Do 2 x 1 watt diodes = 1x 2 watt ZD?

[shannell]

I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?

 

[Ken Taylor]

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...

I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?

In theory, yes, but it's not a good practice as they aren't perfect devices

and won't load share 100%. What are you actually trying to do? There may be
a better solution.

Ken

 

[shannell]

Hi, I am trying to quieten the 80mm 12v fans on a CRT projector.
Any reccommendations? Dick smith only had the 1 watters...

"Ken Taylor" <ken123@xtra.co.nz> wrote in message
news:S0klb.186249$JA5.4641669@news.xtra.co.nz...

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v
ZD?

In theory, yes, but it's not a good practice as they aren't perfect
devices
and won't load share 100%. What are you actually trying to do? There may
be
a better solution.

Ken

 

[Justin Thyme]

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...

I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?
Unfortunately no - they have a tolerance in them, so one might be 5.11v and

the other 5.09v. When they are in parallel, the 5.09v one will take all the
current, because the voltage is still below the threshold of the 5.11v.
Consequently one zener will be drastically overloaded while the other does
nothing at all.
There are ways around it however - careful use of appropriate value
resistors can overcome the problem. i'm not the best at doing ascii circuit
diagrams, and it's maybe a little hard to explain. if you want more info
i'll post a sketch on the web and give you a link.
Alternatively - have you considered the use of 7805 devices? - they are
simple to design around and can comfortably deliver fairly high currents -
up to 1A with suitable heatsinking.

 

[Rod Speed]

"Justin Thyme" <pleasedontspamme@nowhere.com> wrote in message news:3f95f385@news.comindico.com.au...

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?
Unfortunately no - they have a tolerance in them, so one might be 5.11v and
the other 5.09v. When they are in parallel, the 5.09v one will take all the
current, because the voltage is still below the threshold of the 5.11v.
Consequently one zener will be drastically overloaded while the other does
nothing at all.

Not in his situation where he's just chucking some voltage away.

It should work well enough.

There are ways around it however - careful use of appropriate value
resistors can overcome the problem. i'm not the best at doing ascii circuit
diagrams, and it's maybe a little hard to explain. if you want more info
i'll post a sketch on the web and give you a link.
Alternatively - have you considered the use of 7805 devices? - they are
simple to design around and can comfortably deliver fairly high currents -
up to 1A with suitable heatsinking.

 

[James Fenech]

Hello,

A better bet may be two lower voltage zenner in series.

James.

"Rod Speed" <rod_speed@yahoo.com> wrote in message
news:bn4vu3$tevhm$1@ID-69072.news.uni-berlin.de...

"Justin Thyme" <pleasedontspamme@nowhere.com> wrote in message
news:3f95f385@news.comindico.com.au...

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v
ZD?
Unfortunately no - they have a tolerance in them, so one might be 5.11v
and
the other 5.09v. When they are in parallel, the 5.09v one will take all
the
current, because the voltage is still below the threshold of the 5.11v.
Consequently one zener will be drastically overloaded while the other
does
nothing at all.

Not in his situation where he's just chucking some voltage away.

It should work well enough.

There are ways around it however - careful use of appropriate value
resistors can overcome the problem. i'm not the best at doing ascii
circuit
diagrams, and it's maybe a little hard to explain. if you want more info
i'll post a sketch on the web and give you a link.
Alternatively - have you considered the use of 7805 devices? - they are
simple to design around and can comfortably deliver fairly high
currents -
up to 1A with suitable heatsinking.

 

[Joseph Webster]

Would be better to put two with half voltage in series.
Much more tolerant to small differences between diodes.

JLW

shannell wrote:

I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?

 

[Rod Speed]

"James Fenech" <james.fenech@xxxnec.com.au> wrote in message news:1066800585.732735@proxy.nec.com.au...

Hello,

A better bet may be two lower voltage zenner in series.

True. Dunno how available they are tho.

