Power regulation.

[Colin Dawson]

Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to support a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd like to
overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com

 

[Mook Johnson]

LM2587-adj

www.national.com

Use feedback resistors to change the output voltage.



"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...

Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to support a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd like to
overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com

 

[John Larkin]

On Sat, 30 Apr 2005 14:48:30 GMT, "Mook Johnson" <mook@mook.net>
wrote:

look a little closer. the -adj version will do 18 volts output at 2 amps.

Not with 12 volts in!

John

 

[Rich Grise]

On Sat, 30 Apr 2005 14:16:47 +0000, Colin Dawson wrote:

Not bad, but I'm looking to get 12,13.8 & 15 volts as a minimum. Looking
at the Datasheet, the LM2587 will only give 12 volt max, which is short of
the 18v ideal and 15v that I actually need.

To explain a little further, the regulator will be used to provide a clean
constant power supply to a computerised telescope. I'm looking to
overengineer, this part of a larger project, so that it will be easy to use
the design on other scopes. My telescope works on a voltage between 12 and
15 volts. But it works best on 15v.

What exactly does "works best" mean? What does this telescope actually
do that cares whether the voltage is at the low or high end of the spec?

The cleanest DC you'll get is right from the battery.

Thanks,
Rich

 

[Genome]

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:jrMce.3491$Cq2.1998@fe2.news.blueyonder.co.uk...

Not bad, but I'm looking to get 12,13.8 & 15 volts as a minimum. Looking
at the Datasheet, the LM2587 will only give 12 volt max, which is short of
the 18v ideal and 15v that I actually need.

To explain a little further, the regulator will be used to provide a clean
constant power supply to a computerised telescope. I'm looking to
overengineer, this part of a larger project, so that it will be easy to
use
the design on other scopes. My telescope works on a voltage between 12
and
15 volts. But it works best on 15v. I don't know why the manufacturer's
didn't bother, but the scope doesn't regulate it's own power... One
simple
solution to this is to use a dedicated battery for the scope, but even
then
it's only producing 12V, from research, different makes and models of
telescope have different power requirements. My Telescope works best on
15v, the next model up prefers 18v, the next model down from mine needs
12v.
Some other brands of scope prefer 13.8V. Ideally the regulator circuit
will be able to turn an unregulated battery supply into a very stable
supply, which will help to improve the ability of the scope to track and
slew with high precision, it's good now, but I think this will help to
make
it even better. This is important as I'm basically trying to get the
scope to move as smoothly as possible so that it can track moving objects
accuratly for hours at a time.

Regards

Colin.

"Mook Johnson" <mook@mook.net> wrote in message
news:MwKce.31564$AE6.923@tornado.texas.rr.com...
LM2587-adj

www.national.com

Use feedback resistors to change the output voltage.



"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to
support
a continuous 2A, at 15V. Instead of making a fixed regulator, I'd
like
to overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com

Fucking bunch of top posters.

Meneeeee arp weeble blib a plingy doofle narf nerrrrrr.

Eeeeh when I wert lad and reached the legal beer drinking age we'd go out of
a Friday night down the Magnet Tavern and I'd get pissed.

There was one night we crept back into school and came across the astronomy
club in the quadrangle. Nice eight inch reflector on a tall pole ground and
built by members of long ago.

Lot's of sprogs, a step ladder, plus the Physics master about.

People are looking bored.

Much muttering amongst my mates that they should keep me away from things.

So, they pick the bright one... always a good guess, and phaff about trying
to find it. Which they don't, could have something to do with the viewfinder
being shit.

I get bored and butt in.

Grab the telescope and, using the metal work (it's quality stuff), line
things up on where the bright thing is. Hop up the ladder and.... it's
Jupiter.... but it's moving fast.

Re-align things and boost a sprog up the ladder.

Jupiter buggers off.

Do it again.

Next sprog.

And so on.

Coooooooooo!

DNA

 

[Jonathan Westhues]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:53a771dhan9m8ctc52729vm6svgia76lnn@4ax.com...

