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  • in reply to: my spectrometer build #10550

    Update on my spectrometer build:
    Mounted webcam in a small cardboard box. I screwed cam to side of the box so that it could be rotated. I cut a 2″ hole in the box and inserted the cardboard mailer tube. On the end of the mailer tube is a translucent, white plastic ‘stopper’. I put black electric tape over the stopper to make a thin rectangular aperature. The tube aperature was in line with the webcam aperature. It is hard to describe the angles but they were similar to that recommended in the theremino instructions. All construction was very crudely done.

    I was able to ‘calibrate’ the spectrometer using a CFL buld placed right at the mailer tube aperature. The spectrum was ‘boxed’ by rotating the tube aperature with respect to the webcam aperature and adjusting the ‘Y’ value. It was difficult getting used to the calibration procedure. I found that aligning the low end first was the only way to get the scales aligned at both low (left) and high (right) ends.

    I verified cal using a 650 nm red LED laser : it peaked right at 650! I had some other light emitters and those seemed to match the assumed wavelengths. I measured down to about 395nm

    With very crude construction held together with ‘scotch’ tape, it was difficult to get a measurement. It’s works well with a very bright CFL placed rigth at tube aperature but the 650nm red LED was almost too dim to create a specturm. It appeared very faintly on the software raw spectrum display. It also seemed to depend on the angle of the LED laser beam with respect to the mailer tube.

    However, I was very glad to be able to measure an optical spectrum. This will be very useful! . I would like to know if there is a reliable light source to check measurements below 395nm and perhaps as low as 200nm?

    One last thing. I was wondering if there is an update to the Theremino Spectrometer software and I believe the answer is yes according to the recent posts here.

    Great work guys!

    in reply to: my spectrometer build #10045

    Tried to calibrate the spectrum using a CFL as in the instructions. My displayed spectrum has the same shape but can only align either the 436 or or the 53x (forgot exact number) marker. The whole spectrum ( violet to red) lies on the right side of the ‘box’. I tried to use the start X, end X boxes to center but that didn’t work. I tried moving the webcam in the tube but that didn’t move it to the left much or at all. I can only get the spectrum to rotate.

    I tried to push the webcam farther into the tube but could only push a few inches (50mm) using my fingers. If the webcam is not at the end, I lose sight of it in the Theremino display box and it is hard to manipulate the webcam so that the spectrum displays again.

    Question, is the tube too long?. It is 18 inches which is 457mm. Would shortening the tube move the displayed spectrum to the left on the Theremino display?

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