Infrared spectrophotometer DIY

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SUMMARY

This discussion focuses on building a DIY infrared spectrophotometer for functional group analysis and compound fingerprinting, specifically targeting the wavenumber range of 4000 to 400 cm–1. Key components include a monochromator for signal splitting and sensors such as thermocouples, thermopiles, or pyroelectric detectors. The conversation highlights the potential of using a bar scanner for signal detection, emphasizing the need for high-resolution models (2000 dpi or more) and the importance of creating a comprehensive database for spectrum peak identification. The referenced build from Hackaday serves as a foundational resource for enthusiasts.

PREREQUISITES
  • Understanding of infrared spectroscopy principles
  • Familiarity with DIY electronics and Arduino programming
  • Knowledge of optical components such as diffraction gratings and lenses
  • Experience with sensor technologies, particularly thermocouples and pyroelectric detectors
NEXT STEPS
  • Research the design and functionality of monochromators for infrared applications
  • Explore the specifications and applications of thermopiles and pyroelectric detectors
  • Learn about building and programming an Arduino to interface with bar scanners
  • Investigate available databases for spectrum peak identification and their costs
USEFUL FOR

Chemistry enthusiasts, DIY electronics hobbyists, and researchers interested in building affordable infrared spectrophotometers for organic compound analysis.

Ludek
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Hello everyone gathered here, I am passionate about chemistry and practical physics but the analysis of organic compounds is beyond my wallet and myself. So I want to build a spectrometer for functional group analysis and compound fingerprinting. The most commonly used range was from 2,5um to 24-25um (Wavenumber 4000 to 400 cm–1) And now the biggest problem will be receiving the signal and splitting the signal to be as monochromatic as possible.That's why I would like to ask how and what to make/buy monochrator. And what sensor would be best, thermocouple or something else
 
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Back in the day when I worked on CO2 lasers (@ 10um), thermopiles, thermistors, etc. were the only practical sensor. IDK, maybe there's something more exotic than just measuring heat now, but it won't be a normal semiconductor junction, especially at 25um.

Check out pyroelectric detectors too. IIRC, they weren't great for average power. OTOH we were at 100's of watts, so YMMV. 25um is still a problem, I think.

Ask Google about deep IR detectors, they'll know more than us, I think.
 
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While it may not work for far infrared a "bar scanner", 1 pixel wide, are DIY. By beam spreading lens and/or mirrors, or just increased distance from the diffraction grating to the bar scanner (reduced intensity) will increase the resolution. It should do near IR okay, and maybe get into the mid IR, depending on brand of bar scanner. Get 2000 dpi bar scanner. Or more, not a 300 dpi or even a 600. Used is cheaper for your first model. Find instructions on several websites/pages. I did. Get a 1 foot bar scanner, not a 1 inch. A discarded page scanner can be disassembled for it's bar scanner. The instructions to make an Arduino to read the bar scanner is online as well.

I think your greatest problem will be creating the database. There are some free ones but they are incomplete. The commercial spectrum peak identification databases are expensive, when I priced them 5 years ago, at over 2,000 USD. At that price, might as well buy the device that comes with the software and database.