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Power supply transformer connections

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MarkF:
This is an old transformer I was going to use.
My project needs +/-12V and 5V.  The 500mA is probably twice the actual load.  If that.

Maybe I can just use two full wave bridges on a PCB I did.

   

   

MarkF:
Here is the original circuit I was trying to adapt.
I thought it was using a full wave bridge.
After closer inspection, it is not.

   

Ian.M:
Your transformer's 7.7V-0-7.7V winding + a bridge rectifier and two resevoir caps between bridge + and winding CT, and CT and - can feed your +5V (from CT) and +12V regulators reasonably efficiently,  and use the 14.4V winding + another bridge and reservoir cap to feed the -12V regulator.

MarkF:
Will the 5V regulator input be halfwave rectified then?

   

Ian.M:
Nope.  Full wave.  Consider the CT as ground and you'll see that both the bridge + and - have equal and opposite full wave rectified voltages.  Now consider output 0V (bridge -) as ground and you'll see that the +12V regulator gets the full wave rectified  whole winding voltage and the CT provides the 5V regulator with half of that so neither should run excessively hot. 

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