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I am having a problem with the MOC3043. I have designed a circuit to control a TRIAC for a heater as shown in the figure:

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I used a 1 kΩ resistor on the control side/DC side of the MOC3043. Whenever I connect a load and give an input pulse to the MOC3043, resistor R3 (330 Ω) gets damaged.

I am not able to figure out the reason. Can R1 (1 kΩ) on the DC side be a reason? I have used the same circuit with a MOC3023 and it worked fine. The TRIAC used is a BTA16.

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    \$\begingroup\$ The optocoupler input diode anode and cathode pins are 1 and 2. Pin3 is not used. \$\endgroup\$ Commented Apr 16, 2023 at 16:41

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I replaced the resistor R1 with 200 ohm and now the circuit is in working fine.

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R1 will affect the optocoupler diode current, the optocoupler will fire or not, but cannot burn R3. This issue can be explain if the triac BTA16 pin A2 is not connected, so the load current will flow through the optocoupler and R3. Also a faulty BTA16 triac (not firing) could bring with this problem. Check making a jumper between pins 4 and 6, if R3 burns again.

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