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Flickering stimuli

OS : Win10
PsychoPy version : 1.90.1

What are you trying to achieve?: I’m trying to flicker a letter at 15 Hz.

What did you try to make it work?: I tried to flicker my stimulus using the recommandations here ( My stimulus starts at 0, stops at 2 seconds and I set the the opacity at (frameN % 8) >= 4 to have a flicker function of 15 Hz.

What specifically went wrong when you tried that?: Using the modulo function ((frameN % 8) >= 4) for polygon works well but it does not work for stimtext. Is there any solution to fix it as a code component?
When I try letter.opacity=(frameN % 8) >= 4 in the begin experiment box, I get an error message : "“frameN is not defined”.

Many thanks for your help,


Hi @Laura_Desruez, have you set the update of your text opacity to “set every frame”?