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StimTracker Light Sensors

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  • StimTracker Light Sensors

    Hi there,

    We are attempting to do a study where we use the StimTracker and the photocell light sensor to send an event marker to our LabChart software. In the only directions I can find on how to do this, it suggests placing a dot or square on the side of the screen to mount the photocell over. I originally assumed that this meant that when the dot appeared with the stimulus, the photocell would detect the change in light and send an event marker to lab chart. However, it seems that when the dot is present the photocell is "off" (no light on the StimTracker) and when the dot is absent the photocell is "on" (sending signal to StimTracker). This means that if I program SuperLab to have a dot appear with the stimulus the maker the photocell is almost always on and an event marker will be sent at the stimulus offset rather than onset (when the dot disappears). This doesn't seem right. Am I missing something in terms of getting the event marker to be sent with the appearance of the dot rather than then disappearance?

    Thanks so much!

  • #2
    I think you have used the wrong light sensor. Use the black one for the black background with a white dot, or the white one for the white background with a black dot.

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    • #3
      Are you using SuperLab version 4 or version 5? SuperLab 5 has a built-in feature for displaying a light sensor “patch” automatically with the stimulus.

      Dolly, the phototransistor inside is identical regardless of the cable color. Most experiments have a black background or white background, so we provide the light sensor in these two colors to minimize distraction to participants.

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      • #4
        Hi, thank you for telling me that. But I found that if I use the black light sensor when using the black dot with a white background, the signal from light sensor is always on but is off then the black dot appears. Is that because of the threshold rather than the light sensor?

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        • #5
          The behavior that you describe should happen regardless of the color of the light sensor that you use. If you have a white background, then the light sensor is exposed to light and the blue LED on the front panel should turn on. When the black dot appears, it should turn off.

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          • #6
            Hi there,

            I am using SuperLab version 4 so we had to program a dot to appear with the stimulus. As you noted we found that this worked exactly the same with both sensors (as they are identical).

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            • #7
              As I mentioned earlier, displaying a light sensor patch would be simpler in version 5. Here’s a screen snapshot:

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              • #8
                Thanks so much. However, we don't own SuperLab version 5 - we only have SuperLab version 4. So I have to be able to program within that context. It sounds like my solutions are either to program so that the dot is always present and to have it disappear with the onset of the stimulus so that an event marker is sent or to program with a black background so a white dot appears with the onset of the stimulus. Do these sound like two reasonable options?

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                • #9
                  Yes, they do.

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