In article <405B1310.3AE229AD@yahoo.com>
           spamgoeshere4@yahoo.com "rickman" writes:

> I would suggest taking a look at building your own.  I worked on a board
> where one of the engineers spec'd a hand made choke/transformer.  He
> wrote out assembly instructions and they had an assembler make them. 
> Winding a transformer is not really that hard unless you are trying to
> make it very small.  I know that several of the coil companies sell
> cores.  

I am more fortunate than most at present I suppose. I have reasonable 
access to a coil winding machine. RS Components do a range of small
transformer cores and assemblies that make the task quite easy. With 
1W power requirement you could probably get away with a small ferrite 
ring and wind it by hand (takes an investment of time but for one-off 
or just a few may well be worth such hassle).

Calculating a transformer for a psu is not really that hard. Rough 
and ready calculations can be done on just the turns ration required 
to get the sought voltage step. A PWM driven pair of transistors on 
either leg of a centre tapped primary would act as a suitable input 
chopper and by varying the ON time of each device you can adjust the 
output voltage.

The result may, however, be slightly more expensive in board real-
estate than two of the TRAMCO or BB devices. When it comes to wanting 
five isolated outputs then there is no contest. The self-wound 
transformer wins out in small numbers and I can get production 
quantities wound from the details i have already documented.

-- 
********************************************************************
Paul E. Bennett ....................<email://peb@amleth.demon.co.uk>
Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972 .........NOW AVAILABLE:- HIDECS COURSE......
Tel: +44 (0)1235-811095 .... see http://www.feabhas.com for details.
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

Spehro Pefhany wrote:
> 
> On Fri, 19 Mar 2004 08:38:31 +0100, the renowned "Meindert Sprang"
> <mhsprang@NOcustomSPAMware.nl> wrote:
> 
> >""Paul E. Bennett"" <peb@amleth.demon.co.uk> wrote in message
> >news:1079656094snz@amleth.demon.co.uk...
> >> Alternatively, he could do his own if he can manage to wind his own
> >> transformer. I often need several isolated DC supplies so I just wind
> >> up a transformer with the requisite number of secondaries and configure
> >> a simple chopper to drive it.
> >
> >I agree. But not feasible for regular production, but in quantities that do
> >not justify have a transformer produced for me. That's the reason I was
> >looking for an off-the-shelf product.
> 
> Yes, you have an inconvenient quantity range.

I would suggest taking a look at building your own.  I worked on a board
where one of the engineers spec'd a hand made choke/transformer.  He
wrote out assembly instructions and they had an assembler make them. 
Winding a transformer is not really that hard unless you are trying to
make it very small.  I know that several of the coil companies sell
cores.  

-- 

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design      URL http://www.arius.com
4 King Ave                               301-682-7772 Voice
Frederick, MD 21701-3110                 301-682-7666 FAX

On Fri, 19 Mar 2004 08:38:31 +0100, the renowned "Meindert Sprang"
<mhsprang@NOcustomSPAMware.nl> wrote:

>""Paul E. Bennett"" <peb@amleth.demon.co.uk> wrote in message
>news:1079656094snz@amleth.demon.co.uk...
>> Alternatively, he could do his own if he can manage to wind his own
>> transformer. I often need several isolated DC supplies so I just wind
>> up a transformer with the requisite number of secondaries and configure
>> a simple chopper to drive it.
>
>I agree. But not feasible for regular production, but in quantities that do
>not justify have a transformer produced for me. That's the reason I was
>looking for an off-the-shelf product.

Yes, you have an inconvenient quantity range. 

>What strikes me most is that I think there are a lot of products or
>equipment in the market that could use a wide-intput converter (8-30V) and
>have two isolated outputs. About every Modbus, Profibus or whateverBus
>device could use such a converter. Therefore I am surpised it does not exist
>as low power/low cost mass production product.

Unfortunately, those are all rather low-volume process control
applications. Thus, the function is available, just not so cheap and
not so available. 

Best regards, 
Spehro Pefhany
-- 
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

""Paul E. Bennett"" <peb@amleth.demon.co.uk> wrote in message
news:1079656094snz@amleth.demon.co.uk...
> Alternatively, he could do his own if he can manage to wind his own
> transformer. I often need several isolated DC supplies so I just wind
> up a transformer with the requisite number of secondaries and configure
> a simple chopper to drive it.

I agree. But not feasible for regular production, but in quantities that do
not justify have a transformer produced for me. That's the reason I was
looking for an off-the-shelf product.

