too easy of a question

[Tater Schuld]

I have a device that says it runs on 6-12 volts dc. I'd like to hook it up
to a car battery, but the alternators on such things exceed 12 volts (and
the battery at its 13.8).

So I should be able to hook a LM7812 and be good to go, right? or would the
13.8 be too low for regulation. also these devices are going to be run along
some long lengths of wire, so I'll probably stick the regulator next to the
device, rather than near the battery. maybe stick to the lm7809 instead?

 

[Art]

If the device will operate over that range another 1.8 volt will not destroy
it.
"Tater Schuld" <Tater1337@yahoo.com> wrote in message
news:lieFf.115$Hr4.100@fe03.lga...

I have a device that says it runs on 6-12 volts dc. I'd like to hook it up
to a car battery, but the alternators on such things exceed 12 volts (and
the battery at its 13.8).

So I should be able to hook a LM7812 and be good to go, right? or would
the 13.8 be too low for regulation. also these devices are going to be run
along some long lengths of wire, so I'll probably stick the regulator next
to the device, rather than near the battery. maybe stick to the lm7809
instead?

 

[Bob Monsen]

On Sat, 04 Feb 2006 21:29:26 -0600, Tater Schuld wrote:

I have a device that says it runs on 6-12 volts dc. I'd like to hook it up
to a car battery, but the alternators on such things exceed 12 volts (and
the battery at its 13.8).

So I should be able to hook a LM7812 and be good to go, right? or would the
13.8 be too low for regulation. also these devices are going to be run along
some long lengths of wire, so I'll probably stick the regulator next to the
device, rather than near the battery. maybe stick to the lm7809 instead?

If it runs on 6V-12V, it almost certainly has a regulator in it already.
That means that you might be able to simply hook it up.

However, if you are worried, you can use an 8V pre-regulator.

One thing you should worry about with a car is that you can get huge
voltage spikes. An RC low-pass filter will help:


Vcar-----[10 ohms]---o--------------------.
+| |+
--- 100uF cap [your thingy]
--- |-
| |
Car Gnd---------------o--------------------'

Or even 7808
.---.
Vcar-----[10]---o--------| |-------.
+| | | |+
--- 100uF '---' [thingy]
--- | |-
| | |
Car Gnd----------o----------o---------'

--

Regards,
Bob Monsen

"Animals, whom we have made our slaves, we do not like to consider our
equal."
-- Charles Darwin

 

[Anthony Fremont]

"Bob Monsen" <rcsurname@comcast.net> wrote in message

Actually, the filter circuit can absorb 100V transients of 100us with
less
than a 1V rise, so it is probably OK. If not, a larger value resistor
will
increase the effectiveness using the standard formula. However, a
zener
won't hurt, and if the transient lasts anywhere near 1ms, will be
required. Also, the reverse polarity protection is a very good idea.

Digikey lists that zener at $1.20, quantity 1, whereas a 1/4W zener +
small power transistor will be 1/2 of that, so using a power
transistor to
help a smaller zener might be cheaper.

Mouser lists the TVS I referenced for $0.56 single quantity, no
transistor needed. Of course a fuse wouldn't be a bad idea for all the
circuits posted thus far.

BTW, must you persist with those anti-creationist quotes in the sig
line? It is just a THEORY after all.

 

[Bob Monsen]

On Sun, 05 Feb 2006 23:54:55 +0000, Anthony Fremont wrote:

"Bob Monsen" <rcsurname@comcast.net> wrote in message
newsan.2006.02.05.22.04.19.634022@comcast.net...
On Sun, 05 Feb 2006 17:18:50 +0000, Anthony Fremont wrote:
BTW, must you persist with those anti-creationist quotes in the sig
line? It is just a THEORY after all.

Despite what critics say, Darwin was a genius, pure and simple. Using

And you personally KNOW this how?



I've read Origin of Species, which is a very careful argument. You might

want to consider doing that too. so you understand at least a little bit
about what you are trying to debunk. Newer sources are probably better,
though. "Darwin's Dangerous Idea" by Daniel C. Dennett gives a good
overview of what scientists believe, and what they don't believe. Dawkins
has written several excellent books on the subject. If you really want to
get into this, you should arm yourself with knowledge. Saying there is 'no
missing link' or 'no new species are created' simply shows your ignorance
of what evidence exists, and what may be problematic.

