high voltage by 78

[Vexator]

How could I regulate 190 V DC whit a 78xx? I knew these devices can be used
at this high voltage.



--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

..

 

[CFoley1064]

Subject: high voltage by 78
From: "Vexator" vexator_nospam@inwind.it
Date: 9/11/2004 3:09 AM Central Daylight Time
Message-id: <Coy0d.5370$6b4.152712@twister1.libero.it

How could I regulate 190 V DC whit a 78xx? I knew these devices can be used
at this high voltage.



--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

I believe you mean "Memento Audere Semper" (remember always to be daring or
audacious). That's what happens when you copy mottoes off statues.

The LMXX regulators are good for 35V maximum input voltage. You could shoehorn
one into a scheme for a 190VDC linear regulator, but it would be more trouble
than it's worth. Even as a reference voltage, you'd have to provide a
preregulator to keep from smoking it.

It's possible you saw a 7812 or 7805 as the IC that provided the low voltage
power for the control circuitry in the high voltage power supply you were
looking at.

Be careful. High voltage kills.

Chris

 

[Gary Lecomte]

"Vexator" <vexator_nospam@inwind.it> wrote in message news:<Coy0d.5370$6b4.152712@twister1.libero.it>...

How could I regulate 190 V DC whit a 78xx? I knew these devices can be used
at this high voltage.

It is Possible, Using a High Voltage Value, Zener in the ground lead
to Ground. But it Requires Special Care with the Current Draw at that
voltage.

 

[Michael Black]

CFoley1064 (cfoley1064@aol.com) writes:

Subject: high voltage by 78
From: "Vexator" vexator_nospam@inwind.it
Date: 9/11/2004 3:09 AM Central Daylight Time
Message-id: <Coy0d.5370$6b4.152712@twister1.libero.it

How could I regulate 190 V DC whit a 78xx? I knew these devices can be used
at this high voltage.



--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

I believe you mean "Memento Audere Semper" (remember always to be daring or
audacious). That's what happens when you copy mottoes off statues.

The LMXX regulators are good for 35V maximum input voltage. You could shoehorn
one into a scheme for a 190VDC linear regulator, but it would be more trouble
than it's worth. Even as a reference voltage, you'd have to provide a
preregulator to keep from smoking it.

It's possible you saw a 7812 or 7805 as the IC that provided the low voltage
power for the control circuitry in the high voltage power supply you were
looking at.

Be careful. High voltage kills.

Chris

I figured he was thinking of the LM317, which because of its different

arrangement, can regulate much higher voltage. I'm not sure of the limit.
I'm sure it's spelled out in the datasheet.

Michael

 

[Joe McElvenney]

Hi,

I believe you mean "Memento Audere Semper" (remember always to be daring or
audacious). That's what happens when you copy mottoes off statues.

The script on Roman statues would have used the letter 'V'
not 'U'

A 'smilee' on the other hand would not be found there unless
it was spray-painted on.


Cheers - Joe

 

[Robert C Monsen]

"Vexator" <vexator_nospam@inwind.it> wrote in message
news:Coy0d.5370$6b4.152712@twister1.libero.it...

How could I regulate 190 V DC whit a 78xx? I knew these devices can
be used
at this high voltage.

These devices attempt to keep a constant voltage between their common
input and output. Thus, you might be able to make a high voltage
regulator by floating them, like this:

.--------.
Vin | |
----o 78xx o----o---------.
| | | |
'----o---' .-. |
| | | |
| | | |
| '-' |
| | |
'--------o |
| |
.-. .-.
| | | | Load
| | | |
'-' '-'
| |
GND ------------------o---------'

created by Andy´s ASCII-Circuit v1.25.250804 www.tech-chat.de

The voltage divider forces the device to attempt to create a voltage
of xx volts across the top resistor.

I haven't considered startup situations, or high load currents.

Regards,
Bob Monsen

 

[Tom Biasi]

"Joe McElvenney" <ximac@btinternet.com> wrote in message
news:VA.0000005c.0026d43f@btinternet.com...

Hi,

I believe you mean "Memento Audere Semper" (remember always to be daring
or
audacious). That's what happens when you copy mottoes off statues.


The script on Roman statues would have used the letter 'V'
not 'U'

A 'smilee' on the other hand would not be found there unless
it was spray-painted on.


