to know the pulse shape of the piezo ignitor, but I haven't got an oscilloscope. Is it AC or DC, is it a single monopolar pulse, or a bipolar pulse, or a dampened oscillation?

Probably the pulse shape depends on its design, so I dissected a piezo ignitor. Please see the image at

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The piezo electric body is apparently composed of some indistinct grey matter in a relatively large brass cup.

3) is the grey matter the piezo ceramic (PZT)? 4) what is the purpose of the relativey large brass mass. Is it just a heavy anvil?
Reply to
Arnold
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Take a look at this page, do a find for PZT on the page. It shows waveforms and Q. Although I don't make any sense of either of those. I think the voltage and the Q is much higher than what it says. physics.mercer.edu/hpage/technique.htm

Mike

Reply to
amdx

..

Thanks for the link, although it seems to discuss damping in PZT in a very different situation than an ignitor. For example, the PZT in figure 17 has a resonance frequency of about 1 Hz. That is not very typical for an ignitor.

Reply to
Arnold

that depends on the spark gap, and the how the mecahnical stuff perfroms....

yes.

piezos work by pushing electrons round when you deform them as they return to their base shape the electrons are pushed back the other way so it'll be bipolar.

little else can be predicted.

yup but not in a precisely predictable way.

the electrical load piezo will have a large effect too, and given that the load includes a spark gap the effect won't be easily predictable.

that or a coating to protect it.

I expect so.

For an indication of the waveform produced by the piezo without the spark gap consider the sound it makes.

Bye. Jasen

Reply to
Jasen Betts

gap

Thanks for your reply. BTW, with a bipolar pulse I meant just a single sign alternation, whereas apparently your definition is a sequence with an arbitrary number of sign alternations. Probably your definition is better. I considered the impact sound of the hammer, which sounds as if the body doesn't ring for longer than about 0.1 ms. However, that doesn't say much about the waveform.

Reply to
Arnold 

--
news:m6dfd4d3nc0pnood2o5ld5scv0958tfd5i@4ax.com

JF
Reply to
John Fields

John Fields

with an arbitrary number of sign alternations. Probably

John, I am not sure what you mean with that news message, but it cannot be found

Reply to
Arnold

It worked ok for me, it refers to some waveforms on alt.binaries.schematics.electronic also known as abse. Mike

Reply to
amdx

with an arbitrary number of sign alternations. Probably

--
That\'s the message ID of a USENET post which is on
alt.binaries.schematics.electronic and shows some high-voltage spikes
generated by a piezo igniter.

The reason you cant find it is because Google groups doesn\'t give you
access to binary newsgroups.

If you like, I can email it to you.

JF
Reply to
John Fields

with an arbitrary number of sign alternations. Probably

Thanks, please send it to this mail address: wmbever at yahoo.com. (I am using Outlook Express as well, but I don't know how to find a message by message-ID in OE either)

Reply to
Arnold 

--
Done.
Reply to
John Fields

Thanks. I see two superimposed waves: a high voltage wave (10 kV, 5 MHz, damped after a single period) and a medium voltage wave (0.4 kV,

70 kHz, damped after three periods). I agree with you that the medium voltage wave is a mechanical resonance of the igniter structure which is squeezing and stretching the piezo. However, as the medium voltage wave starts before the high voltage wave (which presumably marks the hammer impact), I guess it is caused by the hammer release.

Having read the wikipedia article on usenet, I guess the problem is that alt.binaries.schematics.electronic is not up to date on the news server of my ISP. After subscribing to it, my news agent receives only messages between mid august and september 5.

Reply to
Arnold

On second thought I not sure anymore that the high voltage (HV) signal marks the hammer impact. In that case the initial HV-peak should always be positive (or always be negative), as the ceramic is initially squeezed, but instead its sign varies at random.

Reply to
Arnold

"amdx" wrote in news:3fc4d$48d7efac$18d6b40c$26484 @KNOLOGY.NET:

Thank you for the clarification - it hadn't worked for me, and i also wasn't aware that ther was a NG for posting schematics. It might be a good learning tool ;)

- Kris

Reply to
Kris Krieger

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