Logic Level Triac Controlled By Moc3031

[xavier]

Can a logic level sensitive triac (such as MAC97A8) be controlled with a MOC3031 or similar triac driver? Or does it need to be lower voltage at the gate from an microcontroller?

[Sch3mat1c]

Sure, you can get away with a much larger series current limiting resistor, perhaps 1kohm would be fine.

Tim

[xavier]

As always thank you for the reply!

[xavier]

I set this up and the MAC97A8 triac won't turn on. Is there a minimum load that must be there for the MAC97A8 to turn on? I'm trying to control a relay that has a 110vac coil. The coils rated current is 20ma and the coil resistance is 2360 ohms, coil power is 2VA

[MacFromOK]

Not sure how familar you are with triacs, but here are a few of the basics.

- The main pins are called main terminal 1 (MT1) and main terminal 2 (MT2). There's also a gate drive pin.

- The gate drive must be referenced to MT1 (i.e. driven from the MT2 side), and the load should always be placed on MT2 (not MT1). Placing a load on MT1 causes AC voltage to appear across the gate resistor and it will overheat.

- The data sheet should specify gate trigger current (Igt). The gate requires a series resistor (value should be drive voltage divided by Igt + 20% to give it some margin). If resistance is too high, the TRIAC will not turn on or only turn on half the cycle.

- The gate will trigger with a signal of either polarity. A negative gate signal (instead of positive with respect to MT1) requires less current. However, not all triacs respond well to a DC gate signal.

- Gate current for a "sensitive gate" triac is usually under 20mA.

- Once triggered, the device continues to conduct until the current through it drops below a certain threshold value (the holding current), such as at the end of a half-cycle of alternating current (AC) mains power.

That's mostly from this page btw, with some other stuff thrown in.

Hope it helps.