device differences?

Sorry to ask what may appear a daft question, but whats the difference, if any between a Variac and a DC Bench Power Supply please?

A variac is simply a variable auto-transformer - just a 'brush' which rubs across the windings and thus alters the voltage out. It's AC in, AC out, almost always not isolated, and not regulated.

A DC power supply is AC in, DC out, usually regulated, and even more usually isolated.

Totally different items, for totally different purposes - if you had to ask, DON'T buy a variac, they are pretty dangerous items.

Discussion on variac safety -




Regards, Dana.

A variac varies the mains voltage, but it’s still mains. One side of the output is connected to one of the mains wires, and you should always regard line and neutral as potentially live, so you should always regard both output lines of a variac as potentially live.

If you wanted a variable ac voltage around 3V, you could connect the input of a 9V or 6V transformer to the output of a variac. The low voltage transformer would provide safety isolation so you could mess around with the low voltage output safely, and you would be setting the variac near mid-range, so you would get much finer adjustment of the 3V.

However a cheap variable dc supply is cheaper, smaller and most likely far more suitable.

Thanks for that info. I will take your advice. I have a varian, and an Iso, as well as a bench supply, but until I am absolutely certain of what I am doing, I will not meddle!