Have a look at national-semi's 'simple switchers' and their
counterparts.
This is fairly straight forward stuff..
A discontinuous flyback is the easiest for your job.


But he needs Vout to go both above and below Vin.

Isn't that why he said flyback?

Though 2A might be a bit much for the "simple switcher" parts.

Jonathan
http://cq.cx/

 

[Brian]

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...

Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to support
a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd like
to
overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com

How about using a MC34063A, in the up/down circuit configuration? Take a
look at http://www.fncwired.com/12-18VoltEx/

Regards,

Brian

 

[Colin Dawson]

"Brian" <bellis350@comcast.net> wrote in message
news:xuqdnbG2Pby-T-7fRVn-2g@comcast.com...

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to
support a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd like
to
overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com



How about using a MC34063A, in the up/down circuit configuration? Take a
look at http://www.fncwired.com/12-18VoltEx/

Regards,

Brian

Thanks all.

This one looks like it's perfect for the job. When designing the circuit, I
can put the output voltage resisters into the circuit then use a jumper to
select the desired voltage.

Would I be right in assuming that this circuit is capable of delivering 16A?
Looking at the datasheets, D2 looks to be rated for 16A continuous, and Q is
rated at 80A. Mind you there's an inductor in the circuit, and I've got no
idea what effect that will have.

Colin Dawson

 

[Colin Dawson]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.04.30.16.33.21.196883@example.net...

On Sat, 30 Apr 2005 14:16:47 +0000, Colin Dawson wrote:

Not bad, but I'm looking to get 12,13.8 & 15 volts as a minimum.
Looking
at the Datasheet, the LM2587 will only give 12 volt max, which is short
of
the 18v ideal and 15v that I actually need.

To explain a little further, the regulator will be used to provide a
clean
constant power supply to a computerised telescope. I'm looking to
overengineer, this part of a larger project, so that it will be easy to
use
the design on other scopes. My telescope works on a voltage between 12
and
15 volts. But it works best on 15v.

What exactly does "works best" mean? What does this telescope actually
do that cares whether the voltage is at the low or high end of the spec?

The cleanest DC you'll get is right from the battery.

Thanks,
Rich

Hehe, I wish that was true. As I've already said, I'm also running other
devices from the same battery, even though they're in parrallel, the changes
in voltage of the battery effects the electronics in the telescopes
circuitry.

The scope has to use timing mechanisms to control geared motors so that the
scope drives at sidereal rates. In short the scope moves clockwise at half
the speed of the hourhand on a clock. I use the scope for
astrophotography, and in order to take a photo of a deep sky object (galaxy
for example) the scope needs to track the object smoothly, and accuractly
for the entire length time that the camera shutter is open. This time can
range from about 5 mins to over an hour! In that time, any glitchs in the
tracking will show up in the photo. There's are alot of mechanical things
that I'm already aware of which affect the tracking. To make matters worse,
the timing circuits seem to be affected by changes in voltage, this is most
obviously seen when at the start of a session the scope with track
perfectly, then as the night wears on, and the voltage on the battery drops
the tracking will get gradually less accurate. Some of the other things
that I run from the same battery (Laptop and Dew heater) pull alot of
current, and whilst they're pulling the high current the scope gets less
power and it's timing circuits do not work quite as well. I'm not sure of
all the whys and wherefores about this, but for my telescope 15V has been
found to be the best voltage to run the scope on. The reason why I was
asking about getting the circuit to deliver other voltages is that other
makes and models of telescope work best at other prescribed voltages, again
these scopes do benefit from regulated power supplies.

It's not that the manufacturer's forgot about power regulation. Their answer
is to buy their power adapters, the mains adapters are regulated in teh
adapter. Some of the 12v external power kits are regulated, but most are
simple leads which plug into the scope and a cigar lighter socket on a car,
and are not regulated (although some are).

Regards

Colin Dawson

 

[Colin Dawson]

"Genome" <ilike_spam@yahoo.co.uk> wrote in message
news:MrOce.11111$5A3.1082@newsfe4-win.ntli.net...

