Lighting - Results

Initially there was a lot of flicker during the light dimming process. It was obvious the zero crossings were not being properly detected. The input to the mains was switched to a 10Vp-p 60 Hz sine wave from an Agilent 33220 function generator so an oscilloscope probe could be safely connected to the load.

Test setup for the lighting circuit

The test was run and it was shown that the triac was not being fired at the correct time. The triac was being turned on at the beginning of the zero crossing and then waited the a certain length of time (the time the triac was to wait for before firing) before detecting zero crossings again. This caused massive amounts of flickering because the TRIAC fired sporadically as shown in the video and photos.

 

 

After the code was patched flicker was still present. It could be seen on the oscilloscope the TRIAC was not turning off at all zero crossings.

The input filter on the TRIAC was removed which fixed the problem of the TRIAC not turning off. Unfortunately the TRIAC did not always turn on after the input filter was removed. The flicker now is only noticed at the lower dimming stages.