Electronics > Beginners
MOC3041 BTA26 strange behavior
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gj.gj:
Hi,
I am trying to build a fairly simple circuit but it is behaving in a very strange way.
fig2.png is the schematic.
When I connect R10 the triac conducts immediately despite the optocoupler state.
Without R10 the triac does not conduct but the opto is not able to drive it even though the pin 1 and pin 2 are controlled correctly with 10-20mA through the diode.

Any help to troubleshoot is welcome.
wraper:

--- Quote ---When I connect R10 the triac conducts immediately despite the optocoupler state.
Without R10 the triac does not conduct but the opto is not able to drive it even though the pin 1 and pin 2 are controlled correctly with 10-20mA through the diode.
--- End quote ---
You connected the triac a wrong way around. Swap A1 and A2 pins.
matseng:

--- Quote from: wraper on June 02, 2018, 12:04:38 pm ---You connected the triac a wrong way around. Swap A1 and A2 pins.

--- End quote ---
Would that really matter for a four-quadrant triac?
wraper:

--- Quote from: matseng on June 02, 2018, 02:57:14 pm ---
--- Quote from: wraper on June 02, 2018, 12:04:38 pm ---You connected the triac a wrong way around. Swap A1 and A2 pins.

--- End quote ---
Would that really matter for a four-quadrant triac?

--- End quote ---
It matters for any triac. You cannot just switch the terminals around. Voltage on gate should always be applied in reference to A1(MT1) pin.



matseng:
Hmmm... Yes that seems reasonable. It was 35+ years since I read up about the workings of triacs so I forgot most of it - [ Teh old people are stupids ;-)  ].  But it's slowly coming back  to me now.  Thanks.
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