Piezo ignitor pulse shape

[Arnold]

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
http://s365.photobucket.com/albums/oo98/jkien_photos/?action=view&current=IMG_6175.jpg
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?

 

[amdx]

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
http://s365.photobucket.com/albums/oo98/jkien_photos/?action=view&current=IMG_6175.jpg
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?

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

 

[Arnold]

  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

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.

 

[Jasen Betts]

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

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

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?

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.

Probably the pulse shape depends on its design,

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.

3) is the grey matter the piezo ceramic (PZT)?

that or a coating to protect it.

4) what is the purpose of the relativey large brass mass. Is it just a
heavy anvil?

I expect so.


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

Bye.
Jasen

 

[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 sparkgap
consider the sound it makes.

Bye.
   Jasen

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.

 

[Arnold]

John Fields

Arnold

---

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

 

[amdx]

John Fields

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

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

 

[Arnold]

---
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

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)

 

[Arnold]

---
You don't understand USENET.

Read this:

http://en.wikipedia.org/wiki/Usenet

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.

 

[Arnold]

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.

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.