Earth ground on power supply question.

HI,

I'm making a variable voltage DC power supply using a standard LM317 circuit.

Should I connect the negative side to the ground on the AC power connector? I'm talking about the actual "earth" ground on the IEC connector, where the the line and neutral connect to the power transformer.

Thanks

- Rick

If your output doesn't need to float relative to earth (some supplies can & some applications desire this), then yes connect to earth for safety reasons.

Some times it's useful, sometimes it's not, and some times it could be dangerous?.

You could make it switchable, or have three output terminals, positive, negative, and ground - and connect them as required - you could even have a metal strap that links between ground and either of the other terminals (some times you might want the positive grounded).

Basically it's a personal decision, depending on how you might want to use it - but a permanently grounded negative will reduce it's usefulness.

Okay, thanks. I was already going to ground the metal case to earth, I think I will add a switch for ground/float on the power supply circuit and possibly a ground terminal on the front panel.

- Rick