Hello everyone,

Searching all over the internet i always find different design for traic controlling a lamp. so i chose one to implement and it worked fine or it looks so.
http://www.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit/?ALLSTEPS

But I used:
MOC3022 with BTA06 instead

I had problems with understanding the gate resistor value which is 1K in the above circuit. Before asking on the forum I tried searching and I understood that this resistor is used to protect the optocoupler, so using MOC3022 with current max to 1 A with 220 V, so a value of 240*1.4V/1A = 336 ohm or 360 ohm is enough. But here comes another question.

What about the Triac ? I use BTA06 which is listed to have IT RMS = 6 A, and IGT = 5-50 mA & IGM peak current gate = 4A pulsed for 20 us. which value do i care for ?

Assume that a resistive/inductive load needs 3A to operate. Will the MOC3022 work with this load ? or Does this load drops only on the TRIAC itself between MT1 and MT2 and not related to the opto coupler ?

Also After searching again I found also this application note which states how to calculate gate resistor - attached. but didn't illustrate the above paragraph.

So..

1- Is there any relation between the load current and the gate resistor value for opto-coupler max current ?

2- What is the difference between IG & IGT ? which one do i need ?

3- Can I use MOC3022 with BTA06 to drive a resistive/inductive load equals to 3 A ?

I hope that i am clear enough.

Thank you in advance.

 

1- Is there any relation between the load current and the gate resistor value for opto-coupler max current ?

No

2- What is the difference between IG & IGT ? which one do i need ?

IG is minimum gate current IGT is maximum. However: the 5 to 50 number is for the logic level part, the standard may be 0.1 amps. I would stick with the 1K so the MOC3022 is cool.

3- Can I use MOC3022 with BTA06 to drive a resistive/inductive load equals to 3 A ?

Yes

QUOTE]

 

So if there is no relation between them:
1- The high load will pass only through the wires connected between the two pins of the Triac ?
This is regarding pcb design, These wires between the two wires must withstand the load current, while the wire/trace between the Triac and optocoupler will have low current through them. Am I right ?

2- So, Don't i specify current through the gate ?
And, for the 1K resistor, the minimum value is 360 ohm which will withstand the 1A but increasing it won't affect as long as the current passing will operate the optocoupler. Am I right ?

Thank you very much.

 

okay regarding number 2,
I wrote IG = 5-50 not IGT, and IGT = 4A not IGM
You said the min current is 5-50 mA and max equals to 4A, so the current passing is the one also passed through the moc ? so this resistor is chosen to passing the current which suits both chips ?

 

Yes, it needs to be high enough to turn on the triac but not so high as to burn out the MOC.