How to select resistances for bt136-600e?

Question

Arduino

Good day, dear ones!
I am assembling a relay on an optocoupler with a moc3063 triac output and a bt136-600e semistor.
In the original circuit, instead of bt136, bt138 is used, but there is no such sevenistor at hand.

Please help me understand how to calculate the resistance from the optocoupler going to the sevenstor.
With the resistances indicated in the bt136 circuit, it does not open.

Answer 1

Here you need to understand that the values ​​​​of these resistors are selected ... a little "from the bulldozer". Although, some calculation base can be brought under this choice. Let's say R3 is too big, in my opinion, it needs to be reduced by 2...3 orders of magnitude. Its value is determined by draining the leakage current of a closed optocoupler triac so that the main triac is also clearly closed, and this is the more reliable the lower this value (at 500 kilohms, the main one can open even from pickups). And when opening, this value is indifferent, since the control current, set by the value of the resistor R2, is certainly enough to open the main triac with a large margin.
Now about R2. No matter how much you take in the range from 100 ohms to several kilo ohms, the received current will still be enough to open the triac (of course, when the load circuit is powered from 220 volts). But if there is less voltage, then the choice of R2 becomes more critical. But in any case, knowing the maximum required control current, which opens the main triac, it will not be a problem to calculate R2. Just remember that with a very low resistance R2, the optocoupler triac will, which is good, work instead of the main one, and this should not be allowed.
And finally, about BT136. In addition to reducing the value of R2, I recommend also reducing R1, to 200 ... 300 Ohms. There is some dependence of the clarity of the operation of the optocoupler on the current through its LED - so increase this current. Well, try to replace it, it can be dead.