TRIAC Gate...

I bought 3 triacs (never used one before) thought about hooking them up to a low voltage AC to test how they work..

thing is, I've read the gate requires a positive or negative? so on 0v/gnd it does nothing? is that true?

Yes, triacs need a certain gate current to trigger. They remain on till the current in the main terminals falls to a low level (at the zero crossing).

You need a resistor to limit the gate current don't forget. A triac is just two SCRs wired back to back, so a positive gate voltage will turn on with only positive going supply waves and a negative gate voltage will turn on with only negative going supply waves.

http://incredulist.blogspot.com/2012/11/ac-phase-control-triacs.html

I used the circuit diagram on the bottom of page 7 to hook up a set of triacs for a dishwasher controller:

http://www.fairchildsemi.com/ds/MO/MOC3041M.pdf

Works well and has the safety of opto-isolation.

Grumpy_Mike: A triac is just two SCRs wired back to back, so a positive gate voltage will turn on with only positive going supply waves and a negative gate voltage will turn on with only negative going supply waves.

Not entirely accurate. MT1 and MT2 are not interchangeable with regards to the gate, which it could if a Triac truly were two SCRs wired back to back. The gate must be driven with reference to MT1, or the Triac will not function correctly.

This link has more info: http://www.allaboutcircuits.com/vol_3/chpt_7/6.html

As far as which quadrants can be used, it depends on the Triac. Best to read the datasheet. Some work best as you describe, some work better with only negative gate drive. Some, such as this one, work well with any polarity gate drive (top of page 2): http://www.nteinc.com/specs/5600to5699/pdf/nte5608_10.pdf