"Rod Speed" <rod_speed@yahoo.com> wrote in message
news:bn4vu3$tevhm$1@ID-69072.news.uni-berlin.de...

"Justin Thyme" <pleasedontspamme@nowhere.com> wrote in message
news:3f95f385@news.comindico.com.au...

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v
ZD?
Unfortunately no - they have a tolerance in them, so one might be 5.11v
and
the other 5.09v. When they are in parallel, the 5.09v one will take all
the
current, because the voltage is still below the threshold of the 5.11v.
Consequently one zener will be drastically overloaded while the other
does
nothing at all.

Not in his situation where he's just chucking some voltage away.

It should work well enough.

There are ways around it however - careful use of appropriate value
resistors can overcome the problem. i'm not the best at doing ascii
circuit
diagrams, and it's maybe a little hard to explain. if you want more info
i'll post a sketch on the web and give you a link.
Alternatively - have you considered the use of 7805 devices? - they are
simple to design around and can comfortably deliver fairly high
currents -
up to 1A with suitable heatsinking.

 

[amstereo - matt2]

crt projectors get HOT!!! do you really want to put more heat stress on the
unit, best thing to do is get a quieter fan or mod the air-flow path a bit.
"shannell" <sjs@nella.net.au> wrote in message
news:3f95d1d7$1@usenet.per.paradox.net.au...

Hi, I am trying to quieten the 80mm 12v fans on a CRT projector.
Any reccommendations? Dick smith only had the 1 watters...

"Ken Taylor" <ken123@xtra.co.nz> wrote in message
news:S0klb.186249$JA5.4641669@news.xtra.co.nz...
"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v
ZD?

In theory, yes, but it's not a good practice as they aren't perfect
devices
and won't load share 100%. What are you actually trying to do? There may
be
a better solution.

Ken

 

[Franc Zabkar]

On Wed, 22 Oct 2003 14:08:25 +1000, "Rod Speed" <rod_speed@yahoo.com>
put finger to keyboard and composed:

"Justin Thyme" <pleasedontspamme@nowhere.com> wrote in message news:3f95f385@news.comindico.com.au...

"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?
Unfortunately no - they have a tolerance in them, so one might be 5.11v and
the other 5.09v. When they are in parallel, the 5.09v one will take all the
current, because the voltage is still below the threshold of the 5.11v.
Consequently one zener will be drastically overloaded while the other does
nothing at all.

Not in his situation where he's just chucking some voltage away.

"Chucking some voltage away"? What a load of gibberish.

It should work well enough.

No, it is a silly idea.

There are ways around it however - careful use of appropriate value
resistors can overcome the problem. i'm not the best at doing ascii circuit
diagrams, and it's maybe a little hard to explain. if you want more info
i'll post a sketch on the web and give you a link.
Alternatively - have you considered the use of 7805 devices? - they are
simple to design around and can comfortably deliver fairly high currents -
up to 1A with suitable heatsinking.

- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Spajky]

On Wed, 22 Oct 2003 10:09:58 +0930, "shannell" <sjs@nella.net.au>
wrote:

Hi, I am trying to quieten the 80mm 12v fans on a CRT projector.
Any reccommendations? Dick smith only had the 1 watters...

see my site under electronics; fan stuff II next page, dirty zener
enhancement ...

-- Regards, SPAJKY
& visit site - http://www.spajky.vze.com
Celly-III OC-ed,"Tualatin on BX-Slot1-MoBo!"
E-mail AntiSpam: remove ##

 

[John Crighton]

On Wed, 22 Oct 2003 10:09:58 +0930, "shannell" <sjs@nella.net.au>
wrote:

"Ken Taylor" <ken123@xtra.co.nz> wrote in message
news:S0klb.186249$JA5.4641669@news.xtra.co.nz...
"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v
ZD?

In theory, yes, but it's not a good practice as they aren't perfect
devices
and won't load share 100%. What are you actually trying to do? There may
be
a better solution.

