DIY LED Spectrum Analyzer
- Thread starter giulianom
- Start date
Following along! It's would be nice to know, instead of guessing, if the LED's are what the sellers tell us. Thank you for doing this!
Depending on how the "kit" looks like when it arrives, I may decide to redesign a new box to be made out of 1/4" black acrylic.
Has to be black, because the interior of the box needs to be completely dark - except for the light that it lets in through the slit at one end.
The "kit" project uses a VHS tape clamshell box, with some black paper to opaque the container.
Has to be black, because the interior of the box needs to be completely dark - except for the light that it lets in through the slit at one end.
The "kit" project uses a VHS tape clamshell box, with some black paper to opaque the container.
Here's the kit, it arrived today:
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Contents:
<ul>
<li>VHS Clamshell box</li>
<li>Creative Labs 1.3 Megapixel HD Webcam</li>
<li>Black cardstock.</li>
<li>Velcro</li>
<li>A slice of a DVD-R disk.</li>
</ul>The DVD slice acts as the diffuser, to split the beam of light into many slices.
You take the DVD, split the layers apart, and use the lower clear side with the grooves in it, and place it in front of the webcam lens.
Contents:
<ul>
<li>VHS Clamshell box</li>
<li>Creative Labs 1.3 Megapixel HD Webcam</li>
<li>Black cardstock.</li>
<li>Velcro</li>
<li>A slice of a DVD-R disk.</li>
</ul>The DVD slice acts as the diffuser, to split the beam of light into many slices.
You take the DVD, split the layers apart, and use the lower clear side with the grooves in it, and place it in front of the webcam lens.
Making some progress here...
First thing I did was to take apart the webcam, to get down to the circuit board.
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Next, I unscrewed and removed the square ABS plastic lens housing.
Using a hot-air heat gun (350F), I heated up the black aluminum lens housing, and un-screwed it from the square ABS plastic housing.
Heat was necessary because the threads of the lens housing were sealed in place using thread lock glue - which loosens up with heat.
At the bottom of the lens was the UV filter, which had to be removed so that the light spectrum wasn't limited to just visible light.
Here's the bare CCD sensor on the board, with the intact UV filter above it.
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I re-attached the lens assembly minus the UV filter back onto the board.
Since the lens body had been removed, I had to readjust the lens focus, by screwing the lens body in/out - best done with some heat, and some needlenose pliars.
Here is a shot of the camera board with heat shrink tubing protecting the fragile connector wires.
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I followed that up by putting the entire body in some 3/4" heat shrink tubing. I stuck the PCB inside the tubing, shrunk it down some, then cut a hole for the lens.
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Covering the board is important - it blocks light from entering the back side of the board, which the CCD sensor will detect as a shadow - I saw shadows from the PCB circuit traces on the back side!
Here's the VHS clamshell box.
I took a chisel and shaved down the plastic bits on the inside of the case.
The wooden block is just a piece of pine, but cut so that the slope is at a 40 degree angle.
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The last piece - which I can't easily capture on camera - is a sheet of holographic diffraction material.
Basically, it's a sheet of thin transparent plastic with 500 lines per millimeter</em> etched into the plastic - its purpose is to take the incoming light, and diffract/diffuse it into the seperate bands of color.
I got a 6" x 12" sheet of it, and really onlly need about a 1" square.
That piece of diffraction plastic will go over the webcam lens.
Next, I will cut a slot into the end of the VHS clamshell box, to let the light in - that light will enter the box, and hit the camera lens at the 40 degree angle, and the plastic sheet will split it out into the color bands.
First thing I did was to take apart the webcam, to get down to the circuit board.
Next, I unscrewed and removed the square ABS plastic lens housing.
Using a hot-air heat gun (350F), I heated up the black aluminum lens housing, and un-screwed it from the square ABS plastic housing.
Heat was necessary because the threads of the lens housing were sealed in place using thread lock glue - which loosens up with heat.
At the bottom of the lens was the UV filter, which had to be removed so that the light spectrum wasn't limited to just visible light.
Here's the bare CCD sensor on the board, with the intact UV filter above it.
I re-attached the lens assembly minus the UV filter back onto the board.
Since the lens body had been removed, I had to readjust the lens focus, by screwing the lens body in/out - best done with some heat, and some needlenose pliars.
Here is a shot of the camera board with heat shrink tubing protecting the fragile connector wires.
I followed that up by putting the entire body in some 3/4" heat shrink tubing. I stuck the PCB inside the tubing, shrunk it down some, then cut a hole for the lens.
Covering the board is important - it blocks light from entering the back side of the board, which the CCD sensor will detect as a shadow - I saw shadows from the PCB circuit traces on the back side!
Here's the VHS clamshell box.
I took a chisel and shaved down the plastic bits on the inside of the case.
The wooden block is just a piece of pine, but cut so that the slope is at a 40 degree angle.
The last piece - which I can't easily capture on camera - is a sheet of holographic diffraction material.
Basically, it's a sheet of thin transparent plastic with 500 lines per millimeter</em> etched into the plastic - its purpose is to take the incoming light, and diffract/diffuse it into the seperate bands of color.
I got a 6" x 12" sheet of it, and really onlly need about a 1" square.
That piece of diffraction plastic will go over the webcam lens.
