12V AC Power Supply

In a lot of electronics I bought there was a small variac. Unfortunately I could not find a datasheet, but after some experimentation I found out it was for 12V AC. Laying on the shelve it was quite useless, so I decided to make an low voltage AC power supply with it.

To determine the max input voltage, I measured the zero load current and put it with the input voltage in a graph:

From this graph I concluded that as long I stay below 15V saturation is not a problem. Therefore I have chosen to use it on 12V.

I build it in enclosure together with an 12V halogen transformer. Also I readout based on that of my Safety transformer V2 & Safety transformer V3, the version in this project however is adapted to measure lower voltages, so the resolution increases. Also a power supply for the meters is added.

Complete unit:

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