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zener diode question

K

klem kedidelhopper

Jan 1, 1970
0
Aw, Philip. And there was me thinking that the vet had finally gotten your
meds just about right ... !

Never mind. We all know that it is actually you who is the fucking pig
ignorant moron, not just for what an offensive twat you are, but also
because despite knowing everything there could ever be to know, you have
actually, apparently, learnt nothing in your half arsed life. Sad ...
:)

Arfa

While I would have to agree with Phil's earlier statement that it
would be ideal to simply screw the diodes into threaded holes on the
heat sink, they are electrically in series, so that is not possible.
The heat sink is also mounted through the extra aluminum I've
subsequently added directly to the chassis, which of course is
building ground. So that would be another disaster. I liked the fan
idea, however sadly there is no room for it, not even a small CPU
cooler type. And while I would admit that this is not a "green" power
supply, once this heat issue is resolved it should be a reliable one.
In the interim I did take another look at my mounting arrangement
though and it appears that I may have used two plastic washers on the
one side of the diodes where I should have used mica. What sort of
brain fart spurned that idea I'll probably never know, but that might
be my problem. I may be attempting to transmit heat through plastic.
Duh? Anyway, If so it's apparently working, to some degree, but
obviously not enough degrees. I'll check this out tomorrow and update
this thread. Thank you for the link to the mounting kits Arfa, and to
everyone else for your input. Lenny
 
M

mike

Jan 1, 1970
0
It is, however, a technique quite often used in commercial equipment.
Whilst I would agree that it is not the most elegant, it does not have
to be "made" to work - it just does. I'm not quite sure I follow what
you think the problem is with the regulation. A zener diode produces a
more or less constant voltage drop across its (reverse biased) junction.
Yes, I would agree that the drop does vary a little with the current
flowing, but the drop is substantially constant, certainly enough so, if
you are not going to draw a huge range of currents through it, and
definitely not a problem if the 'dropper' is going to be followed by a
'real' regulator, as it was going to be in Klem's application, if you
remember from - or even read - his original thread from a couple of
months back.

He was looking for a simple solution because he did not fully understand
some of the more elegant and complicated ones that were being put to
him. As he had some high power zeners of an appropriate voltage to hand,
the solution that I offered him fitted the bill in that it was simple,
he understood it, and above all, it worked, and apparently has been
doing so for a couple of months now.

So, if you want a simple 'dropper' that is largely current independant,
then I think the term "slam dunk" fits this technique remarkably well !

Arfa
I can only recommend that you read the first sentence that you quoted.
My input has nothing to do with the dropper. It's about trying to get 12V
out of a AT PC supply without thinking about what you're doing.
 
P

Phil Allison

Jan 1, 1970
0
"Arfa Fuckwit TROLL Daily"
The correct way to mount them is exactly the same as you would a TO3
transistor. That is with a mica washer between the flat face of the stud
end and the heatsink, and a plastic top hat washer on the other side of
the heatsink, with the hole being large enough to accommodate the narrow
part of the insulator. I have mounted stud diodes like this many times,
and never had a problem.


** A TO3 device has a large surface area.

A DO4 stud device has almost none unless you include the thread.

So it is blindingly obvious that for best heatsinking, you screw them into a
threaded hole.

The heatsink may then need to be insulated from other metal work.

This is how all high power stud diodes zeners must be mounted, if you wish
to get anything like the maker's power ratings.

You colossally STUPID, BULLSHITTING pommy **** head.





.... Phil
 
K

klem kedidelhopper

Jan 1, 1970
0
   He's too ignorant to even consider the poor contact for a TO-3 with
two tiny screws on the ends, VS a 1/4x20 stud which can be torqued down
to give much better heat transfer.

I thought that I mentioned though that isolating the heat sink was not
an option. I think I can explain this a little better. The fins of the
heat sink are spaced about .50 inch apart. Between the fins are large
aluminum blocks I fashioned which increase the surface mating area.
These blocks are then mounted to two back to back pieces of .125 inch
aluminum each having a surface area of about 12 square inches. This
large contact area and equivalent thick piece of aluminum then bolts
to the chassis, It is these two pieces of stock which are the
"middle" of the sandwich, so to speak. The steel chassis also aids
with sinking some of the heat as well. Also as previously mentioned
both diodes are mounted on the heat sink so they must be isolated from
each other. There is also a thin coating of silicone grease on every
mating surface. One alternative to that would have been to use one
reverse polarity diode, (which I don't have), but then I would still
have to "float" the heat sink and it would be very impractical to try
to hang all this extra aluminum off the heat sink and come up with a
useable mounting method too. So this seemed like the best arrangement.
Lenny
 
J

Jamie

Jan 1, 1970
0
Arfa said:
He is not doing any clamping with his zener arrangement. It is a simple
constant voltage series dropper ...

Arfa

No matter, still in detonation mode.

Jamie
 
J

josephkk

Jan 1, 1970
0
I need to come up with a zener diode that will handle 1.0 amp
of current at 12V. I currently am using two 6.8V 10 watt stud
mount zeners in series mounted with insulators on a large
heatsink but it's pushing it. When the current spikes to 1.0 amp the
diodes get pretty hot.
Since I have a bag of these diodes Would it be a problem to
employ four of them in a series/parallel arrangement to attain
13.60V at 20watts? I realize that the exact voltage that each
diode "clips" at might be a bit different but would that really
matter? It would be a simple job to simply add one diode in parallel
with each one presently there. Thanks, Lenny

Perhaps a different zener diode a resistor or three and a really beefy
power transistor on a heatsink is a better method.

?-)
 
M

mike

Jan 1, 1970
0
"Arfa TOTAL FUCKWIT Daily"



** That is a blatantly false quote - you stinking, lying pommy cunthead.




** It is the only way to get the makers full power rating - as KK was
after.




** WFT is unconventional about a threaded hole in a heatsink for a stud
device ??




** The mere existence of insulation kits PROVES NOTHING !!

Real designers know that using such insulation means you must ** DE RATE *
the device.

In the case of a DO4 zener, it means by a large factor too.

All way over the head of the FUCKWIT TROLLS that post here.



.... Phil
May I recommend that, instead of name calling, you present some facts.
Sometimes, but not often on the internet, facts can quench the pissing
contest.

to wit

Let me apologize up front for including real math and a reference document.

According to the GE SCR manual Volume 3 page 272..
For a DO-4 size device
Thermal resistance of a metal-to-metal mount is 0.75 C/Watt.
Thermal resistance when using .005" mica insulation is 6.5 C/Watt.
Delta is 5.75 C/W
multiplied by 6.8W at 1A = 39.1 C additional temperature rise.

There's some ambiguity. They didn't mention whether they used a mica
insulator and heat spreading washer on the nut side. Their drawings
in other sections of the manual suggest that they sometimes use thermally
conductive paths on both sides of the metal. Other times the nut-side
is just a plastic or fiber washer to keep the stud centered in the hole.
That could make a significant difference. I suggest that the 39.1 C
might be an upper bound.

Only the user can decide if that raises the junction temperature
to be outside his design goals...or how that relates to the heatsink
to ambient thermal resistance and the ambient temperature. Or whether
adding a heat-spreading washer and bigger mica on either or both sides
would be worth trying.

It took me less time to look it up than to read your continuous stream
if nastiess.
I admit that it took me about an hour to disguise the outrage your
inputs evoke.
If you don't like the numbers, send your vitriol to GE.

Let me be clear...
I'm not defending the OP's design choices.
I wouldn't have done it that way.
But I am defending his right to ask for help without being attacked.

If not knowing...or being aggressively wrong...were not allowed
on the internet, there wouldn't be no newsgroups at all.
 
P

Phil Allison

Jan 1, 1970
0
"mike"
May I recommend that, instead of name calling, you present some facts.


** FFS - read the whole thread !!!!!!!!!!!

YOU are breaking ALL the rules of usenet !!!

Truth is - I posted simple facts and was abused for doing it by the
resident trolls.

Including YOU, fuckhead.


Let me apologize up front for including real math and a reference
document.


** You don't need maths to know that using insulation materials impedes the
flow of heat.

The maker of that 10W zener specs it at 10W only * IF * the case TEMP is not
more than 55C.

