Viewing phase angle and Zero cross with Oscilloscope [SOLVED]

Am new when it come to using an oscilloscope. I am trying to adjust the triggering of a TRIAC at the peak of the sine wave using an Oscilloscope.

What i've Tried:
I have ch1 probed on the secondary of my project transformer. The transformer is a PCB transformer, so its isolated. The GND is not connected. On Ch2 i've connected the probe on pin 5 of the Atmel and GND to the negative of the PCB.

So what do you see? By "negative of the PCB" do you mean Arduino ground?

All channels of a 'scope share the same gnd, note.

Yes the pcb GND. The Arduino is on proto board, hence the arduino chip shares the same GND
OSC1.jpg
OSC2.jpg

I don't understand why you are seeing negative waveform on the transformer secondary - it should be
clamped by the bridge rectifier to no more than a diode-drop below GND.

I am probing before the rectification so as to get a sine wave to adjust the firing of the TRAIC at the peak. Well that is my intention.

What is the Trigger type that i should go for in here. Pulse was what is was thinking to use. Are there anything else that i should be looking at ?

anishkgt:
I am probing before the rectification so as to get a sine wave to adjust the firing of the TRAIC at the peak. Well that is my intention.

I know, and you said the scope gnd was connected to the PCB gnd, so I expect to see the
waveform clamped.

Well I’ve got some improvement.

Probed ch1 on pin 4 that is the pin from the optocoupler. ch3 has another transformer secondary probed to but when a pulse is send out ch2 wave form is like the one attached. Why is that ? what sort of wave form is that ?
OSC.jpg

Hi,

but when a pulse is send out ch2

No, the CRO does not send out a pulse, PULSE on your CRO is how it is triggered, get the CRO manual out and learn how its functions work.

Tom.... :slight_smile:

When i said send out i meant, send from the Arduino on Pin5 to the TRIAC driver MOC3023M. Sorry about the confusion :confused:

Hi,

Ch1 is showing the zero crossing points of the waveform in CH3,so that is working.

Connect CH2 to pin5 of the arduino, use 2V/cm vert scale to show pulse.

R12 is your output power I presume, adjust that and see what CH2 shows..

Tom... :slight_smile: