LM324 Soldering Station

[mike_mike]

Hello. I built the attached soldering station and I am encountering the following issue: on the attached screenshots I got the pins 7 (blue) and 8 (yellow). I don't know what is that impulse type of signal on the blue trace. The yellow trace is showing the signal to the driver of the triac (MOC3021) and the blue trace is showing the pin 7 output of the LM324 (differential amplifier).
The inputs of the differential amplifier are in the 0024 (pin 5) and 0026.jpg (pin 6) screenshots.
I am also attaching the signal coming from the triangle wave generator (0028.jpg). The triangle wave output does not look as a triangle, even if I rotate the 1M trimmer.
Could you please clarify this situation ? Is there a problem in the circuit ?

[magic]

Given the almost 50Hz repetition rate of those pulses it's probably something mains-related, although I'm not sure why the pulses from the diffamp output are so sharp.

Perhaps the diffamp output is a result of heater power turning on and coupling a pulse of noise into the sensor wires. As for the turning on of the heater, it would be due to peaks of mains noise received by the sensor wires.

Zoom in and see whether the blue pulse comes before or after the first yellow pulse.

[mike_mike]

It looks like the yellow (pin 8 ) pulse is coming first or at the same time with the blue pulse (pin 7).

[mikerj]

How clean is the output from your triangle generator?  You might want to consider a little bit of hysteresis on U1C to ensure clean switching.