On Fri, 14 May 2004 18:48:37 +0100, "Paul E. Bennett"
<peb@amleth.demon.co.uk> wrote in comp.arch.embedded:

> Rodo wrote:
> 
> > Hi all,
> > 
> > I need 5 independent power supplies. I can use a single transformer with 5
> > secondary windings but I haven't been able to find one (Vin=115vac ok). Is
> > there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).
> > 
> > Thanks
> 
> At the power rating you have the transformer cores in RS would be OK
> for winding your own. I have made several transformers of this
> configuration myself (although using a lower input voltage) in a
> switcher for a DC-DC converter.
> 
> Unlike the un-imaginative respondent I can guess why you need 5
> isolated supplies.

...and I can guess that your guess is wrong! :)

-- 
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.learn.c-c++
http://www.contrib.andrew.cmu.edu/~ajo/docs/FAQ-acllc.html

On Fri, 14 May 2004 01:58:36 GMT, the renowned "Rodo"
<dsp1024@yahoo.com> wrote:

>Hi all,
>
>I need 5 independent power supplies. I can use a single transformer with 5
>secondary windings but I haven't been able to find one (Vin=115vac ok). Is
>there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).
>
>Thanks

You could always use 3 transformers with two secondaries each. 

Do note that the secondary-to-secondary isolation (both voltage and
capacitive coupling) is usually inferior to the primary-to-secondary
isolation (depending on the construction of the transformer). Often
the maximum voltage rating is not stated. 


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

On Fri, 14 May 2004 01:58:36 GMT, "Rodo" <dsp1024@yahoo.com> wrote:

>Hi all,
>
>I need 5 independent power supplies. I can use a single transformer with 5
>secondary windings but I haven't been able to find one (Vin=115vac ok). Is
>there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).
>
>Thanks
>

C&D Technologies makes small isolated DC-DC converters that could be
used for this.



-- 
Peter Bennett VE7CEI 
email: peterbb4 (at) interchange.ubc.ca        
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html 
Newsgroup new user info: http://vancouver-webpages.com/nnq

Rodo wrote:

> Hi all,
> 
> I need 5 independent power supplies. I can use a single transformer with 5
> secondary windings but I haven't been able to find one (Vin=115vac ok). Is
> there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).
> 
> Thanks

At the power rating you have the transformer cores in RS would be OK
for winding your own. I have made several transformers of this
configuration myself (although using a lower input voltage) in a
switcher for a DC-DC converter.

Unlike the un-imaginative respondent I can guess why you need 5
isolated supplies.

-- 
********************************************************************
Paul E. Bennett ....................<email://peb@a...>
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..
********************************************************************

On Fri, 14 May 2004 01:58:36 GMT, Rodo wrote:
> Hi all,
> 
> I need 5 independent power supplies. I can use a single transformer with 5
> secondary windings but I haven't been able to find one (Vin=115vac ok). Is
> there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).

A transformer, rectifier and capacitor and 5 500mW or 1W DC-DC converters?

-- 
Trevor Barton

"Rodo" <dsp1024@yahoo.com> wrote in message
news:gJVoc.193988$L31.60101@nwrddc01.gnilink.net...
> Hi all,
>
> I need 5 independent power supplies. I can use a single transformer with 5
> secondary windings but I haven't been able to find one (Vin=115vac ok). Is
> there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).

Get a transformer made.

Leon

In article <gJVoc.193988$L31.60101@nwrddc01.gnilink.net>,
Rodo <dsp1024@yahoo.com> wrote:
>Hi all,
>
>I need 5 independent power supplies. I can use a single transformer with 5
>secondary windings but I haven't been able to find one (Vin=115vac ok). Is
>there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).

Maybe we need to back it up a bit. Why do you need 5 independant power 
supplies? Do the circuits need to be electrically isolated from each other?

5 secondaries is a stretch. So why is the isolation necessary?

BAJ

Hi all,

I need 5 independent power supplies. I can use a single transformer with 5
secondary windings but I haven't been able to find one (Vin=115vac ok). Is
there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each).

Thanks