EEVblog #855 - Ceramic Capacitor Piezoelectric Effect

[EEVblog]

Dave investigates the piezoelectric effect in multi layer chip capacitors (MLCC's). In this case, on the backlight inverter on his own BM235 multimeter.

http://www.hycontek.com/attachments/LCD/DS-HY2613_TC.pdf

[ruffy91]

I didn't watch the video yet, but an interesting usage of high-capacitance X7R MLCCs is as micro-actuators: http://www.theiet.org/resources/journals/eletters/5007/nano-scale-mega-scope.cfm

[Barny]

Wouldn't be a blob of hot glue be a fix to?
The aditional mass would reduce the noice too.
Or am I wrong?

[MarvinTheMartian]

Wouldn't be a blob of hot glue be a fix to?

I in effect asked that too, but no-one responded.

It's not really a 'fix' as such (it doesn't resolve the design fault/parts selection issue) - it is more of a possible work around for those of us less experienced in circuit design and fault finding (ie yours truly )

Loved the explanation Dave and it gives me confidence to replace the cap concerned (if and when I get an appropriate cap). Will give me some more experience with re-working SMDs (where have those stronger glasses gone?  ).

[EEVblog]

Wouldn't be a blob of hot glue be a fix to?

Likely just attenuate it, which might be good enough of course.
The vibration is happening inside the cap and it's likely being amplified by the PCB itself.

[Muttley Snickers]

Would the act of just adding those temporary test wires alter the amplitude or the ringing frequency of the DUT  to any great extent ?.

Mine is due for a thorough modification service tomorrow.....

[bktemp]

The vibration is happening inside the cap and it's likely being amplified by the PCB itself.

The capacitor itself makes almost no noise. That's the same reason why piezo speakers are always mounted in some case or glued to some other plates to have a larger moving surface.
When searching for the culprit capacitor I am using tweezers to amplify the sound the same way the needle of a record player works:
I put one tip onto the capacitor while pressing onto the other end. This allows the tweezers to vibrate feely like a tuning fork.

[Artlav]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

[wraper]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

Earning money by selling a decent product?

[Muttley Snickers]

It's the vibe, and the squeal but mostly the vibe.

[Brumby]

[timgiles]

I was hoping a pair of Tantalums would be ok, just ordered two Kemet SMD Tantalum Capacitor 35V SMT (3 Packs) 1 and 10uF.

[Barbossa404]

This reminds me of http://thume.ca/screentunes/ (https://github.com/trishume/screentunes for a description), which uses patterns on the screen to generate a modulated and surprisingly loud humming on most lcd screens (led backlight preferred). Same effect but most people don't expect a whining pc screen after they replaced their CRTs 

[idpromnut]

Thanks for the video Dave!    I was going to do a follow-on video trying to mic the sound from my unit, as even with C44 removed, I can still hear a very very faint whine coming from somewhere (only with the case open, and even then it's faint), probably from C43. Excellent scope captures; that is probably something I should have worked on for my video.

Also nice to hear the IRC channel mentioned

[Fungus]

Are you going to include a replacement cap with every meter?

 

[max666]

What about flip it 90 degrees? So the vibrating axis will not be stretching the PCB.

I'm curious as well how flipping the cap would affect this issue.

[Radio Tech]

I quite enjoyed that Dave.   

[EEVblog]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

I like the meter, I want to sell it, I think it's good enough to put my name on it, I think it's cool to have a meter I can use in my video that has my brand on it, a lot of people get a kick out of having an EEVblog branded meter, and it helps feed my family. Is there anything wrong with that?
If you don't want to buy one from me that's fine, buy the regular BM235 (I deliberately didn't hide the fact that it's the same as the regular BM235). If you do want to buy one from me with the EEVblog name on it, then great, here it is. If you think its crap, that's fine too. Name an equivalent model meter on the market that you can officially get the schematic of.

[EEVblog]

even with C44 removed, I can still hear a very very faint whine coming from somewhere (only with the case open, and even then it's faint), probably from C43.

Not probably, 100% certainty. There is nothing else in the backlight circuit.

[woox2k]

I can use in my video that has my brand on it,

Nothing wrong with that but i hope you will not choose to use that meter just for that fact even though you might have better meters around that would do the task a bit better. At least i would still like to see real examples where some high-end DMM's do a better task. Thing i'm asking is not to over-advertise it (not saying you do it now, just don't start doing it) 
That said, i would gladly pay a bit more for a DMM knowing that some of that goes directly to you, seeing it "over-advertised" on the video would not change the fact at all.

By the way, where is the unofficial EEVBlog IRC channel you mentioned in the video?

[idpromnut]

By the way, where is the unofficial EEVBlog IRC channel you mentioned in the video?

In #eevblog on Afternet https://www.afternet.org/

[lapm]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

Its the official EEVBLOG merchandise... It has Logo on it... There's people that buy directional audio cables, this multimeter is much better purchase and support out favorite video blogger about electronics.
 

[dentaku]

One squeaky thing that annoys me is Indiglow like I have on my Timex watch. It squeaks quite loudly just like that capacitor.
I once saw a remote control that had a light-up face that would activate whenever it was moved. I couldn't stand it 

[arekm]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

[Artlav]

Is there anything wrong with that?

Nope, perfectly fine.
I just got an impression over the last few videos that you made your own multimeter (you kept mentioning a "secret project" here and there for the past few months) and the illusion went splat on this video.