I'm trying to build a dual power supply. I can find mains transformers that give me two (presumably unconnected) secondary windings of equal voltage, and if I connect them in series, I should be able to make myself a transformer that should behave like a center-tapped transformer.
Obviously, if one of the secondary windings has terminals A and B and the other has C and D, I could connect either A to C (equivalently B to D) or A to D (equivalently B to C). If the first winding has the dot at A and the second has the dot at C, my intuition tells me that I need to connect A to D (or B to C), and that the other connection (A to C or B to D) would be wrong, correct?
If you want a specific example, take a look at this datasheet: https://www.mouser.ch/datasheet/2/410/FP34_1400-781326.pdf
This transformer has two secondary windings of 17VAC each, and one winding on pins 5 and 6 has the dot at 5, and the other on pins 7 and 8 has the dot at 7. So I think I could connect 5 to 8 or 6 to 7, but not 5 to 7 or 6 to 8. Is that correct?