Problem with power controlling circuit using MOC3021 and TRIAC

Hi there,
I am trying to design a power controlling circuit for a pump engine (consider as inductive load) as figure below

I use a pulse source to simulate output of the Arduino (5V - 100Hz). The problem is every time I run the simulation, the output of the MOC looks like wrong. The sine wave should be chopped at some points instead of a full wave.
The source is 325V Amplitude, 50Hz. U2 is 500 Vdm, 50mA Igt and 6A I max. R3 & C2, R4 & C1 are used for snubbing.
Can anyone tell me where I made mistakes?
Thanks,

Hi,

there is no GND reference on the right circuit side.. therefore the scope has no reference --> the shown voltage is almost random.
Place a GND symbol to the right circuit side.

Klaus

KlausST said:

Hi,

there is no GND reference on the right circuit side.. therefore the scope has no reference --> the shown voltage is almost random.
Place a GND symbol to the right circuit side.

Klaus

Click to expand...

Thanks for your quick reply.
After placing a GND, the waveform become like this

It's still wrong, right?

Hi,

In another thread I wrote:
Use a pencil and a sheet of paper and draw what you expect ... before you connect the scope.

If you are not satisfied with the shown scope picture...tell us what you expect.

Hint: use a third scope input and show the voltage across your laod.

Klaus

Go to the following web page,
https://www.futurlec.com/LED/MOC3021a.shtml

and on the datasheet's figure 9, check out for yourself the differences between your schematic and the datasheet's schematic.

KlausST said:

Hi,

In another thread I wrote:
Use a pencil and a sheet of paper and draw what you expect ... before you connect the scope.

If you are not satisfied with the shown scope picture...tell us what you expect.

Hint: use a third scope input and show the voltage across your laod.

Klaus

Click to expand...

I've found a blog of a member. https://tahmidmc.blogspot.co.nz/2013/06/power-control-with-thyristor-phase.html. He has some photos as my wish.

schmitt trigger said:

Go to the following web page,
https://www.futurlec.com/LED/MOC3021a.shtml

and on the datasheet's figure 9, check out for yourself the differences between your schematic and the datasheet's schematic.

Click to expand...

Basically I use the datasheet's schematic to design my circuit. That's why I don't understand why it doesn't work properly!

• R3 and C2 is snubber circuit for the opto-coupler meanwhile R4 and C1 is snubber circuit, protecting the TRIAC.
This is my calculation. Please correct me if I make mistake.