zener diode question

[Arfa Daily]

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:be2f7418-cd34-4319-8058-0d8f7b639249@g5g2000pbp.googlegroups.com...

On Apr 17, 11:14 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
Arfa Daily wrote:

Oh dear, he's off and running again. Go on Philip, scoot on back to the
vet
and tell him that you're hearing the voices and seeing the pretty
lights
again. Perhaps he will be able to up the level of your horse
tranquillizer
pills for a few days until you're suitably subdued ...

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

There is not a problem with your heatsink being grounded, as long as you use
the correct mounting hardware, in the correct way. It is not at all uncommon
for stud mounted diodes to be fitted into grounded heatsinks, just as it is
not uncommon for power transistors to be likewise mounted to grounded
heatsinks. As long as they are insulated, using mica washers at the heat
dissipative surfaces, everything will be fine.

You will see in the kits that I pointed to, that the insulating bush is just
a ring of plastic to fit over the stud, and stop it touching the sides of
the hole. With a mica washer top and bottom, along with a plain metal washer
(obviously smaller than the mica washer) on the underside, you then have as
much surface area as possible thermally connecting the stud device to both
sides of the heatsink. Despite Phil saying that the devices should only be
screwed straight into a threaded hole in a solid block, it is rare to see
DO4 devices fitted in such a way. They are almost invariably fitted
conventionally either directly to individual floating heatsinks or multiply
to grounded heatsinks using insulated mounting kits. This is the reason that
they come supplied with a nut, and hardware manufacturers make the
insulation kits ...

Arfa

 

[Phil Allison]

"Arfa TOTAL FUCKWIT Daily"

You will see in the kits that I pointed to, that the insulating bush is
just a ring of plastic to fit over the stud, and stop it touching the
sides of the hole. With a mica washer top and bottom, along with a plain
metal washer (obviously smaller than the mica washer) on the underside,
you then have as much surface area as possible thermally connecting the
stud device to both sides of the heatsink. Despite Phil saying that the
devices should only be screwed straight into a threaded hole in a solid
block,

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

it is rare to seeDO4 devices fitted in such a way.

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

They are almost invariably fitted conventionally

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

either directly to individual floating heatsinks or multiply to grounded
heatsinks using insulated mounting kits. This is the reason that they come
supplied with a nut, and hardware manufacturers make the insulation kits
...

** 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

 

[josephkk]

On Mon, 15 Apr 2013 08:12:06 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

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.

?-)

 

[mike]

On 4/17/2013 6:25 PM, Phil Allison wrote:

"Arfa TOTAL FUCKWIT Daily"

You will see in the kits that I pointed to, that the insulating bush is
just a ring of plastic to fit over the stud, and stop it touching the
sides of the hole. With a mica washer top and bottom, along with a plain
metal washer (obviously smaller than the mica washer) on the underside,
you then have as much surface area as possible thermally connecting the
stud device to both sides of the heatsink. Despite Phil saying that the
devices should only be screwed straight into a threaded hole in a solid
block,


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


it is rare to seeDO4 devices fitted in such a way.


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


They are almost invariably fitted conventionally


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


either directly to individual floating heatsinks or multiply to grounded
heatsinks using insulated mounting kits. This is the reason that they come
supplied with a nut, and hardware manufacturers make the insulation kits
...


** 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.

 

[Phil Allison]

"mike"

** 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.


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

 

[Phil Allison]

"hrhofann@sbcglobal.net"

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

 

[hrhofann@sbcglobal.net]

On Apr 17, 11:51 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

"mike"



** 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.

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/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.

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

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.

 

[Ian Field]

"hrhofann@sbcglobal.net" <hrhofmann@sbcglobal.net> wrote in message
news:0efeec08-8cc3-4a79-98e9-a34aa286a330@c14g2000yqh.googlegroups.com...

On Apr 17, 11:51 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"mike"



** 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.

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/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.

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

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.

He was raised by dingos.

 

[Michael A. Terrell]

Ian Field wrote:

hrhofann@sbcglobal.net wrote:

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.

He was raised by dingos.

Too bad they didn't just eat him, instead.