- What are the wattages of resistors at the HOT side?
They can be 1/4 W 5%. Only the Triac sees the load current.
- What is the difference between 360Ω and just 330?
The 360 ohm limits current into the opto-isolator and triac gate. The 330 ohm acts as a pull-down resistor to make sure the triac if OFF when there is not drive current from the opto-coupler. It keep the triac trigger input from "floating". NOTE: The triac MUST trigger ON as expected or the resistors and the opto-coupler may burn up. The resistors should be the flame-proof type.
Note that the 'R' values are chosen to match the triac gate drive needs without burning up the opto-coupler. Over a wide range of triacs both resistors can vary a great deal as long as the triac ALWAYS turns ON when expected and OFF when the opto-coupler is OFF. There are sensitive gate triacs used in motion-detect nightlights that have a 100 K resistor in series with the gate driven by an op-amp or mini MPU with just 5 to 10 volts.
- The capacitor 0.01, is it micro farad or something else?
When you see a decimal point in a capacitor value, it is normally in uF. If in Farads or pico farads it should state so. Nano farads are often written as xxnF. It should have an X2 rating, or twice the AC line voltage.
- Is this circuit safe for inductive as well as resistive loads?
It is as long as the triac is rated for the start-up current of a motor, or 3 times the amp rating of an electromagnet. Note that for heavy inductive loads a 40mm MOV across the triac will act as a snubber. It should be rated 50% above the AC line voltage.
- Is this a practical circuit which will not cause any false trigger?
This is as simple as it gets. If there is a false trigger it is coming from the logic driving it. If driven by software it much be clean and checked for any chance of errors.
- Can any triac be used?
That is a loaded question because the triac needs to be rated for the voltage of the AC line plus 50% for a safety margin. It needs to be rated for 3 times the maximum continuous load current. This affects the package it is in as well. To drive a tiny night light a tiny 3 pin triac will work. To drive a 10 horse power motor it will be large and need to be bolted to a large metal heatsink of aluminum.