Note: Solved, I posted my reply/answer
I am working on this circuit, where I try to control the fire angle on a Thyristor, using a Diac:
It was a success on lower AC voltage (20Vrms) but once I tried higher voltages, could not get the results that I wanted. I don't know if my probing is wrong (I really do not know where to plug the GND of the probe, even though my setup is isolated from Mains) or if there is something wrong with my circuit.
I believe it is bad scope probing. Here is why. First, just a look on the pcb/Heater and my probes: (These 3 green pcbs are on-the-go-changing-resistors, Chinese stuff)
- I don't give any signal (0V) on MOC3020's input/Anode. This is what I see from the oscilloscope:
Note: I know in reality that no current flows through the heater/78Ohm resistor, since it does not get hot at all.
When I give no signal to the MOC3020, No matter where I hook up the GND probe, those three always show the full sine wave. (I use 1Mohm in series when connecting the GND probe anywhere on the AC)
- When I try to control the fire angle, I see this:
Which does not make sense to me.