Why do I need a Variac?

[ctwo]

I bought one of the cheap red ones from ebay. I powered it up, watched the voltage reading as I twisted the knob, verified it with my DMM, and then put it back in the box and on the shelf.

I have a few bridge rectifier blocks that I suppose I could use to create a variable DC power supply, with the right caps and minding the lack of isolation. I could also power a couple of very large speedless fans (one 48").

[tornitore45]

Watch out for the lack of isolation when attaching a bridge rectifier to a variac.
You have the positive going positive for half cycle and then -1V for the next semicycle
An then the negative going negative for half cycle and then -1V for the next semicycle

It remind me of one night in Italy I had a dead car battery, it was raining heavy and the service station was two miles away.

Connected a bridge to the 220V AC with an Ironing Iron as a ballast. Did a couple of calculation and concluded the battery would be charged early in the morning. The entire car was floating at 220V.

[John Hasler]

Watch out for the lack of isolation when attaching a bridge rectifier to a variac.
You have the positive going positive for half cycle and then -1V for the next semicycle
An then the negative going negative for half cycle and then -1V for the next semicycle

It remind me of one night in Italy I had a dead car battery, it was raining heavy and the service station was two miles away.

Connected a bridge to the 220V AC with an Ironing Iron as a ballast. Did a couple of calculation and concluded the battery would be charged early in the morning. The entire car was floating at 220V.

A friend of mine had folding battery charger he carried in a sack. A zip cord with a two wire plug, a capacitor off a motor for current limiting, four rectifiers, and cables and clamps. All soldered up with lengths of stranded wire. No frame, case, or breadboard: just an amorphous network. To use it he would spread the mess out on a blanket, newspaper, or just dry ground, make sure nothing was touching anything it shouldn't touch, clamp the clamps to the battery terminals, and plug it in. He suggested that it might be best not to touch the car.

[tornitore45]

That is exactly what I did but uses a dissipative ballast instead of a reactive one. The typical Italian household has much less DIY equipment than he American one. I was not yet at the point in my life when I had accumulated a garageful of junk, the ironing iron was the only power "resistor" available and perhaps light bulbs but they would have been harder to wire up.

[John Hasler]

But did you store it in a sack behind the seat of your old pickup truck and use it routinely? I believe it finally died when the capacitor overheated and popped.

I think that George may have reached the point in his life when he had accumulated a garage full of junk at about age six.

[tornitore45]

I am not as minimalistic as some guys. But it just goes to say that great minds think alike. LOL

[ctwo]

I have verified that the transformer's fuse properly protects 14ga house wire and that enameled wire smells when it gets hot.