--
Regards,
Bob Monsen

"We must, however, acknowledge, as it seems to me, that man with all
his noble qualities... still bears in his bodily frame the indelible
stamp of his lowly origin."
-- Charles Darwin

 

[John Fields]

On Sun, 05 Feb 2006 08:49:22 -0800, Bob Monsen
<rcsurname@comcast.net> wrote:

On Sun, 05 Feb 2006 05:23:52 -0600, John Fields wrote:

7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+

Actually, the filter circuit can absorb 100V transients of 100us with less
than a 1V rise, so it is probably OK. If not, a larger value resistor will
increase the effectiveness using the standard formula. However, a zener
won't hurt, and if the transient lasts anywhere near 1ms, will be
required. Also, the reverse polarity protection is a very good idea.

Digikey lists that zener at $1.20, quantity 1, whereas a 1/4W zener +
small power transistor will be 1/2 of that, so using a power transistor to
help a smaller zener might be cheaper.

I like it!

Like this?
7808
+-------+
+12V>----+---[1N4002>]--+-----+-----+----|IN OUT|---+--+8V
| |K | | | GND | |
|K [1N4746] | | +---+---+ |
[1N4002] | C | | [0.1]
| +---B [1000ľF] | |
| E |25V | |
| | | | |
GND>-----+--------------------+-----+--------+-------+

Turns out the Diodes, Inc. half-watters and one-watters are the same
price, and they don't even list a quarter-watter with Digi-Key so I
just went with the one-watter,


--
John Fields
Professional Circuit Designer

 

[Rich Grise]

On Sun, 05 Feb 2006 07:58:57 -0600, John Fields wrote:

On Sun, 05 Feb 2006 12:24:34 GMT, "Anthony Fremont" <spam@anywhere.com
wrote:


"John Fields" <jfields@austininstruments.com> wrote in message

Even better:
7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+

With no current limiting, that'll be a bit rough on that Zener, won't it?

---
Depends on how much current the transient can pump through the Zener, and
for how long the transient lasts.

Sure, some current limiting wouldn't hurt, but the OP told us nothing
about what his load looks like, ---

How about this instead:
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=304881

---
They're essentially the same thing, 5 watt Zener diodes. Here's the data
sheet for the 1N5355:

http://www.onsemi.com/pub/Collateral/1N5333B-D.PDF

Note that it'll do 180 watts for 8.6ms, while the ST device claims 1000
watts for somewhere between 10 and 1000ľs.

Multiply 180 watts by 8.6ms to make apples equal to apples and you get
1548 watts for the Motorola part!

Or, just use a real Transzorb. I'd still put a hash choke between the
VBatt and the junction of the two diodes.

Cheers!
Rich

 

[John Fields]

On Fri, 10 Feb 2006 02:48:13 GMT, Rich Grise <richgrise@example.net>
wrote:

On Sun, 05 Feb 2006 07:58:57 -0600, John Fields wrote:

On Sun, 05 Feb 2006 12:24:34 GMT, "Anthony Fremont" <spam@anywhere.com
wrote:


"John Fields" <jfields@austininstruments.com> wrote in message

Even better:
7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+

With no current limiting, that'll be a bit rough on that Zener, won't it?

---
Depends on how much current the transient can pump through the Zener, and
for how long the transient lasts.

Sure, some current limiting wouldn't hurt, but the OP told us nothing
about what his load looks like, ---

How about this instead:
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=304881

---
They're essentially the same thing, 5 watt Zener diodes. Here's the data
sheet for the 1N5355:

http://www.onsemi.com/pub/Collateral/1N5333B-D.PDF

Note that it'll do 180 watts for 8.6ms, while the ST device claims 1000
watts for somewhere between 10 and 1000ľs.

Multiply 180 watts by 8.6ms to make apples equal to apples and you get
1548 watts for the Motorola part!

Or, just use a real Transzorb.