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:jrMce.3491$Cq2.1998@fe2.news.blueyonder.co.uk...
Not bad, but I'm looking to get 12,13.8 & 15 volts as a minimum.
Looking
at the Datasheet, the LM2587 will only give 12 volt max, which is short
of
the 18v ideal and 15v that I actually need.

To explain a little further, the regulator will be used to provide a
clean
constant power supply to a computerised telescope. I'm looking to
overengineer, this part of a larger project, so that it will be easy to
use
the design on other scopes. My telescope works on a voltage between 12
and
15 volts. But it works best on 15v. I don't know why the manufacturer's
didn't bother, but the scope doesn't regulate it's own power... One
simple
solution to this is to use a dedicated battery for the scope, but even
then
it's only producing 12V, from research, different makes and models of
telescope have different power requirements. My Telescope works best on
15v, the next model up prefers 18v, the next model down from mine needs
12v.
Some other brands of scope prefer 13.8V. Ideally the regulator circuit
will be able to turn an unregulated battery supply into a very stable
supply, which will help to improve the ability of the scope to track and
slew with high precision, it's good now, but I think this will help to
make
it even better. This is important as I'm basically trying to get the
scope to move as smoothly as possible so that it can track moving objects
accuratly for hours at a time.

Regards

Colin.

"Mook Johnson" <mook@mook.net> wrote in message
news:MwKce.31564$AE6.923@tornado.texas.rr.com...
LM2587-adj

www.national.com

Use feedback resistors to change the output voltage.



"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a
variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to
support
a continuous 2A, at 15V. Instead of making a fixed regulator, I'd
like
to overengineer it so that it is switchable between 12v, 13.8v, 15v
and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com






Fucking bunch of top posters.

Meneeeee arp weeble blib a plingy doofle narf nerrrrrr.

Eeeeh when I wert lad and reached the legal beer drinking age we'd go out
of
a Friday night down the Magnet Tavern and I'd get pissed.

There was one night we crept back into school and came across the
astronomy
club in the quadrangle. Nice eight inch reflector on a tall pole ground
and
built by members of long ago.

Lot's of sprogs, a step ladder, plus the Physics master about.

People are looking bored.

Much muttering amongst my mates that they should keep me away from things.

So, they pick the bright one... always a good guess, and phaff about
trying
to find it. Which they don't, could have something to do with the
viewfinder
being shit.

I get bored and butt in.

Grab the telescope and, using the metal work (it's quality stuff), line
things up on where the bright thing is. Hop up the ladder and.... it's
Jupiter.... but it's moving fast.

Re-align things and boost a sprog up the ladder.

Jupiter buggers off.

Do it again.

Next sprog.

And so on.

Coooooooooo!

DNA

LOL.

Yep, things have moved on a little since then. My scope is driven so you
just line it up and the object stays in the eyepiece.

Juptier, easy, it's the brightest star in the sky (barring the sun and
moon). Saturn comes next (but not at the moment, you'll need to wait til
next year now).

Don't get me wrong, the scope works brilliantly, and the best bit is showing
someone something that's right above their head that, not only they didn't
know was there, but simply takes their breath away and opens their mind to
the countless posibilities that exist. Damm, I hate it when I start getting
all philisophical.

Regards

Colin Dawson

 

[John Woodgate]

I read in sci.electronics.design that Colin Dawson
<newsgroups@cjdawson.com> wrote (in
<NSRce.9441$j54.5905@fe3.news.blueyonder.co.uk&gt about 'Power
regulation.', on Sat, 30 Apr 2005:

Juptier, easy, it's the brightest star in the sky (barring the sun and
moon). Saturn comes next (but not at the moment, you'll need to wait
til next year now).

What have you got against Venus? Beats Jupiter by quite a bit.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Mook Johnson]

Sure it can as a flyback regulator.

I've done 30 volts of a flyback with it! no sweat.


