A/C switching through PC

[owais86]

Hi all
   
  Am working on a project for switching air conditioner A/C on and off through PC. The main idea is to use PC parallel port to switch  the A/C. I have designed a circuit (schematic attached). As i have no experience of playing with [glow=red,2,300]mains[/glow]. So i need some comments/advise on this circuit will it work and how to make it safe.

Thanks all

[owais86]

;)Its working fine on ISIS  8)

[Hero999]

That will work, assuming the opto-isolator is rated to carry the relay current.

It seems a bit overkill to use both an opto-isolator and a relay.

I would have used either an opto-TRIAC triggering a TRIAC or a transistor and relay.

Relays are more fail safe than TRIACs but have the disadvantage of requiring a power supply. An opto TRIAC triggering a TRIAC can take all the power it requires from the parallel port.

[owais86]

That will work, assuming the opto-isolator is rated to carry the relay current.

It seems a bit overkill to use both an opto-isolator and a relay.

I would have used either an opto-TRIAC triggering a TRIAC or a transistor and relay.

Relays are more fail safe than TRIACs but have the disadvantage of requiring a power supply. An opto TRIAC triggering a TRIAC can take all the power it requires from the parallel port.

So you mean that i should use opto triac like MOC 30XX....... and another TRIAC with it? Y 2 TRIACz?

[Hero999]

A typical opto-TRIAC can only take a couple of hundred mA which isn't enough for an air conditioner.

It's up to you, you could use a transistor and relay if you like.

All I'm saying is that it's wasteful to use both an opto-isolator and a relay.