Source a transformer with multiple secondaries

[MarkF]

I would like to build a simple linear power supply with three outputs (i.e. 5VDC, +12VDC and -12VDC).
I want to keep the 5V GND independent of the +/-12V GND.  Only looking for a 1A capability max on each output.

Does anyone know where I can find a single transformer with three secondaries instead of two transformers?

   

   

[schmitt trigger]

Perhaps the easiest would be to purchase a toroid transformer which can provide the +/- 12v supplies, and then hand wind your own winding for the 5v supply. Window area allowing it, of course.

[station240]

You can get multitap transformers, been out for decades.
I have no idea where you get them in the US, all the electronics stores in Australia sell them.

Try searching ebay for "transformer 9V+9V 15V+15V", seems to be some usable results there.

[Benta]

Or just get it made to order. No big deal nowadays. There are transformer companies that'll make one-offs. Search the interwebs.

[Zero999]

Digikey sell them but the power rating for the 12V secondary is a bit less than your requirements, at only 250mA.
https://www.digikey.co.uk/product-detail/en/signal-transformer/14A-30-512/595-1705-ND/1117954

How about using two transformers or a switched mode power supply for the 5V part, which presumably isn't so sensitive to noise and ripple?

Another option is to use a transformer with two secondary windings with one connected to a voltage doubler to get the +/-12V, although it would need to be considerably over-rated.