---
You'd still be using a Zener.
---

I'd still put a hash choke between the
VBatt and the junction of the two diodes.

I thought you liked hash...

--
John Fields
Professional Circuit Designer

 

[Henry]

"Anthony Fremont" <spam@anywhere.com> wrote in message
news:jfwFf.29051$Vr.3320@tornado.texas.rr.com...

"Bob Monsen" <rcsurname@comcast.net> wrote in message
newsan.2006.02.05.22.04.19.634022@comcast.net...
On Sun, 05 Feb 2006 17:18:50 +0000, Anthony Fremont wrote:
BTW, must you persist with those anti-creationist quotes in the sig
line? It is just a THEORY after all.

Despite what critics say, Darwin was a genius, pure and simple. Using

And you personally KNOW this how?

years of original research, he cracked a nut that people had been
trying
to crack for thousands of years, and did it with an elegant,
intuitively
obvious scheme.

I'm afraid that may be more your opinion than an actual fact. Seems to
me that evidence indicates that the nut is still a wee bit short of
being cracked.

These are all quotes from the man himself, not
'anti-creationist' quotes.

I know they are, but the ones you choose to post (aside from the one
here) seem to mostly be anti-creationist. I can't help but believe that
is intentional on your part. Are you trying to make some kind of
statement, or just surreptitiously preaching your brand of "religion" to
the world?

Seriously, I'd put allot more stock in Darwin's theories if they were
backed by a bit more hard evidence. In the 150 years since Darwin,
there has still not been one fossil found representing the so-called
missing link. Can you point me to something resembling proof of at
least one new species having evolved? It's a fact that scores
(depending upon whom you believe) of species become extinct every day,
and AFAICT there have been no new ones forming to take their place.
Certainly not scores every day or it would seem that would be quite
obvious IMO. I'm not saying this is some kind of proof of God, but it
certainly doesn't appear to be helping Darwin's case either.

The big bang theory is a pretty good theory too, if you can get past
that "tiny" problem of the first fraction of second and how no known
physics can explain what happened. Of course we're also left to wonder
about the blue shifted stars, and the fact that over 90% of the matter
in the universe seems to be hiding.

If you were joking, you need to supply a bit more context for folks to
'get it'. If not, well, I feel sorry for you. Trying to suppress
freedom

Gee Bob, I appreciate the thought but, I don't really need your
sympathy. You seem to be saying that belief in God is equivalent to
ignorance, is that about right?

of speech is, while apparently OK with the current US administration,
considered rude and obnoxious by most people. Do you shout down people
who

Oh...so now I'm trying to suppress freedom of speech, geez. If you
don't want a response to your sig lines, then you probably should think
about that.

you disagree with in person, like that narcissistic bully Bill
O'Reilly?

Er, um no, and how did O'Reilly come into this? At any rate, I don't
recall "shouting down" anyone, but some might think you are doing that
right now by putting many more words into my mouth than I said.

Do you support arresting people wearing tee-shirts that you disagree
with?

Oh man, you really are taking this way too seriously. You're only about
one step away from invoking Godwin already.

Oh, and how fast is that TVS? Will it kill all automotive transients
above
30V?

I'm no expert, but it's probably a pretty safe bet to say that it will
not "kill ALL automotive transients above 30V".

One thing that gets confused is that the word "theory" means something
different in science than it does in popular culture. In popular use,
"theory" refers to a mere notion or idea. In science a theory is the highest
level that a model of how-things-work can attain. It stays there until
disproven or replaced by a better theory.

And yes, the big bang theory is under revision as well. It may have to be
replaced. Many ideas have been proposed to explain new data and observations
that dont fit the previous model that was given the status of theory with
what was known then. Even my college Astronomy text from 25 years ago lacks
many discoveries that have been made since. And I am talking about even in
our own solar system with the Kuiper Belt, Oort cloud, moons of gas giants,
NEOs, etc.

Just as Newton had his theories revised and expanded by Einstein, Darwin's
work will, and is, undergoing the same.

Sorry that I dont have anything to add to the electronics part of the
thread.

