Can you "unbalance" the load on a transformer with multiple secondaries?

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Joined May 17, 2012
I've got a transformer that puts out two secondaries at 10v which can be bridged to make 20v as if it were a single 20v secondary with a center tap. Can I feed a 12v regulator off the combined secondaries while also feed a 5v regulator off of only one of the two secondaries to keep down the heat waste at the 5v section, or will that cause some kind of imbalance in the transformer? My end goal is to have a single power source for my raspberry pi, powered usb hub (both need just the 5v) and an external hard drive, which needs the 12v. Right now I'm running the pi off of the hub but I've still got 2 wall warts and I'd like to streamline things as much as possible. The spec sheet for the transformer is There are many models covered in that one pdf. The specific one I have is 164H20.


Joined Nov 30, 2010
Sure. The limit is how much power you use from each winding. They don't have to be any where near equal.

You have a transformer rated at 1 amp so you can only get .28 amps of DC out of this configuration. I don't think that's going to provide enough power. The hard drive in my right hand says it needs .47 amps of 12 volt power.


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