Ken



Hi, I am trying to quieten the 80mm 12v fans on a CRT projector.
Any reccommendations? Dick smith only had the 1 watters...

Hello Shannell,
Ken's question was spot on.
Have a look here for starters.
http://casemods.pointofnoreturn.org/pwm/index.html
Have a look at the LM317 tutorial if you don't like the PWM circuits.

If you don't like the LM317 idea, maybe a string of several ordinary
diodes in series would do. You could mount them on a rotary
switch. Introduce roughly 0.8 volt (drop across each diode) on
each click of the switch till the fan noise reduces to suit you.

I see DSE has 1 amp diodes for 7 cents each and 3 amp diodes
for 25 cents. How much current does your fan draw?
Find out and choose your diodes.

Here is another site where the author has gone
into this fan noise problem in a big way also.
http://www.cpemma.co.uk/index.html

Have fun!

Regards,
John Crighton
Hornsby

 

shannell wrote:

Hi, I am trying to quieten the 80mm 12v fans on a CRT projector.
Any reccommendations? Dick smith only had the 1 watters...

Reduction of the airflow into the projector could shorten the lifetime
of some components due to elevated heating of these components. These
could be lamps, the crts, which would probably depend on circulation
of cooling fluids on the screen of the tube via convection anyway,
electrolytic capacitors, most semiconductors, etc.

If you can try to find out the manufacturer of the fans, and the model
of the fan, then you can identify the amount of airflow the fan pushes
into the projector. You could then attempt to select a low noise fan
that has an airflow (typically measured in litres/minute|hour) that
is equivalent or greater than the existing fans. Low noise fans typically
have lower flow rates than equivalent size fans.

RS Components and Farnell have a selection of 80mm fans, both 240 volt ac,
and 12 volt dc. Others in this ng could recommend other suppliers.

Then again, if you modify the projector in any way, you could void the
warranty, if it's still valid. If it's out of the warranty period, then
I'd recommend you employ a qualified tv technician/repairman to carry
out the required modifications. Also, there may be a modification
sheet from the projector manufacturer that details how to fix a noisy
fan problem.

--

Regards
David

=================================
Reply to

dmmilne at ozemail dot com dot au

 

[Arpit]

use a slower speed 120mm fan. quieter, and more airflow.

On Wed, 22 Oct 2003 09:37:47 +0930, "shannell" <sjs@nella.net.au>
wrote:

I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v ZD?

 

[Rod Speed]

Some stupid wog claiming to be
Franc Zabkar <fzabkar@optussnet.com.au> wrote in
message news:34jcpv0drgqieaum22vb6qrl1tt21htdvr@4ax.com...
just the puerile shit thats always pouring from its lard arse.

 

[Franc Zabkar]

On Wed, 22 Oct 2003 10:09:58 +0930, "shannell" <sjs@nella.net.au> put
finger to keyboard and composed:

Hi, I am trying to quieten the 80mm 12v fans on a CRT projector.
Any reccommendations? Dick smith only had the 1 watters...

FWIW, WES Components have 5W, 5.1V Zeners for ~$1 each. You could also
make up a string of eight 1N4004 diodes in series. Having said that, I
believe reducing the airflow is not a good idea.

"Ken Taylor" <ken123@xtra.co.nz> wrote in message
news:S0klb.186249$JA5.4641669@news.xtra.co.nz...
"shannell" <sjs@nella.net.au> wrote in message
news:3f95ca4c$1@usenet.per.paradox.net.au...
I am trying to get a 2 watt 5.1 volt zener diode, I bought 2 x 1 watt
zener
diodes, if I put them in parrallel, do they work the same as a 2w 5.1v
ZD?

In theory, yes, but it's not a good practice as they aren't perfect
devices
and won't load share 100%. What are you actually trying to do? There may
be
a better solution.

Ken

- Franc Zabkar
--
Please remove one 's' from my address when replying by email.