Triac for home automation ?

Hello expert

was using relay board to controlled 240vac but was thinking to use triac and opto as they are small in size. but had some doubt that will i be able to keep triac in default on state so that after the powercut the load will become On. as in case of relay com and nc are shorted default so my load weill become on after powercut. is it same possible in triac ?

Thanks in advance

If you are using an Arduino to control the thing you can turn the TRIAC on every time the program re-starts at power-on.

You could also do the same thing in hardware, making the default state turn-on the TRIAC. i.e., You can use an inverter or you can wire-up the LED-side of the opto-isolator so that current flows when it's pulled-down.

However, unlike a relay, you can't turn-on the TRIAC without a control voltage on the opto-isolator input. If the control side power comes from the 240V, that's not an issue because there's no point in turning-on the 240V when the power is off. But, if the control side power comes from a battery (etc.) the 240V side couldn't default to on with a dead battery.

DVDdoug:
If you are using an Arduino to control the thing you can turn the TRIAC on every time the program re-starts at power-on.

You could also do the same thing in hardware, making the default state turn-on the TRIAC. i.e., You can use an inverter or you can wire-up the LED-side of the opto-isolator so that current flows when it's pulled-down.

However, unlike a relay, you can't turn-on the TRIAC without a control voltage on the opto-isolator input. If the control side power comes from the 240V, that's not an issue because there's no point in turning-on the 240V when the power is off. But, if the control side power comes from a battery (etc.) the 240V side couldn't default to on with a dead battery.

Hey DvDdoug thanks for the reply

I didn't got you by inverter and those wiring things with led opto can u pls explained me in deep as I was totally new to electronics

Thanks in advance

as I was totally new to electronics

In which case you must NOT play with mains electricity, you will start a fire or kill yourself.

Grumpy_Mike:
In which case you must NOT play with mains electricity, you will start a fire or kill yourself.

Dont worry i will take necessary precaution with 240v ac as i already did this with relay

Look in to SSR's solid state relays. They have most of the benefits of using a triac and opti. but are easy and safe to use. for the beginner i suggest the kind of ssr that has screws for connection but if size is a problem small pcb mount SSR's are available and some can handle pretty high current.

I have done a home automation project with btb15 triacs and K3023P optis but i ran into a lot of problems mainly in physical build and design of the pcb board and heat when the triacs were loaded hard.
Having 64 120v outputs on a pcb and trying to keep it as small as possible was a bad idea. i am currently redoing the project using rf24 radios and arduino pro minis with 2 ssrs as a self contained wall switch insert.

If you do use a triac make sure to use an opto-isolator like the Motorola MOC3010 series. I made a project back in the seventies that used these and a TTL counter to dim lights programmatically. Wasn't hooked up to the internet though. 8^)

AC PHASE CONTROL