Cheers - Joe


You are correct sir. "In God We Trvst."

I'm not so sure about the smilie face, those Romans were wild and crazy
guys.

 

[Vexator]

Why does "MEMENTO AVDERE SEMPER" excite curiosity? It's 'cos latin?
That motto was wrote by Gabriele D'Annunzio, do u know that poet?


--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

..
"Tom Biasi" <tombiasi@REMOVETHISoptonline.net> ha scritto nel messaggio
news:hPH0d.24844$bE1.12549445@news4.srv.hcvlny.cv.net...

"Joe McElvenney" <ximac@btinternet.com> wrote in message
news:VA.0000005c.0026d43f@btinternet.com...
Hi,

I believe you mean "Memento Audere Semper" (remember always to be
daring
or
audacious). That's what happens when you copy mottoes off statues.


The script on Roman statues would have used the letter 'V'
not 'U'

A 'smilee' on the other hand would not be found there unless
it was spray-painted on.


Cheers - Joe


You are correct sir. "In God We Trvst."
I'm not so sure about the smilie face, those Romans were wild and crazy
guys.

 

[Vexator]

thanks all. Now I understand.
example:
I need 190VDC, so using a 7824 and Im going to put one 166V zener between
common and gnd, is it ok?

--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

..
"Robert C Monsen" <rcsurname@comcast.net> ha scritto nel messaggio
news:ABH0d.28351$D%.14076@attbi_s51...

"Vexator" <vexator_nospam@inwind.it> wrote in message
news:Coy0d.5370$6b4.152712@twister1.libero.it...
How could I regulate 190 V DC whit a 78xx? I knew these devices can
be used
at this high voltage.


These devices attempt to keep a constant voltage between their common
input and output. Thus, you might be able to make a high voltage
regulator by floating them, like this:

.--------.
Vin | |
----o 78xx o----o---------.
| | | |
'----o---' .-. |
| | | |
| | | |
| '-' |
| | |
'--------o |
| |
.-. .-.
| | | | Load
| | | |
'-' '-'
| |
GND ------------------o---------'

created by Andy´s ASCII-Circuit v1.25.250804 www.tech-chat.de

The voltage divider forces the device to attempt to create a voltage
of xx volts across the top resistor.

I haven't considered startup situations, or high load currents.

Regards,
Bob Monsen

 

[CFoley1064]

Subject: Re: high voltage by 78
From: "Vexator" vexator_nospam@inwind.it
Date: 9/12/2004 4:54 AM Central Daylight Time
Message-id: <l1V0d.89707$1V3.2202131@twister2.libero.it

thanks all. Now I understand.
example:
I need 190VDC, so using a 7824 and Im going to put one 166V zener between
common and gnd, is it ok?

--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

Mottoes are curious things, I guess. I personally prefer the one etched on the
sword of Oscar of Gordon, Hero of Heinlein's "Glory Road" (1963) (view in fixed
font or M$ Notepad) ;-) :

"Dum vivimus, Vivamus"
or
"While we live, let us live!"

Very appropriate for those who want to vigorously seek out and enjoy the best
things in life, as well as those working with high voltage.

But seriously, the idea of just placing a 166V zener in series with the GND
terminal of a 7824 isn't going to cut it. Among other things, a 1uF output cap
is required to stabilize the output. At turn-on, you'll have 190V between IN
and OUT, and smoke. There are other reasons why it just won't work, but that
will do.

If you really need 190VDC at small current (0 to 15 mA), you might want to try
something like this (view in fixed font or M$ Notepad):

Q&D 190VDC Supply 4700 Ohm
20 Watt 192VDC
_/ ____ 1N4007 ___ +
o -o/ o--|_--_|-. ,-------. ,--o-----o---->|-o-|___|-o-------o
1/4A )|( )|( | | | + |
)|( )|( | | ### -
.-'|( )|'----. | --- ^
| |( )| | | | | |
'-.|( )|,--' | | ___ | String of
)|( )|( | .---|___|-o | Sixteen
)|( )|( | | | 100 | 1N4742
o----------------' '-------' '----o-' | 2W | + | (12V Zener)
120/240V Pri | ### -
12V Sec | --- ^
X 2 | | |
'----|<-o-------o-------o
1N4007 -
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Here's the drill. This circuit will work if you've got 120VAC or 240VAC line
voltage. Get two dual-primary transformers of 12VA or higher rating. The ones
pictured are 12VAC secondary at 1A. Use the first one to "back-feed" the
second, resulting in an isolated high AC voltage at the output (in the
illustration, I assume 240VAC, so the "secondaries" of the second transformer
are wired in parallel to give 120VAC output).

