Re: zener diode

it may only serve as a clamp/clipper to hold the signal within the 5v logic
span the signal end up going to.

didn't the original mouse interface use rs232 protocols??,

and they used to be some really wild minus to positive levels for some weird
reason

try some standard 5.1 volt zeners (or 4.7volt)

and another thing ( i digress) why dont they come up with integer value of
zeners anyway?? if those semicon guys think they sooo smart!


"Allan Adler" <ara@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:y93ir34tjdg.fsf@xxxxxxxxxxxxxxxxxxxxxxx
Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx> writes:

Allan Adler wrote:
"HapticZ" <hapticz@xxxxxxxxxxxxx> writes:
is it text as a "zener" or a pictograph like a zener symbol?
is it like a Z with a crossbar thru it?
come forth with the info, we are intrigued...

The component has a label DZ2 next to it.

OK, that sounds fairly compelling.

Good.

The pcb legend will normally have some way of indicating polarity.
Typically some thicker print at one end which denotes the cathode.

Actually, I know the polarity too, even though there is no visible marking
that directly indicates it. The way I know the polarity is as follows:
(1) As you might guess from the notation DZ2, there is another Zener
diode,
labeled DZ1, and its polarity is clearly indicated by a standard
electrical symbol for a diode. So, we know the polarity of DZ1.
(2) Looking at the PCB with a 7x monocle shows that one end of DZ1 is
connected to one end of DZ2, and the other end of DZ1 is connected to
the other end of DZ2.
(3) This one-to-one correspondence between the leads of the two Zener
diodes
tells us the polarity of DZ2. It also tells us that they have the
same
Zener voltage.

Well, maybe things aren't exactly the way I have just described them.
The PCB certainly does have a label DZ1 and, in the rectangular space
allocated to DZ1 is a very clear electrical symbol for a diode. However,
I don't actually see a diode in that space, which is probably why I am
able
to see the very clear electrical symbol for a diode there. I do see two
little spots of solder filling the holes provided for DZ1, but there seem
to be lots of little holes on the PCB that are filled with solder and no
components.

So, it is more accurate to say that *if* there were a Zener diode at the
site
denoted DZ1, we would know its polarity and that its polarity would agree
with the polarity of DZ2. Since there is apparently no Zener diode at the
site denoted DZ1, we have a situation where a false statement can imply
any statement, but that's just mathematical logic: there should be no
doubt
that if they designed the board so that a Zener diode with that polarity
could go at the site DZ1, then any Zener diode whose leads are
electrically
connected, respectively, to the indicated leads of DZ1 must have that same
polarity as that prescribed for DZ1.

So, I'm fairly convinced that I know the polarity of DZ2, the Zener diode
that *is* there and which, because it is there, covers up whatever marking
it sits on that tells what its polarity is.

Now, there is one more detail that, in principle, should tell us the Zener
voltage of DZ2. That detail is that the leads of DZ2 are also,
respectively,
connected to two of the wires that join the mouse to the mouse port. This
mouse has what looks to me like a PS/2 connector. So, the Zener voltage
has
to be the voltage difference between two pins of the mouse port.

The wires are colored and the colors are all different, but I don't know
whether that reflects a color coding. The wires that connect to DZ2 are
respectively blue and green. To actually find out what wire is connected
to what pin, I either have to test for connectivity (which I'm not
equipped
to do at the moment) or I have to rip open the cable and see which pins
are
soldered to which wires, which I'd prefer not to do if I don't have to.

Maybe the only nonzero voltage difference between two pins of the mouse
port
always has to be 5 volts. Or maybe the only constant nonzero voltage
between
two pins of the mouse port always has to be 5 volts. Such a fact, if true,
would settle the question of the Zener voltage without my having to
measure anything.
--
Ignorantly,
Allan Adler <ara@xxxxxxxxxxxxxxxxxxxx>
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions
and
* comments do not reflect in any way on MIT. Also, I am nowhere near
Boston.


.

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