Monochromator

Adjustable Monochromator. A monochromator is a device which takes light and transmits it to into a narrow band of wavelengths. Using a form of mechanical filtering (diffraction) the user is able to select a specific wavelength (color) which would exit through a exit slit. The monochromator holds many scientific applications ranging from measuring a reflected or transmitted light off a surface. By branching two assemblies together, one can produce a excitation wavelength aiming at the second which can analyze the emitted light.

The basis of this project was derived from a early project Bproman and Ajrettig developed based around making an affordable piece of lab equipment. The design used a whole CD which was fixed, thus causing it to struggled to focus the wavelength and the exit slit had to be set manually by sliding a printed shroud. This design used the previous concept with an addition of a rotating reflective surface which aims the wavelength to an exit slit which can be finally adjusted to a desired wavelength.

Previous Design:

New Design:

Bill of Materials

  • PLA Printing Filament (1 kg) - $14.99
  • Blank CD (Can be replaced with any CD) 25pk - $7.79
  • Box Cutter Blade 100 pk - $9.98
  • M3 8mm Socket Head Cap Screws 25 pk - $3.23
  • M3 25mm Socket Head Cap Screws 100 pk - $11.79
  • Ballpoint Pen Spring (any spring) $9.99 100pk -

Download CAD and STLs Here

Tools needed

  • MOST Delta RepRap or similar RepRap 3-D printer
  • M3 Metric Short Arm Allen Wrench
  • Utility Knife -
  • LED Flashlight -

Skills and knowledge needed

  • Monochromator

Technical Specifications and Assembly Instructions

Parts (Qty 1 for all)

  • Body2
  • Body Cover
  • Light Slit Left
  • Light Slit Right
  • Light Reflector Gear

Printing

  • Material: PLA or Equivalent
  • Support: None
  • Layer Height: 0.2mm
  • Printer Speed: Varies based off Model, choose a speed in order to give best print quality
  • Print Temp: Choose based off material selection for best print quality
  • Specific Part Instruction:

Gears

  • Density: 100%
  • Walls: 4

Rest of Components:

  • Density: 15%
  • Walls: 2

Estimated Time - 7 hrs

Installation

Estimated Time - 30 min

  1. Take Left and Right Slit, using 3M 8mm screws attach a box cutter blade to each of the components. See Picture below

  1. Using a 3M 25mm screw feed it through the hole located on the side of the Right Slit part.
  2. Place the pen spring over the screw
  3. Using the guiding rails, secure the left and right slit. (do not over tighten as this is your calibration screw for the the slit thickness)

  1. Carefully using a sharp blade, cut a small reflective piece out of a CD
  2. Glue the reflective surface to the tab on the larger gear. See picture below for arrangement.

  1. Place the gears on their respective shafts of the body component, these should be loose enough to still allow rotation. Clean up as needed based off printer quality.

  1. Place the slit assembly with the body assembly, this should be a tight fit. See picture below for alignment.
  2. Place the Body Cover over the whole assembly lining up the holes.

10. Secure with M3 25mm screws

How To Use/Adjust

  1. Place a light source at the opening, preferably a single white LED source.
  2. Wavelengths can be adjusted by moving the small gear located in the rear of the assembly.

  1. Slit thickness can be adjusted by tightening or loosening the M3 25mm screw located on the side of the slit assembly.

Common Problems and Solutions

Shattering CD - When cutting the CD to size, be sure to use a fresh blade and carefully cut using a straight edge till all the way through the CD.

Reflective Surface - When cutting be careful, reflective surface may flack off or peel. If it occurs cut a new section.

Cost savings

Cost of Production

$0.37 - Gear A + B

$0.22 - Light Slit Left

$0.13 - Light Slit Right

$0.70 - Body Cover

$0.99 - Body

$0.31 - Blank CD

$0.20 - 2x Box Cutter Blade

$0.52 - M3 8mm Screw

$0.47 - M3 25mm Screw

$0.20 - 2x Pen Spring

Total = $4.11

Commercial Equivalent

Newport: $5000-$8000

Edmund Optics - Mini Chrom (Specific Range): $1500

ScienceTech: $5000-$10000

Savings

Mini Chrom Comparison - 364.96%

Standard Edition Comparison ($5000) - 1217%

Benefited Internet Communities

Gathering for Open Science Hardware (GOSH) - - A movement that seeks to reduce barriers between diverse creators and users of scientific tools to support the pursuit and growth of knowledge.

Spiderwort - - A open source group that has released several scientific designs and continues to develop open source kits that could be used in schools, labs and garages.

Open-Labware - - A community that focues on consumer-oriented 3D printers based off the "maker movement" pushing for prototypes of complex products in owns own garage.

PhysicsOpenLab - - A physics based community that openly shares designs for scientific equipment for people to make at home.

SciencetoyMaker - - Focuses on making cheap fun science based toys for children which makes learning fun.

References

  1. Monochromators Wiki Available: https://en.wikipedia.org/wiki/Monochromator.html
  2. Shimadzu Corportaion - Monochromators Fundamentals Available: https://www.shimadzu.com/an/uv/support/fundamentals/monochromators.html#2
  3. Castor Classes Youtube.com - Monochromator Video Available: https://www.youtube.com/watch?v=87-omb2tSv8 .
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