Use two diodes and two 22uF, 250VDC caps as shown to give you 340V pk., which
is dropped by the 4700 ohm 20 watt series resistor to give you about 192VDC
acrioss the string of 16 ea. 12V, 1W zeners. If your output's a little high or
low, tweak by replacing the last zeners in the chain with 10V (1N4740) or 15V
(1N4744). This circuit is good for 0 to 15 mA, won't crash and burn if it
accidentally short-circuits, and is isolated from the line. This can be
improved by putting a 100K 1/2 watt resistor across each of the 250V caps to
help with load sharing. But it's a good start.

Again, please be careful here. The switch and 1/4A fuse above are not
optional. Even isolated high voltage can be dangerous. If you don't know what
you're doing, stop and find out. The "stupid" questions are only stupid if you
don't know and _don't_ ask them. Have somebody else in the room while you're
fiddling who knows where the switch is. And do remember Nikolai Tesla's
advice, and use one hand to grab your belt behind your back whenever the
voltage is on.

DVM VIVIMVS, VIVAMVS (I prefer Fluke ;-) )
Chris

 

[colin]

"Vexator" <vexator_nospam@inwind.it> wrote in message
news:Coy0d.5370$6b4.152712@twister1.libero.it...

How could I regulate 190 V DC whit a 78xx? I knew these devices can be
used
at this high voltage.



--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

.

You would probably have to use a high voltage transistor to ensure the input
to the regulator remains within the 35v rating.
you may find that even with a zener, or floating the regulator, the change
in unregulated voltage may exced its rating otherwise.

If you look through the many voltage regulator spec sheets youl find some
have an amasing colection of novel and useful circuit applications.

Colin =^.^=

 

[Gene]

......... those Romans were wild and crazy guys.
Uhm, do you really think that one has to be "wild and crazy" to created an

empire that lasted 1,000 years?
Gene

 

[Rich Grise]

On Saturday 11 September 2004 07:38 am, Michael Black did deign to grace us
with the following:

CFoley1064 (cfoley1064@aol.com) writes:
Subject: high voltage by 78
From: "Vexator" vexator_nospam@inwind.it
Date: 9/11/2004 3:09 AM Central Daylight Time
Message-id: <Coy0d.5370$6b4.152712@twister1.libero.it

Be careful. High voltage kills.

Chris

I figured he was thinking of the LM317, which because of its different
arrangement, can regulate much higher voltage. I'm not sure of the limit.
I'm sure it's spelled out in the datasheet.

The only "limit" on either is the voltage across the chip itself. You could

use a 7812 to regulate 190V, as long as the supply doesn't go over 225V or
under about 193, and you have a stiff reference at +178V. (Include all the
rest of the standard caveats/disclaimers, of course.)

HTH!
Rich

 

[Rich Grise]

On Sunday 12 September 2004 11:12 am, CFoley1064 did deign to grace us with
the following:

Again, please be careful here. The switch and 1/4A fuse above are not
optional. Even isolated high voltage can be dangerous. If you don't know
what
you're doing, stop and find out. The "stupid" questions are only stupid
if you
don't know and _don't_ ask them. Have somebody else in the room while
you're
fiddling who knows where the switch is. And do remember Nikolai Tesla's
advice, and use one hand to grab your belt behind your back whenever the
voltage is on.

I can corroborate this. When I was in the USAF as an electronics tech, we

were required by regulation to take off all jewelry, i.e. rings/watches,
and keep one hand in our pocket. They didn't even like us to wear our dog
tags.

Another little thing you can do is ground one finger while poking
around - like, let your little finger rest against the chassis, as
if you're steadying the probe - that way, when you get zapped, you
get a burn on your hand, rather than cardiac arrest.

Good Luck!
Rich

 

[Vexator]

Hi Chris,
thank you! ...

