[SOLVED] [Moved]: Help identifiing element

[hipi66]

Hi,
can anyone tell me what is this.
It's cathode (if I'm assuming correctly) is connected to +12VDC, and anode to + of piezo buzzer. Negative pole of buzzer is connected to GND.
On the schematic it's D2 (please ignore the values, they're not correct).

 

[betwixt]

Re: Help identifiing element

It's a MELF diode but without more information it is impossible to say exactly what kind. It could be simply to steer the current to the buzzer or it could be a zener diode to drop some voltage if the buzzer is a low voltage type.

Brian.

 

[hipi66]

Re: Help identifiing element

It's a MELF diode but without more information it is impossible to say exactly what kind. It could be simply to steer the current to the buzzer or it could be a zener diode to drop some voltage if the buzzer is a low voltage type.

Brian.

Thanks. Just one more question; as I can't be shure what it is, I'm sure that the first line is green which would point that it's Schottky. So can I just buy any Schottky and put it instead of this one?

Thank you, again.

 

[prestonee]

Re: Help identifiing element

could it be a BAV105... is a melf diode with green band, which is a high speed switching diode which to me makes a lot more sense in the signal path of a piezo buzzer then a schottky since a schottky could actually disrupt the signal.

 

[betwixt]

Re: Help identifiing element

The color of the band isn't an indication of the type of diode. Some do have several bands in which case they usually follow the resistor color code to get the digits and are preceeded with 1N or 1S. The one you show could be anything though. In series with a buzzer it is unlikely to be anything special, all it could possibly do is pass a few mA DC to the buzzer pins. I would guess it is probably a 'normal' small signal diode.

Brian.

 

[hipi66]

Re: Help identifiing element

It could be. (if I only didn't miss those diode classes...)
If I understand your point; it would be there to cut off any quiet/not stable sounds buzzer would create until voltage gets to appropriate level?
Then I should be safe with any generic like 1N4148.
Right?

 

[FvM]

Re: Help identifiing element

If the buzzer polarity is indicated correctly, only a zener diode makes sense. Do you see why?

 

[hipi66]

Re: Help identifiing element

I'm not sure what you're thinking off.
It could as well be the same reason as I posted in the last post.
The polarity can be seen on the third image.

 

[FvM]

A standard diode (e.g. 1N4148) won't allow any current flow to the buzzer.

 

[hipi66]

So what would?

Going to sleep. Thanks everyone for help.
Hopping to find the magic diode code in my inbox in the morning. :thumbsup:

 

[betwixt]

It does seem strange that any diode is there at all. Are you sure nothing else is connected between the buzzer and the diode?

That buzzer is a 12V type and is basically a small, highly resonant, loudspeaker, it does not produce sound by itself, you have to drive it with a pulsed DC voltage at around 2.4KHz. Except possibly to limit spikes from the inductance of the buzzer coil getting back to the driver circuit, it doesn't seem to have much purpose. It begs the question of what might be (but isn't) connected across it on the PCB layout.

FvM's point about the zener diode is one I missed. The band marks the cathode end of the diode and the '+' symbol marks the positive side of the buzzer, if joined together no current will flow through them. The exception would be a zener diode which conducts 'backwards' if the voltage exceeds it's Zener point. It could be used as a voltage dropper, for example if 24V was applied to the circuit and a 12V diode was used, it would drop 12V and leave the 12V across the buzzer. It would be an unusual circuit that did that though.

My guess is that something else connects at the junction of the diode and buzzer.

Brian.

 

[hipi66]

I'm sure that I got this part of the circuit correct, but I don't know what's on the other side of connector. And I'm 100% that there is nothing between the diode and the buzzer.
I'll try with 12V zener when I get the time to work on it.
Thanks guys for everything!

 

[betwixt]

I was only using 12V as an example, if it is a zener it could be anything from about 1V to 100V. The buzzer needs 12V so the zener would make up the diiference between 12V and whater voltage is feeding it.

Brian.

 

[hipi66]

:thumbsup:
You were right. I assumed that everything is 12V by measuring only before the switch.
Now I've measured everything else and it turns out it's ~25V.
So the 12V zener fits perfectly. (I've also measured the diode, now when I know what it is)

Thank you all!!!!!