Henry

 

[John Fields]

On Wed, 22 Feb 2006 20:14:11 -0500, "Henry" <henrytj@pghmail.com>
wrote:

One thing that gets confused is that the word "theory" means something
different in science than it does in popular culture. In popular use,
"theory" refers to a mere notion or idea. In science a theory is the highest
level that a model of how-things-work can attain. It stays there until
disproven or replaced by a better theory.

And yes, the big bang theory is under revision as well. It may have to be
replaced. Many ideas have been proposed to explain new data and observations
that dont fit the previous model that was given the status of theory with
what was known then. Even my college Astronomy text from 25 years ago lacks
many discoveries that have been made since.

---
I guess that's all that can be expected from a text that can't
update itself...
---

And I am talking about even in
our own solar system with the Kuiper Belt, Oort cloud, moons of gas giants,
NEOs, etc.

Just as Newton had his theories revised and expanded by Einstein, Darwin's
work will, and is, undergoing the same.

Sorry that I dont have anything to add to the electronics part of the
thread.

---
Oh well, you got to say what you wanted to anyway.

--
John Fields
Professional Circuit Designer

 

[John Fields]

On Sat, 04 Feb 2006 22:36:18 -0800, Bob Monsen
<rcsurname@comcast.net> wrote:

One thing you should worry about with a car is that you can get huge
voltage spikes. An RC low-pass filter will help:


Vcar-----[10 ohms]---o--------------------.
+| |+
--- 100uF cap [your thingy]
--- |-
| |
Car Gnd---------------o--------------------'

Or even 7808
.---.
Vcar-----[10]---o--------| |-------.
+| | | |+
--- 100uF '---' [thingy]
--- | |-
| | |
Car Gnd----------o----------o---------'

---
Even better:
7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+


--
John Fields
Professional Circuit Designer

 

[Anthony Fremont]

"John Fields" <jfields@austininstruments.com> wrote in message

Even better:
7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+

With no current limiting, that'll be a bit rough on that Zener, won't
it? How about this instead:
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=304881

Here is the datasheet for these amazing devices:
http://www.st.com/stonline/books/pdf/docs/2913.pdf

 

[John Fields]

On Sun, 05 Feb 2006 12:24:34 GMT, "Anthony Fremont"
<spam@anywhere.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message

Even better:
7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+

With no current limiting, that'll be a bit rough on that Zener, won't
it?

---
Depends on how much current the transient can pump through the
Zener, and for how long the transient lasts.

Sure, some current limiting wouldn't hurt, but the OP told us
nothing about what his load looks like,
---

How about this instead:

http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=304881

---
They're essentially the same thing, 5 watt Zener diodes. Here's the
data sheet for the 1N5355:

http://www.onsemi.com/pub/Collateral/1N5333B-D.PDF

Note that it'll do 180 watts for 8.6ms, while the ST device claims
1000 watts for somewhere between 10 and 1000ľs.

Multiply 180 watts by 8.6ms to make apples equal to apples and you
get 1548 watts for the Motorola part!


--
John Fields
Professional Circuit Designer

 

[Bob Monsen]

On Sun, 05 Feb 2006 05:23:52 -0600, John Fields wrote:

On Sat, 04 Feb 2006 22:36:18 -0800, Bob Monsen
rcsurname@comcast.net> wrote:


One thing you should worry about with a car is that you can get huge
voltage spikes. An RC low-pass filter will help:


Vcar-----[10 ohms]---o--------------------.
+| |+
--- 100uF cap [your thingy]
--- |-
| |
Car Gnd---------------o--------------------'

Or even 7808
.---.
Vcar-----[10]---o--------| |-------.
+| | | |+
--- 100uF '---' [thingy]
--- | |-
| | |
Car Gnd----------o----------o---------'

---
Even better:
7808
+-------+
+12V>----+---[1N4002>]--+--------+------|IN OUT|---+--+8V
|K |K |+ | GND | |
[1N4002] [1N5355] [1000ľF] +---+---+ [0.1]
| | |25V | |
GND>-----+--------------+--------+----------+-------+

Actually, the filter circuit can absorb 100V transients of 100us with less
than a 1V rise, so it is probably OK. If not, a larger value resistor will
increase the effectiveness using the standard formula. However, a zener
won't hurt, and if the transient lasts anywhere near 1ms, will be
required. Also, the reverse polarity protection is a very good idea.