**** The "stupid" questions are only stupid if you don't know and _don't_
ask them **** that is a good motto!!!

thanks again if you lost time to me, your advices are my precious.

--
MEMENTO AVDERE SEMPER
Giovanni (Italy)

..

"CFoley1064" <cfoley1064@aol.com> ha scritto nel messaggio
news:20040912141215.08200.00000549@mb-m06.aol.com...

Subject: Re: high voltage by 78
From: "Vexator" vexator_nospam@inwind.it
Date: 9/12/2004 4:54 AM Central Daylight Time
Message-id: <l1V0d.89707$1V3.2202131@twister2.libero.it

thanks all. Now I understand.
example:
I need 190VDC, so using a 7824 and Im going to put one 166V zener between
common and gnd, is it ok?

--
MEMENTO AVDERE SEMPER
Giovanni (Italy)


Mottoes are curious things, I guess. I personally prefer the one etched
on the
sword of Oscar of Gordon, Hero of Heinlein's "Glory Road" (1963) (view in
fixed
font or M$ Notepad) ;-) :

"Dum vivimus, Vivamus"
or
"While we live, let us live!"

Very appropriate for those who want to vigorously seek out and enjoy the
best
things in life, as well as those working with high voltage.

But seriously, the idea of just placing a 166V zener in series with the
GND
terminal of a 7824 isn't going to cut it. Among other things, a 1uF
output cap
is required to stabilize the output. At turn-on, you'll have 190V between
IN
and OUT, and smoke. There are other reasons why it just won't work, but
that
will do.

If you really need 190VDC at small current (0 to 15 mA), you might want to
try
something like this (view in fixed font or M$ Notepad):

Q&D 190VDC Supply 4700 Ohm
20 Watt 192VDC
_/ ____ 1N4007 ___ +
o -o/ o--|_--_|-. ,-------. ,--o-----o---->|-o-|___|-o-------o
1/4A )|( )|( | | | + |
)|( )|( | | ### -
.-'|( )|'----. | --- ^
| |( )| | | | | |
'-.|( )|,--' | | ___ | String of
)|( )|( | .---|___|-o | Sixteen
)|( )|( | | | 100 | 1N4742
o----------------' '-------' '----o-' | 2W | + | (12V Zener)
120/240V Pri | ### -
12V Sec | --- ^
X 2 | | |
'----|<-o-------o-------o
1N4007 -
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Here's the drill. This circuit will work if you've got 120VAC or 240VAC
line
voltage. Get two dual-primary transformers of 12VA or higher rating. The
ones
pictured are 12VAC secondary at 1A. Use the first one to "back-feed" the
second, resulting in an isolated high AC voltage at the output (in the
illustration, I assume 240VAC, so the "secondaries" of the second
transformer
are wired in parallel to give 120VAC output).

Use two diodes and two 22uF, 250VDC caps as shown to give you 340V pk.,
which
is dropped by the 4700 ohm 20 watt series resistor to give you about
192VDC
acrioss the string of 16 ea. 12V, 1W zeners. If your output's a little
high or
low, tweak by replacing the last zeners in the chain with 10V (1N4740) or
15V
(1N4744). This circuit is good for 0 to 15 mA, won't crash and burn if it
accidentally short-circuits, and is isolated from the line. This can be
improved by putting a 100K 1/2 watt resistor across each of the 250V caps
to
help with load sharing. But it's a good start.

Again, please be careful here. The switch and 1/4A fuse above are not
optional. Even isolated high voltage can be dangerous. If you don't know
what
you're doing, stop and find out. The "stupid" questions are only stupid
if you
don't know and _don't_ ask them. Have somebody else in the room while
you're
fiddling who knows where the switch is. And do remember Nikolai Tesla's
advice, and use one hand to grab your belt behind your back whenever the
voltage is on.

DVM VIVIMVS, VIVAMVS (I prefer Fluke ;-) )
Chris

 

[Tom Biasi]

"Gene" <email@private.net> wrote in message
news:7331d.19486$Fz.16055@newssvr29.news.prodigy.com...

......... those Romans were wild and crazy guys.
Uhm, do you really think that one has to be "wild and crazy" to created an
empire that lasted 1,000 years?
Gene
No. But it helps