I am working on a project to control AC load using TRIAC TRIAC AC control

In normal operation it working complete fine

But when a fan regulator specifically step type capacitor regulator is used in vicinty the TRIAC gets triggered and load connected to it which is CFL flikers

After testing I found following observation

The problem only occurs with capacitor type regualtor and not with TRIAC type fan regulator

so my question is how could I reduce the noise (that as per my knowledge is electrically fast transient correct me if i am worng) from Fan regulator.

Please suggest a way to reduce this noise.

Thank you in advance.

  • \$\begingroup\$ Hey Sunil, were you able to find a solution to this issue. I have a similar issue here. What I believe is that triacs don't perform well with capacitive loads. I think we both are having similar issues. Let me know if you find a solution. \$\endgroup\$ Feb 29, 2016 at 9:19
  • \$\begingroup\$ adding a mov across the TRIAC reduce the flickering around 90% .But still 10% CFL flickers due to noise in entering in MOC. \$\endgroup\$ Feb 29, 2016 at 14:36
  • \$\begingroup\$ hello @Whiskeyjack have you found a way to reduce the noise in MOC i am using MOC3041 \$\endgroup\$ Mar 1, 2016 at 10:10
  • \$\begingroup\$ As far as I know, the noise is affecting triac directly rather than MOC. I am using MOC3021. I have raised bounty on my question. Let's see if someone provides a better solution. \$\endgroup\$ Mar 1, 2016 at 14:08
  • \$\begingroup\$ The problem as two reasons first spurious triggering of triac and moc During my test i confirmed that using MOV spurious triggering of triac is removed but moc still triggers And i am also using the same fan regulator like yours. \$\endgroup\$ Mar 1, 2016 at 14:16

1 Answer 1


You are not "worng". It is most likely that either the opto-triac or, more likely, the BTA16 is being triggered by a transient from the other electrical device being switched on an off.

Triacs are normally turned on by triggering the gate, as in your schematic. They can also be turned on by high \$\frac {dV}{dt}\$ across their terminals and the transient could supply that. The datasheet lists in its features

High Immunity to dV/dt - 1500 V/μs minimum at 125°C. (Page 1.)

Minimizes Snubber Networks for Protection

Despite the snubber comment it looks like you need one. A simple RC type would suffice. Make sure it's rated for your mains voltage. (i.e., Don't expect a DC capacitor to last very long!)

  • \$\begingroup\$ Thanks for reply , i tried using snubber circuit but it give rise to another the problem ,during off state the cfl flickers due to leakage current from from snubber circuit can u recommend a way to minimize this leakage current. \$\endgroup\$ Feb 27, 2016 at 2:37
  • \$\begingroup\$ I prefer to use a filter circuit for mains to reduce the fast voltage transient. \$\endgroup\$ Feb 27, 2016 at 2:45
  • \$\begingroup\$ @transistor can u show me the rc snubber for this ? \$\endgroup\$
    – Jaimin
    Jan 20 at 7:06

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