I am looking for trhe most economical way to convert 12VAC to 24VAC. I am trying to interface 2 products together, One works on 12VAC (inside it is converted to DC), the other requires 24VAC input(A home thermostat). Ideally I would like to operate them both from the existing 12VAC source.

The current on the 24VAC side will be no more than 100ma, this thing has to be small. Iw as considering a voltage doubler circuit and wanted to try that, however I didn't have much luck with the values of the capacitors in any of the schematics that I found.

One thought I had was to possibly use a 2:1 ratio transformer. Would this be possible?

Any other Ideas or suggestions would be greatly appreciated.

 

A 1:2 ratio transformer would be your most simple option.
If you require 100mA @24vac, you'll need somewhat more than 200mA @12vac on the primary side, because transformers aren't 100% efficient.

 

The Transformer that is existing is a 20VA unit, and is somewhat oversized for it's aplication however, that means that I would have plenty of reserve power for the conversion.

Now the next question:

It seems that the transformers that I have been able to find are aparently signal transformers (especially the ones that are a 2:1 ratio). Does anyone know of a source for these types of transformers?

thanks,
Michael

 

Actually, why don't you just replace the 12vac transformer that you're using to power the 1st item with a transformer that has a 24v center tapped secondary?
You'll get 12vac from one end to the center tap, and 24vac between the ends.

Here's one for under $6:
http://www.mpja.com/prodinfo.asp?number=7844+TR
I've used this supplier a number of times. Never had a problem with them.

You could also use this $11 transformer from Digikey:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=595-1056-ND