Note, not temp rise but TEMP !!

According to the GE SCR manual Volume 3 page 272..

** But this is not an SCR ....

For a DO-4 size device
Thermal resistance of a metal-to-metal mount is 0.75 C/Watt.
Thermal resistance when using .005" mica insulation is 6.5 C/Watt.
Delta is 5.75 C/W
multiplied by 6.8W at 1A = 39.1 C additional temperature rise.


** The maker's rating is 10 watts at 55C case temp.

http://www.datasheetcatalog.org/datasheet2/a/0a1whup4cfhdaygr9zxyqtaki7yy.pdf

" Power dissipation ( @ TC= 55C ) "

So, even IF the heatsink mounting point stays at room temp (25C) the max
case temp of 55C will be exceeded at 6 watts, if you use mica.

OTOH - if you use a threaded hole in the same heatsink, 55C is achievable
even at 10 watts, with a little fan cooling.

It took me less time to look it up than to read your continuous stream
if nastiess.

** FFS - read the thread.

The nastiness came from AD and YOU.

No-one ever asked me for any details.

Far as I am concerned, the impact of using mica ( et alia) insulators it is
common knowledge among all designers.

Which, of course, YOU and AD are NOT !!!!!

But I am defending his right to ask for help without being attacked.


** KK is a retarded lunatic.

He ignores expert help and does what he fucking feels like.

Then posts ridiculous lies about what that even is.

FFS wake up.

The old fool is a TROLL and so is AD.

TROLLS get no consideration from me.



.... Phil
 
"mike"





**  FFS   -   read the whole thread   !!!!!!!!!!!

 YOU are breaking ALL the rules of usenet  !!!

 Truth is -  I posted simple facts and was abused for doing it by the
resident trolls.

 Including YOU, fuckhead.


 ** You don't need maths to know that using insulation materials impedes the
flow of heat.

The maker of that 10W zener specs it at 10W only * IF * the case TEMP is not
more than 55C.

Note, not temp rise but  TEMP !!


** But this is not an SCR ....


** The maker's rating is 10 watts at 55C case temp.

http://www.datasheetcatalog.org/datasheet2/a/0a1whup4cfhdaygr9zxyqtak...

" Power dissipation ( @ TC= 55C ) "

So, even IF the heatsink mounting point stays at room temp (25C)  the max
case temp of 55C  will be exceeded at 6 watts, if you use mica.

OTOH  -  if you use a threaded hole in the same heatsink, 55C is achievable
even at 10 watts, with a little fan cooling.


**  FFS  -  read the thread.

The nastiness came from AD and YOU.

No-one ever asked me for any details.

Far as I am concerned, the impact of using mica ( et alia)  insulators it is
common knowledge among all designers.

Which, of course, YOU and AD are NOT !!!!!


** KK is a retarded lunatic.

He ignores expert help and does what he fucking feels like.

Then posts ridiculous lies about what that even is.

FFS wake up.

The old fool is a TROLL and so is AD.

TROLLS get no consideration from me.

...  Phil

Phil,

As a long-time lurker on this group, I have observed your postings for
years. You seem to initiate the namecalling as far as I can tell.
You would enjoy a much higher regard if you refrained from such
ascerbic postings. If you are technically right, that says a lot
about you, namecalling says a lot also, but not in the right way.
 
P

Phil Allison

Jan 1, 1970
0
"[email protected]"

As a long-time lurker on this group,

** Lurker = pompous shit head - right ?


I have observed your postings for years.


** But completely failed to comprehend even ONE of them.


You seem to initiate the name calling as far as I can tell.


** But you cannot tell very much.

Why have you not criticised AD for all his outrageous posts to me ??

You one of his loyal arse lickers ?

AD uses fake name, I use my real one and he is a massive bullshitter.


You would enjoy a much higher regard


** Who on earth wants to be held in regard by a bunch of lying fuckwits and
trolls ?

I refuse to be polite to such cretins - ever.

There is NOTHING to be gained by entertaining them - one cannot teach pigs
to sing.

TROLLS destroy newsgoups.

Piss off fool.


..... Phil
 
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