"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:e0a771tv2n7sn1oql5b5jl9lfb221kfndg@4ax.com...

On Sat, 30 Apr 2005 14:48:30 GMT, "Mook Johnson" <mook@mook.net
wrote:

look a little closer. the -adj version will do 18 volts output at 2 amps.

Not with 12 volts in!

John

 

[Brian]

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:0gRce.8960$j54.7214@fe3.news.blueyonder.co.uk...

"Brian" <bellis350@comcast.net> wrote in message
news:xuqdnbG2Pby-T-7fRVn-2g@comcast.com...

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as
straight
forwards as I first thought. Basically, I'm looking to have a
variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to
support a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd
like
to
overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com



How about using a MC34063A, in the up/down circuit configuration? Take
a
look at http://www.fncwired.com/12-18VoltEx/

Regards,

Brian




Thanks all.

This one looks like it's perfect for the job. When designing the
circuit, I
can put the output voltage resisters into the circuit then use a jumper
to
select the desired voltage.

Would I be right in assuming that this circuit is capable of delivering
16A?
Looking at the datasheets, D2 looks to be rated for 16A continuous, and
Q is
rated at 80A. Mind you there's an inductor in the circuit, and I've
got no
idea what effect that will have.

Colin Dawson

This circuit is only capable of delivering 2A out, continuis. For more
amperage out, the inductor and resistor Rsc would need to be smaller. The
high amperage ratings of the components, is for a lower loss across them
(for more effeciency). If you want to know more about the selection of the
components (for a higher amperage output), get the data sheet for the
MC34063A.

Brian

 

[Colin Dawson]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:q6i+Gwk1Y$cCFwlt@jmwa.demon.co.uk...

I read in sci.electronics.design that Colin Dawson
newsgroups@cjdawson.com> wrote (in
NSRce.9441$j54.5905@fe3.news.blueyonder.co.uk&gt about 'Power regulation.',
on Sat, 30 Apr 2005:

Juptier, easy, it's the brightest star in the sky (barring the sun and
moon). Saturn comes next (but not at the moment, you'll need to wait til
next year now).

What have you got against Venus? Beats Jupiter by quite a bit.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I got's nothing against it as such, just don't tend to think about Venus, as
it's not normally on my list of objects to target. At the moment, I've
simply waiting for a single clear night so that I can get 1/2 a chance to
image Jupiter. So far, I've not had a single chance all year!

Colin Dawson.

 

[Colin Dawson]

"Brian" <bellis350@comcast.net> wrote in message
news:gvGdnRcH3oRgYu7fRVn-qg@comcast.com...

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:0gRce.8960$j54.7214@fe3.news.blueyonder.co.uk...

"Brian" <bellis350@comcast.net> wrote in message
news:xuqdnbG2Pby-T-7fRVn-2g@comcast.com...

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as
straight
forwards as I first thought. Basically, I'm looking to have a
variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to
support a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd
like
to
overengineer it so that it is switchable between 12v, 13.8v, 15v
and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com



How about using a MC34063A, in the up/down circuit configuration?
Take a
look at http://www.fncwired.com/12-18VoltEx/

Regards,

Brian




Thanks all.

This one looks like it's perfect for the job. When designing the
circuit, I
can put the output voltage resisters into the circuit then use a jumper
to
select the desired voltage.

Would I be right in assuming that this circuit is capable of delivering
16A?
Looking at the datasheets, D2 looks to be rated for 16A continuous, and
Q is
rated at 80A. Mind you there's an inductor in the circuit, and I've
got no
idea what effect that will have.

Colin Dawson



This circuit is only capable of delivering 2A out, continuis. For more
amperage out, the inductor and resistor Rsc would need to be smaller. The
high amperage ratings of the components, is for a lower loss across them
(for more effeciency). If you want to know more about the selection of the
components (for a higher amperage output), get the data sheet for the
MC34063A.

