Loads: Some baseboard heaters (1500W max, some motors, 12A max).

I have no experience using Triacs and optocouplers.

Triac: T3035H-6T, Datasheet: http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00263568.pdf

Optocoupler: MOC3062SM, Datasheet: http://www.mouser.com/ds/2/149/MOC3062M-196063.pdf

Optocoupler is driven by a 5V micro controller output which will be on as long as the load needs to be on.

I am planning to control the Triac with the MOC3062SM optocoupler, and would like your comments on the example circuit in the datasheet (Basic Applications).

I am uncertain about how to dimension (watt) the two 360 ohm resistors on the 240VAC load example.

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I mean, if the optocoupler triac is conducting as long as LED is on, then 1/3A is flowing in the resistors, and producing a cozy 80W. So I guess I am not understanding the workings of the optocoupler, as I cannot believe we need to dissipate that kind of heat.

EDIT: I just realized the 1/3A is just momentary, the load takes the bulk of the voltage as soon as the triac fires...

Or does the optocoupler switch off a certain number of degrees into the cycle?

Your input will be appreciated.


1 Answer 1


This is an ON/OFF controller. When opto-coupler is ON, the load is "ON"

Or does the optocoupler switch off a certain number of degrees into the cycle?

The load is not switched off/on as a matter of degrees. The load is "on" according to your command to the opto-coupler. As long as your input to opto-coupler is sustained, the load is engaged, (on).

Your "edit" re : "1/3 A is momentary" is correct"


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