Triac circuit issue (weird behavior)

[siongboon]

Hi,

I have duplicate quite a number of triac circuit before.
The recent one I did behavior not quite what I expected.

I have attached the schematic.

What I did is that I added the indicator circuit on the right side,
to indicate if there is AC power at the output.
When connected, I observe a weak lighting up.
I then measure the output which reads about 120Vac.
My AC mains voltage is 230Vac.

I have change a number of new triacs and opto-triac IC.
The fault is the same.
Then I found out the if both the capacitor is removed,
the problem is resolved.
If I add the cap, I cannot put the indicator.
If I put the indicator, I have to remove away the cap.
I am still figuring out why.

Hope that you can advise me on this issue.

I have also tried another indicator lamp that I purchase.
The lamp has a resistor integrated inside.
When connected, the behavior is the same.

Thank you for the help.
Attached is the schematic.

 

[Kripton2035]

please verify that the optotriac is between the gachette and the A2 pin of the triac
it is not mentionned in your schematic...
regards,

 

[FvM]

verify that the optotriac is between the gachette and the A2 pin

In my understanding, the triac schematic symbol has an unequivocal assigment of A1 (next to G) and A2 (opposite to G). But engineers sometimes forget about it.

I observe a weak lighting up.
...
I have change a number of new triacs and opto-triac IC. The fault is the same.

It's no "fault". It's by design. The snubber circuit, necessary for correct operation particularly with inductive load is causing leak
currents. The triac switch doesn't work when loaded with the indicator circuit only.

The indicator circuit is buggy however. 1N5819 is a 40V zener diode. When connecting the circuit to 230V, the LED will be
most likely damaged. Even with a high voltage rectifier (e.g. 1N4007), you may want to protect the LED by an antiparallel diode.

 

[siongboon]

Hi,

I have check my design.
A1 is connected to the incoming Live.
A2 to the output Live.
I suppose this should be the correct connection.

Does this means that with the capacitor,
the LED light up is normal?

Can I say that with nothing loaded, the indicator lights up.?
Once the inductive load is loaded, the indicator will no longer light up.

I wanted to do an indicator to indicate a functioning live wire at the output.
In this case, do you think if I change the capacitance value,
the schematic should work?

Thank you for all your help and advise.
Siong Boon

 

[FvM]

You should not change the capcitance, if you intend to connect a regular load to the triac switch.