Final Build

The response curve of the chosen diode (solid curve) is shown in Figure 2.

Figure 2: BCS2015G1 Response Curve

The diode will be mechanically moved across the whole spectrum, and will then provide information about position vs intensity. The system in Figure 3 will be used to translate the diode.

Figure 3: Diode Translation Unit

A bolt will be fixed between two structures, free to rotate. A nut will be placed on the bolt, restricted from rotation by a guiding rail. When the bolt rotates, the nut cannot and is forced to translate along the bolt. The bolt is rotated by a stepper motor, which is controlled by the microcontroller. The stepper motor rotates 7 degrees per step, and so the motion of the diode is very fine. Roughly 51 steps will produce one rotation. The bolt used for this set up is coarse thread, which means there are 16 threads per inch [1]. One inch is 2.54 cm, and so (51 x 16)/2.54 ~ 321 steps will translate the diode by 1cm.

Figure 4: Translation Stage

The translation stage is shown in Figure 4. The diode is fixed to the wing nut using super glue and duct tape. The guiding rail is the wooden structure with two bolts in it. The motor is fixed in a vertical position to the wooden block at the left. The prism is fixed in place by two wooden blocks, which compress it slightly using two long bolts. The base block is long enough to allow attachment to the base of the unit using several screws. Figure 5 illustrates the fixed prism.

Figure 5: Prism Mounting Fixture

The slit was constructed using aluminum foil and scotch tape. Two rectangular pieces of aluminum foil were cut out, and folded to create a straight edge. These two pieces were then taped onto more aluminum foil to create the slit. This construction was placed onto a wooden fixture, shown in Figure 6.

Figure 6: Aluminum Foil Slit and Diodes

The mounting system for the lens is described in the Optical Proof-of-Principle section. The final version was reinforced with duct tape, and screwed onto the base of the instrument in the correct location. Once the lens was in place it was crucial to touch it as little as possible to avoid unnecessary translations. Figure 7 shows the lens with respect to the slit and the prism.

Figure 7: The Slit, Lens, and Prism

The schematic of the final design is shown in Figure 8.

Figure 8: Schematic of Spectrometer

The dimensions in the above figure are as follows: A 6.5 cm B 9.5 cm C 30.0 cm L 64.0 cm W 39.0 cm

The final version of the spectrometer is shown in Figure 9. The whole spectrometer enclosure can be covered by a piece of cardboard to prevent ambient light from entering.

Figure 9: Final Spectrometer Construction