Digikey lists that zener at $1.20, quantity 1, whereas a 1/4W zener +
small power transistor will be 1/2 of that, so using a power transistor to
help a smaller zener might be cheaper.

--
Regards,
Bob Monsen

" We can allow satellites, planets, suns, universe, nay whole systems
of universes, to be governed by laws, but the smallest insect, we wish
to be created at once by special act."
-- Charles Darwin

 

[JeffM]

must you persist with those anti-creationist quotes in the sig line?
It is just a THEORY after all.
Anthony Fremont

I didn't see a smilie, so I assume that you're serious.

For those who failed 5th grade science,
here's the problem with offering Creationism as a "theory":
A theory has to be falsifiable; religious dogma is not falsifiable
and is therefore not a theory and is not Science.
http://72.14.207.104/search?q=cache:RuavNLqg-B4Jhyun5.ucr.edu/~wudka/Physics7/Notes_www/node6.html+falsifiable+theory-must-be-*-*-falsifiable+What-is-the-*-*-scientific-method

By a similar definition,
this kind of unprovable silliness is also not "Philosophy".
In the 21st Century, the only use for these fables
is in a discussion of humans' capacity for making up superstitious
nonsense
to attempt to explain what they don't yet understand
--and examining how so many cling to these old wives's tales
long after explanations are offered which are far more probable.

"I think that naming your ignorance 'God' and pretending that,
having named it, you have converted ignorance to knowledge
is a sorry approach to the unknown."
--John Popelish, alt.atheism 12/24/1999

 

[Bob Monsen]

On Sun, 05 Feb 2006 17:18:50 +0000, Anthony Fremont wrote:

BTW, must you persist with those anti-creationist quotes in the sig
line? It is just a THEORY after all.

Despite what critics say, Darwin was a genius, pure and simple. Using
years of original research, he cracked a nut that people had been trying
to crack for thousands of years, and did it with an elegant, intuitively
obvious scheme. These are all quotes from the man himself, not
'anti-creationist' quotes.

If you were joking, you need to supply a bit more context for folks to
'get it'. If not, well, I feel sorry for you. Trying to suppress freedom
of speech is, while apparently OK with the current US administration,
considered rude and obnoxious by most people. Do you shout down people who
you disagree with in person, like that narcissistic bully Bill O'Reilly?
Do you support arresting people wearing tee-shirts that you disagree
with?

Oh, and how fast is that TVS? Will it kill all automotive transients above
30V?

--
Regards,
Bob Monsen

" As for a future life, every man must judge for himself between
conflicting vague probabilities."
-- Charles Darwin

 

[JeffM]

Despite what critics say, Darwin was a genius, pure and simple.
Bob Monsen

If you missed the installment of Charlie Rose
where James Watson and Edward O. Wilson talked about Darwin
(each having written a book about him), here's the high point:
http://72.14.207.104/search?q=cache:K272hq1DlPUJ:boards.charlierose.com/board/pst.asp?m=tq%26ti=15673%26fi=24+wilson+watson+*-*-*-greatest-man-in-*-history-*-*-*

 

[Anthony Fremont]

"Bob Monsen" <rcsurname@comcast.net> wrote in message
newsan.2006.02.05.22.04.19.634022@comcast.net...

On Sun, 05 Feb 2006 17:18:50 +0000, Anthony Fremont wrote:
BTW, must you persist with those anti-creationist quotes in the sig
line? It is just a THEORY after all.

Despite what critics say, Darwin was a genius, pure and simple. Using

And you personally KNOW this how?

years of original research, he cracked a nut that people had been
trying
to crack for thousands of years, and did it with an elegant,
intuitively
obvious scheme.

I'm afraid that may be more your opinion than an actual fact. Seems to
me that evidence indicates that the nut is still a wee bit short of
being cracked.

These are all quotes from the man himself, not
'anti-creationist' quotes.

