Yes, triacs do conduct in both directions and can be triggered with either polarity as well. In other words, all combinations of positive and negative voltage on the main terminals and trigger terminal are able to trigger conduction using a single triac. The sensitivity can however vary depending on the particular combination.
John
Yes, The silicon controlled rectifier is the unidirectional one: Triacs are almost a pair in parrallel.
Lots of interesting and educational stuff.
I?d not have thought of building a timer out of capacitance decay.
I had a look at the YouTube video, and read the comments and someone there had also traced the circuit and (I think) explained it.
Having heard how hot that resistor can get, I?m glad mine is mounted in a relatively large enclosure.
Perhaps I should add some ventilation!
They are more complicated than a "diode".
FYI
A Thyristor conducts in one direction
That's why triacs are sometimes fed by diacs.
The one I built-up at home forty years ago, used a diac.
Paul
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