Brian

Ah, thanks for the explaination. I figured that there was more to this than
meets the eye. Actually 2 Amp for this supply is perfect, as my scope has a
2A quick blow fuse which has never blown (and isn't likely too either). In
fact the scope only pulls about 1.6A when slewing at high speed in both Alt
and Az (that's two stepper motor circuits at full speed).

Regards

Colin Dawson.

 

[Brian]

">> > Thanks all.

This one looks like it's perfect for the job. When designing the
circuit, I
can put the output voltage resisters into the circuit then use a
jumper
to
select the desired voltage.

Would I be right in assuming that this circuit is capable of
delivering
16A?
Looking at the datasheets, D2 looks to be rated for 16A continuous,
and
Q is
rated at 80A. Mind you there's an inductor in the circuit, and
I've
got no
idea what effect that will have.

Colin Dawson



This circuit is only capable of delivering 2A out, continuis. For more
amperage out, the inductor and resistor Rsc would need to be smaller.
The
high amperage ratings of the components, is for a lower loss across
them
(for more effeciency). If you want to know more about the selection of
the
components (for a higher amperage output), get the data sheet for the
MC34063A.

Brian



Ah, thanks for the explaination. I figured that there was more to this
than
meets the eye. Actually 2 Amp for this supply is perfect, as my scope
has a
2A quick blow fuse which has never blown (and isn't likely too either).
In
fact the scope only pulls about 1.6A when slewing at high speed in both
Alt
and Az (that's two stepper motor circuits at full speed).

Regards

Colin Dawson.

When you construct this, keep all the component leads as short as
possible. Keep the ground of the MC34063A, seperate from the grounds of the
power components. Run each ground, back to the ground of the input
capacitor.

If you want to wind your own inductor, I would suggest using a toroidal
core (less electrical noise).

Core Mfg. "Magnetics", part number 55201-A2, use 14 guage wire, 16 turns
on core.
or
Core Mfg. "Arnold", part number A-393163=2, use 14 guage wire, 16 turns on
core.

Brian

 

[Rich Grise]

On Sat, 30 Apr 2005 20:16:34 +0000, Colin Dawson wrote:

"Rich Grise" <richgrise@example.net> wrote in message
What exactly does "works best" mean? What does this telescope actually
do that cares whether the voltage is at the low or high end of the spec?

...perfectly, then as the night wears on, and the voltage on the battery
drops the tracking will get gradually less accurate.

Then, since you've asked in an electronics NG, the answer is to repair
your timing mechanism. Or redesign it. You _could_ use a "low-dropout"
regulator, but then you're still dependent on the accuracy of your
voltage regulator. I once saw a thing on teevee where they had an
actual, mechanical, clock movement to track their scopes. BIG scopes. I
saw the balance wheel going "tick tock, tick tock, etc." In other
words, you're asking the wrong question. There are folks here who could
design a scope tracker for you that would beat _anything_ that you could
come up with by just trying to regulate the input voltage.

Heck, use a clock! And a crystal-controlled reference. Practically
nothing to it, and it could run from, say, an eight to, say, eighteen volt
power supply, with probably better than 0.001 percent accuracy! Really!
Just ask Jim Thompson! ;-)

Oh, wait a minute - he's the analog guru here . Digital is SOOOoooo
much easier! (hey, guroids, what's the division factor from 4915200 to
60?)

Good Luck!
Rich
(.001 percent is 100 ppm, right?)

 

[R.Lewis]

"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...

Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to support a
continuous 2A, at 15V. Instead of making a fixed regulator, I'd like to
overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com

13.8 volts is the common figure used for float charging a lead-acid battery.
Boost/float or boost/trickle chargers will produce higher battery voltages
toward the end of the boost phase around 2.35 to 2.4 vpc.

11 volts is a bit high for a low battery cut-off. 1.7vpc (i.e.10.2V in your
case) is considered a practical but conservative voltage cut-off. Many
commercial units go for 1.5 vpc.

Have a look at national-semi's 'simple switchers' and their counterparts.
This is fairly straight forward stuff..
A discontinuous flyback is the easiest for your job.