I know they are, but the ones you choose to post (aside from the one
here) seem to mostly be anti-creationist. I can't help but believe that
is intentional on your part. Are you trying to make some kind of
statement, or just surreptitiously preaching your brand of "religion" to
the world?

Seriously, I'd put allot more stock in Darwin's theories if they were
backed by a bit more hard evidence. In the 150 years since Darwin,
there has still not been one fossil found representing the so-called
missing link. Can you point me to something resembling proof of at
least one new species having evolved? It's a fact that scores
(depending upon whom you believe) of species become extinct every day,
and AFAICT there have been no new ones forming to take their place.
Certainly not scores every day or it would seem that would be quite
obvious IMO. I'm not saying this is some kind of proof of God, but it
certainly doesn't appear to be helping Darwin's case either.

The big bang theory is a pretty good theory too, if you can get past
that "tiny" problem of the first fraction of second and how no known
physics can explain what happened. Of course we're also left to wonder
about the blue shifted stars, and the fact that over 90% of the matter
in the universe seems to be hiding.

If you were joking, you need to supply a bit more context for folks to
'get it'. If not, well, I feel sorry for you. Trying to suppress
freedom

Gee Bob, I appreciate the thought but, I don't really need your
sympathy. You seem to be saying that belief in God is equivalent to
ignorance, is that about right?

of speech is, while apparently OK with the current US administration,
considered rude and obnoxious by most people. Do you shout down people
who

Oh...so now I'm trying to suppress freedom of speech, geez. If you
don't want a response to your sig lines, then you probably should think
about that.

you disagree with in person, like that narcissistic bully Bill
O'Reilly?

Er, um no, and how did O'Reilly come into this? At any rate, I don't
recall "shouting down" anyone, but some might think you are doing that
right now by putting many more words into my mouth than I said.

Do you support arresting people wearing tee-shirts that you disagree
with?

Oh man, you really are taking this way too seriously. You're only about
one step away from invoking Godwin already.

Oh, and how fast is that TVS? Will it kill all automotive transients
above
30V?

I'm no expert, but it's probably a pretty safe bet to say that it will
not "kill ALL automotive transients above 30V".

 

[Bob Monsen]

On Sun, 05 Feb 2006 14:27:06 -0800, JeffM wrote:

Despite what critics say, Darwin was a genius, pure and simple.
Bob Monsen

If you missed the installment of Charlie Rose
where James Watson and Edward O. Wilson talked about Darwin
(each having written a book about him), here's the high point:
http://72.14.207.104/search?q=cache:K272hq1DlPUJ:boards.charlierose.com/board/pst.asp?m=tq%26ti=15673%26fi=24+wilson+watson+*-*-*-greatest-man-in-*-history-*-*-*

Well, they are biologists. He was the man, though. He waited 20 YEARS to
publish, so he could get his ducks in a line. Every t was crossed, every i
was dotted. The people who claim Natural Selection is 'an unproven theory'
simply haven't read him.

--
Regards,
Bob Monsen

"We must, however, acknowledge, as it seems to me, that man with all
his noble qualities... still bears in his bodily frame the indelible
stamp of his lowly origin."
-- Charles Darwin

 

[Bob Monsen]

On Mon, 06 Feb 2006 07:27:56 -0600, John Fields wrote:
7808

+-------+
+12V>----+---[1N4002>]--+-----+-----+----|IN OUT|---+--+8V
| |K | | | GND | |
|K [1N4746] | | +---+---+ |
[1N4002] | C | | [0.1]
| +---B [1000ľF] | |
| E |25V | |
| | | | |
GND>-----+--------------------+-----+--------+-------+

Turns out the Diodes, Inc. half-watters and one-watters are the same
price, and they don't even list a quarter-watter with Digi-Key so I
just went with the one-watter,

Looks great!. It can be very small, and will cost him next to nothing to
build...

--
Regards,
Bob Monsen

"False facts are highly injurious to the progress of science, for they
often endure long; but false views, if supported by some evidence, do
little harm, for every one takes a salutary pleasure in proving their
falseness."
-- Charles Darwin