Triacs are designed to work with pulsing trigger, that means you shouldn't connect it directly to the 555 and that's why all triacs triggering uses a opto or transformer interface.
The triac trigger should be done by spikes of curret and because you are switching AC (60Hz), it have to be triggered many times every cycle.
The circuit attached was designed to generate the triggering pulses.
By the way, the symbol you are using for triac in fact is a XOR gate.
If I was you I would use three small relays. Would work the same way and you could save couple $. Pulse transformer cost a bit.
Nilo
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Nilo
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26th December 2003, 10:19 PM
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