# Double secondary winding equal to center tap?

I am trying to create a power supply with both positive and negative voltages. Is it possible to use this transformer to create such a supply? : https://my.element14.com/vigortronix/vtx-146-050-215/50va-toroidal-transformer-2x15v/dp/2817652

Basically, want to use the center tap of a transfomer's secondary winding to create both negative and positive voltages with common ground. But I am not sure if the mentioned transformer's double secondary winding can be used to do such a thing. Is it two separate secondary windings without any connections in between? What if I connect two wires from each secondary winding together and use that as the GND ground? Will that method work? Or the voltages will be out of phase? Please need some help regarding this. Thank You.

• In center-tapped transformers, the two windings are just connected together by default at the terminal block. Commented Jun 17, 2021 at 22:48
• "want to use the center tap of a transfomer's secondary winding to create both negative and positive voltages with common ground" -- you are aware that a transformer works with AC, so there's no negative and positive voltages there, per se.. Yes? Commented Jun 17, 2021 at 23:33
• presumably he wants ti use it with a bridge rectifier to produce a +/- DC supply with a ground. this is a comon design. eg the schematic in this question: electronics.stackexchange.com/questions/478019/… Commented Jun 18, 2021 at 2:33
• yes that is a the goal. using a bridge rectifier and common ground. Commented Jun 18, 2021 at 12:45

## 2 Answers

If you connect them together correctly you'll have the equivalent of a center-tapped winding.

You can think of the "dots" on the windings as the equivalent of (say) + polarity on a DC source such as a battery- you want to connect + to - to get them to add.

Note that it's equivalent to a center-tapped winding of $$\2\cdot V_{Sec}\$$, not $$\V_{Sec}\$$.

Yes, the two secondaries can be connected together (e.g. black and yellow) to have a center-tapped output.