For ease look at nationals 'simple switcher' parts.

 

[Colin Dawson]

Not bad, but I'm looking to get 12,13.8 & 15 volts as a minimum. Looking
at the Datasheet, the LM2587 will only give 12 volt max, which is short of
the 18v ideal and 15v that I actually need.

To explain a little further, the regulator will be used to provide a clean
constant power supply to a computerised telescope. I'm looking to
overengineer, this part of a larger project, so that it will be easy to use
the design on other scopes. My telescope works on a voltage between 12 and
15 volts. But it works best on 15v. I don't know why the manufacturer's
didn't bother, but the scope doesn't regulate it's own power... One simple
solution to this is to use a dedicated battery for the scope, but even then
it's only producing 12V, from research, different makes and models of
telescope have different power requirements. My Telescope works best on
15v, the next model up prefers 18v, the next model down from mine needs 12v.
Some other brands of scope prefer 13.8V. Ideally the regulator circuit
will be able to turn an unregulated battery supply into a very stable
supply, which will help to improve the ability of the scope to track and
slew with high precision, it's good now, but I think this will help to make
it even better. This is important as I'm basically trying to get the
scope to move as smoothly as possible so that it can track moving objects
accuratly for hours at a time.

Regards

Colin.

"Mook Johnson" <mook@mook.net> wrote in message
news:MwKce.31564$AE6.923@tornado.texas.rr.com...

LM2587-adj

www.national.com

Use feedback resistors to change the output voltage.



"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to support
a continuous 2A, at 15V. Instead of making a fixed regulator, I'd like
to overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com

 

[Mook Johnson]

look a little closer. the -adj version will do 18 volts output at 2 amps.

you can regulate down fron there.

Use Websim to test you design.


"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:jrMce.3491$Cq2.1998@fe2.news.blueyonder.co.uk...

Not bad, but I'm looking to get 12,13.8 & 15 volts as a minimum. Looking
at the Datasheet, the LM2587 will only give 12 volt max, which is short of
the 18v ideal and 15v that I actually need.

To explain a little further, the regulator will be used to provide a clean
constant power supply to a computerised telescope. I'm looking to
overengineer, this part of a larger project, so that it will be easy to
use the design on other scopes. My telescope works on a voltage between
12 and 15 volts. But it works best on 15v. I don't know why the
manufacturer's didn't bother, but the scope doesn't regulate it's own
power... One simple solution to this is to use a dedicated battery for
the scope, but even then it's only producing 12V, from research, different
makes and models of telescope have different power requirements. My
Telescope works best on 15v, the next model up prefers 18v, the next model
down from mine needs 12v. Some other brands of scope prefer 13.8V.
Ideally the regulator circuit will be able to turn an unregulated battery
supply into a very stable supply, which will help to improve the ability
of the scope to track and slew with high precision, it's good now, but I
think this will help to make it even better. This is important as I'm
basically trying to get the scope to move as smoothly as possible so that
it can track moving objects accuratly for hours at a time.

Regards

Colin.

"Mook Johnson" <mook@mook.net> wrote in message
news:MwKce.31564$AE6.923@tornado.texas.rr.com...
LM2587-adj

www.national.com
Use feedback resistors to change the output voltage.



"Colin Dawson" <newsgroups@cjdawson.com> wrote in message
news:H0Jce.7870$j54.5302@fe3.news.blueyonder.co.uk...
Hi all.

I'm looking to build a power regulator. However, it's not as straight
forwards as I first thought. Basically, I'm looking to have a variable
input voltage that ranges between 11v and 13.8v (an 85Ah Lead Acid
battery). The output from the regulator will need to be able to support
a continuous 2A, at 15V. Instead of making a fixed regulator, I'd like
to overengineer it so that it is switchable between 12v, 13.8v, 15v and
possibly 18v (although this can be ommitted).

Can anyone give me some pointers one how to go about doing this.

Regards

Colin Dawson
www.cjdawson.com