Next, I will cut a slot into the end of the VHS clamshell box, to let the light in - that light will enter the box, and hit the camera lens at the 40 degree angle, and the plastic sheet will split it out into the color bands.
I picked up a SERPAC Project Box from Fry's today, and made some progress.
The box is a black ABS plastic clamshell box, the SERPAC model A42:
http://www.serpac.com/a42.aspx">http://www.serpac.com/a42.aspx</a>
The top and bottom half are held together by screws, and the front/rear panels are removable.
[IMG]http://i.imgur.com/ZJnx3.jpg>
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You can see the pin hole I drilled at one end - this lets the light in.
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Back panel, with a notch for the USB cord.
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And finally, here is the first real sample - even though the color arrangement is backwards.
http://spectralworkbench.org/spectra/show/126">http://spectralworkbench.org/spectra/show/126</a>
This was taken from one of my 50W 20,000K LED panels, with the pin hole about 4" away from the LED.
I'll need to open it up and flip the holgraphic diffraction material around so that the color bands go from left to right instead of right to left.
Next is to get a store-brand CFL lamp, and see about finding some Mercury peaks for calibration.
The box is a black ABS plastic clamshell box, the SERPAC model A42:
http://www.serpac.com/a42.aspx">http://www.serpac.com/a42.aspx</a>
The top and bottom half are held together by screws, and the front/rear panels are removable.
[IMG]http://i.imgur.com/ZJnx3.jpg>
You can see the pin hole I drilled at one end - this lets the light in.
Back panel, with a notch for the USB cord.
And finally, here is the first real sample - even though the color arrangement is backwards.
http://spectralworkbench.org/spectra/show/126">http://spectralworkbench.org/spectra/show/126</a>
This was taken from one of my 50W 20,000K LED panels, with the pin hole about 4" away from the LED.
I'll need to open it up and flip the holgraphic diffraction material around so that the color bands go from left to right instead of right to left.
Next is to get a store-brand CFL lamp, and see about finding some Mercury peaks for calibration.
Using a 20W 2700K compact flourescent lamp (CFL), I extracted this spectra for purposes of testing the calibration...
http://spectralworkbench.org/spectra/show/142">http://spectralworkbench.org/spectra/show/142</a>
However, I think the numbers are off, or backwards.
I thought blues were in the 450 range, and reds in the 600 range...
That's not what the calibration test appears to be showing...
http://spectralworkbench.org/spectra/show/142">http://spectralworkbench.org/spectra/show/142</a>
However, I think the numbers are off, or backwards.
I thought blues were in the 450 range, and reds in the 600 range...
That's not what the calibration test appears to be showing...
Success!
I've managed to get the meter moderatly calibrated against a normal CFL - to within 2-3 nanometers, give or take.
Here's the first attempt - this one was wrong because the camera was on the wrong side, and so the colors were reversed.
The angle is 40 degrees from horizontal, and it didn't matter whether the angle was 40 degrees up, or 40 degrees down...
The camera board is zip-tied to a short piece of 1/16" x 3/4" anodized aluminum angle, and the aluminum is epoxied to the ABS plastic case.
The Wrong Way
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I went out and got another project box, since epoxied aluminum can't easily be removed from... well, anything.
I cut a new piece of aluminum, shorter this time so it could be mounted further down in the project box - farther away from the aperture.
You can see the aperture at the top, it's a vertical slot, which is then covered by 2 pieces of black posterboard to form a slit's edges, and another two horizontal pieces to form the slit's ends. They're glued on with rubber cement, easy to remove if I hork something up...
The Right Way
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And finally, a comparison:
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I can bring the meter to the ARC meeting on Tuesday if anybody's interested in checking it out.
I've managed to get the meter moderatly calibrated against a normal CFL - to within 2-3 nanometers, give or take.
Here's the first attempt - this one was wrong because the camera was on the wrong side, and so the colors were reversed.
The angle is 40 degrees from horizontal, and it didn't matter whether the angle was 40 degrees up, or 40 degrees down...
The camera board is zip-tied to a short piece of 1/16" x 3/4" anodized aluminum angle, and the aluminum is epoxied to the ABS plastic case.
The Wrong Way
I went out and got another project box, since epoxied aluminum can't easily be removed from... well, anything.
I cut a new piece of aluminum, shorter this time so it could be mounted further down in the project box - farther away from the aperture.
You can see the aperture at the top, it's a vertical slot, which is then covered by 2 pieces of black posterboard to form a slit's edges, and another two horizontal pieces to form the slit's ends. They're glued on with rubber cement, easy to remove if I hork something up...
The Right Way
And finally, a comparison:
I can bring the meter to the ARC meeting on Tuesday if anybody's interested in checking it out.
And we have our first valid results!
http://spectralworkbench.org/spectra/show/145">http://spectralworkbench.org/spectra/show/145</a>
It shows three major peaks, at around 455nm (blue), 550 (greenish), and 630 (yellow/orange).
As you can see from the lines, there's a sharp drop off at the beginning 400nm range, so this LED in particular doesn't give off much UV.
http://spectralworkbench.org/spectra/show/145">http://spectralworkbench.org/spectra/show/145</a>
It shows three major peaks, at around 455nm (blue), 550 (greenish), and 630 (yellow/orange).
As you can see from the lines, there's a sharp drop off at the beginning 400nm range, so this LED in particular doesn't give off much UV.
