One thing to remember is that some of the coils will be
carrying current from more than one output. If the common is
on the end, that coil will carry all of the current from all
of the outputs.

Allen

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-
> bounces@mit.edu] On Behalf Of IVP
> Sent: Friday, February 3, 2017 6:18 PM
> To: Microcontroller discussion list - Public.
> Subject: [EE] Multi-tap transformers, multiple bridges
>=20
> Hi all,
>=20
> I've got a couple of circuits which need 3 DC rails, 5V,
7V and
> 13V. The 13V is ~ 50mA, the 7V ~ 100mA and the 5V ~ 200mA
>=20
> Is there any reason a multi-tap transformer can't be used
with
> a
> bridge on each relevant tap, followed by regulation for
each
> rail
> with an LM317 or 780x. I've got 15V 20VA transformers with
> taps at 3V intervals
>=20
> Googling around hasn't brought up any images of somebody
> doing it. More likely is to use a transformer with one
> secondary
> and regulate down to all voltages from that or a
transformer
> with
> a secondary for each voltage
>=20
> So I could use the 12V tap -> 17VDC and derive the 3 rails
> from
> that, I just wonder if in principle there's any reason why
it
> can't be
> done with separate bridges. I've another project in mind
> which
> would need 6V @ 1.5A and 15V @ 50mA. It seems a waste to
> rectify for a 15VDC rail and then chop most of it back to
6V
>=20
> TIA
>=20
> Joe

--=20
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