Difference between 2 circuits in white paper.

Other Hardware General Electronics
1

I am looking at the PDF for an optocoupler MOC3010M.

https://www.fairchildsemi.com/datasheets/MO/MOC3010M.pdf

I'm trying to figure what is the difference in purpose, function, or application between figure 11 on page 6 and figure 12 on page 7.

The value of 1 Resistor and Capacitor, which I believe are a snubber, is the only difference that I see.
Which one of these should I use to turn on or off a over the counter electric space heater with fan. 120VAC 1500 w.

Thank You.

2

jarrod0987:
I'm trying to figure what is the difference in purpose, function, or application between figure 11 on page 6 and figure 12 on page 7.

None that I can see. Essentially, both have the same time constant.

jarrod0987:
Which one of these should I use to turn on or off a over the counter electric space heater with fan. 120VAC 1500 w.

Toss a coin.

More to the point, see what capacitor is on hand (rated 150VAC) and then choose your resistor.

3

Don't "snub" their extensive app note which may have some answers. :wink:

Note that the 1500W space heater/fan would have a much higher resistive load component than inductive. I would think this R-L load would act as its own snubber.

4

Looked through the ap notes that were posted. Uhhh. Little too much info overload. I get that Triac is basically a switch for AC. Sometimes if you have too much noise on the line caused by a motor or some such thing you may get false triggering. Hence a snubber which is basically a filter. IS that about right?

Looking at the simple resistive load circuit example in the white papers I am surprised to see the only thing in between the full 120vac and the detector side of the optocoupler is only a 180 ohm resistor. Doesn't this mean the full 120VAC will be applied to the gate at times? This doesn't damage the triac?

Thank You

5

Sometimes if you have too much noise on the line caused by a motor or some such thing you may get false triggering. Hence a snubber which is basically a filter. IS that about right?

Yes.

Looking at the simple resistive load circuit example in the white papers I am surprised to see the only thing in between the full 120vac and the detector side of the optocoupler is only a 180 ohm resistor. Doesn't this mean the full 120VAC will be applied to the gate at times? This doesn't damage the triac?

No - most of the 120VAC will be dropped across the resistor.