Bandpass Filter holder

Use of a 430nm bandpass filter improves the beerometer 430nm wavelength resolution to 10 +/- 2nm. Preliminary tests with the bandpass filter showed that using the filter increased absorbance. Beer color measurements are close to the values observed with a commercial spectrophotometer

Design files for the bandpass filter holder are in the Beerometer project on Bitbucket: 

Basically, the bandpass filter is composed of three parts - the 430 nm filter and two 1/4" black acrylic pieces. These are shown in the image below - the upper holder is on the left with the filter and the lower holder on the right. 
The acrylic filter holders have a large cutout for the 430nm filter and a smaller round cutout for the 700 nm LED. 
  • The lower holder part acts as a spacer in this design. It also has cutouts for the resistors on the LED board;
  • The upper holder part is for mounting the filter. The bandpass filter press-fits into acylic.
The acrylic parts are assembled onto the LED board as shown in the top image. Everything is held in place onto the enclosure side using 1" long 4-40 screws and nuts.