What strikes me most is that I think there are a lot of products or
equipment in the market that could use a wide-intput converter (8-30V) and
have two isolated outputs. About every Modbus, Profibus or whateverBus
device could use such a converter. Therefore I am surpised it does not exist
as low power/low cost mass production product.

Meindert

In article <4059E95B.66F19FDE@yahoo.com>
           spamgoeshere4@yahoo.com "rickman" writes:

> Meindert Sprang wrote:
> > 
> > "Bobsprit" <Bobsprit@aol.com> wrote in message
> > news:bxi6c.11301$E8.2842421@news4.srv.hcvlny.cv.net...
> > > ,the dual output is not what I want. Most dual-output types ar +/-
> > > > outputs. I need two independent 5V outputs, isolated from eachother too.
> > > So
> > > > far, I could only find C&D that does that.
> > >
> > > - sounds like two converters and your done.
> > 
> > Except that two converters are more than twice the price and consume twice
> > the space.
> 
> You can't get something for nothing.  If you want two isolated
> converters, there will not be much circuitry to share.  So two separate
> units will not be much larger than one combined unit.  More importantly,
> if you can't find a combined unit that meets your needs, you may have to
> use two separate units.  

Alternatively, he could do his own if he can manage to wind his own
transformer. I often need several isolated DC supplies so I just wind
up a transformer with the requisite number of secondaries and configure
a simple chopper to drive it. 

-- 
********************************************************************
Paul E. Bennett ....................<email://peb@amleth.demon.co.uk>
Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972 .........NOW AVAILABLE:- HIDECS COURSE......
Tel: +44 (0)1235-811095 .... see http://www.feabhas.com for details.
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

Meindert Sprang wrote:
> 
> "Bobsprit" <Bobsprit@aol.com> wrote in message
> news:bxi6c.11301$E8.2842421@news4.srv.hcvlny.cv.net...
> > ,the dual output is not what I want. Most dual-output types ar +/-
> > > outputs. I need two independent 5V outputs, isolated from eachother too.
> > So
> > > far, I could only find C&D that does that.
> >
> > - sounds like two converters and your done.
> 
> Except that two converters are more than twice the price and consume twice
> the space.

You can't get something for nothing.  If you want two isolated
converters, there will not be much circuitry to share.  So two separate
units will not be much larger than one combined unit.  More importantly,
if you can't find a combined unit that meets your needs, you may have to
use two separate units.  

-- 

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design      URL http://www.arius.com
4 King Ave                               301-682-7772 Voice
Frederick, MD 21701-3110                 301-682-7666 FAX

"Bobsprit" <Bobsprit@aol.com> wrote in message
news:bxi6c.11301$E8.2842421@news4.srv.hcvlny.cv.net...
> ,the dual output is not what I want. Most dual-output types ar +/-
> > outputs. I need two independent 5V outputs, isolated from eachother too.
> So
> > far, I could only find C&D that does that.
>
> - sounds like two converters and your done.

Except that two converters are more than twice the price and consume twice
the space.

Meindert

On Thu, 18 Mar 2004 14:40:07 GMT, the renowned "Bobsprit"
<Bobsprit@aol.com> wrote:

>,the dual output is not what I want. Most dual-output types ar +/-
>> outputs. I need two independent 5V outputs, isolated from eachother too.
>So
>> far, I could only find C&D that does that.
>
>- sounds like two converters and your done.

Maybe build a non-isolated buck converter to regulate the input (stock
magnetics) and put a couple of the B-B jobs on the output. 

Best regards, 
Spehro Pefhany
-- 
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

,the dual output is not what I want. Most dual-output types ar +/-
> outputs. I need two independent 5V outputs, isolated from eachother too.
So
> far, I could only find C&D that does that.

- sounds like two converters and your done.

"Greg Neff" <greg@microsym.com> wrote in message
news:8k3h501cnrd2ntvacvkjl97uuogpj2dr32@4ax.com...
> On Wed, 17 Mar 2004 07:48:53 +0100, "Meindert Sprang"
> <mhsprang@NOcustomSPAMware.nl> wrote:
>
> Not true.  There are excellent BB 1W (DCP01) and 2W (DCP02) isolated
> converters available in standard DIP and SO packages, and we use them
> extensively.  Unfortunately, they don't have the wide input range that
> you are looking for in this application.

Also, the dual output is not what I want. Most dual-output types ar +/-
outputs. I need two independent 5V outputs, isolated from eachother too. So
far, I could only find C&D that does that.

Meindert