Weekly Reports

Week 12: Nov 17 - Nov 21

We began mounting the optical components onto the base. The construction of a better slit is being tested. A small change to the program was made: the stepping rate of the motor was increased. The physical diode translation unit has been tested with the existing circuit: the result is that there is enough torque. Also, the diode has been mounted to the fly nut. Wires have been chosen to be long enough to not interfere with the motion. During testing it was demonstrated that the diode does translate down the bolt as the motor rotates. An enclosure is still required to prevent ambient light from saturating the photodiode.

Week 11: Nov 10 - Nov 14

All three of the electrical proof of principle tests (the stepper, the photodiode detector, and the RS232) were embedded into one PIC program. The code takes an ADC measurement, displays it on the laptop via RS232, and increments the stepper motor. It continues doing this in an endless loop. Looking at the hyperterminal screen we get a series of numbers that increases and decreases (32, 32, 32, 28, 27, 27, 32…) corresponding to the photodiode readings . This data can be saved onto a txt file, or copied directly onto Excel to produce an intensity graph.

The stage translation component has been placed onto a plywood base. A large plastic gear was attached to a nut using metal/plastic superglue. This nut was screwed onto the extended part of the bolt. If the bolt is tightened, this arrangement is very stable. Further more, a small piece of plywood was fitted for the stepper motor (clearance holes and air ventilation holes were drilled) and it was attached with two small bolts. The piece of plywood was then attached to the base at 90 degrees. A small plastic gear was glued to the stepper motor. The placement of all the items is slightly adjustable, and was fixed at an optimum gear contact position.

Week 10: Nov 3 - Nov 7

A transistor circuit was successfully completed for powering the stepper motor. The bolt was placed onto a metal bracket allowing it to spin freely. Gear to be used were found, and will get glued soon. Successful communication with the computer was attained. We were able to send the photodiode readings to a terminal screen.

Week 9: Oct 27 - Oct 31

The base of the spectometer has been found in the form of an abandoned drawer. The microcontroller has been successfully programmed to perform basic functions. First it outputs 4 different square waves to drive the motor, then it reads the voltage of the photodiode and outputs it on a port. Lastly, some basic logic makes it turn on an LED once it becomes dark around the photo diode. Efforts to communicate with a laptop have begun, with marginal success. Transistors are going to be used to power the motor, but we are still getting this part of the circuit to work.

Week 8: Oct 20 - Oct 24

The optical proof of principle was completed. It was determined that the use of a slit was far more effective than that of a large pinhole. It would be interesting to investigate a small pinhole, but the slit appears to be the best choice. To make the slit, a wooden frame will be constructed with aluminum foil stretched over it. An exacto knife will be used to precisely cut the slit. The slit will be constructed this weekend. Another piece of equipment which is required is a stage for the prism. It will be held in place with tape and rubber bands between two pieces of wood. Light pressure will be applied to keep the prism in place. This will also be constructed during the weekend. Lastly, several other holders will be created out of wood for lenses and other equipment, as well as a stage for the LED's to be tested. On the electrical side, the photodiode was successfully tested, by moving it into the refracted beam, and reading a voltage via an oscilliscope.

Week 7: Oct 13 - Oct 17

We are still waiting for our diode. In addition, we requested a free sample diode from taos. We have purchased a large bolt and several other supplies for the mechanical part of the project. We also began programming the micro controller: we were able to compile some basic code to get the micro controller to output a square wave.

Week 6: Oct 6 - Oct 10

We did not have much time to do work this week. However, we were able to examine the items which were ordered, and chose the lenses which we need. We were able to calculate the focal length of a couple lenses, and investigate how well the LED is colimated with them.

Week 5: Sept 29 - Oct 3

We have found a prism available from the previous year thanks to Ana. We have also finalized the parts to be order. We decided to order just a single Si photo-diode in order to experiment with how well it detects. If it works well we will work on building a good mechanical system. We also chose all the appropriate electronic parts.

Week 4: Sept 22-26

We had several meetings about the design of the spectrometer. The decision was made to go with the prism design, since the grating has an uneven efficiency curve over different wavelengths. To overcome the very narrow spectrum from the prism, we are going to diverge it with a diverging lens. We have also decided to use a single detector, because it would be too expensive to buy or build and array of photo diodes. We will be moving this diode linearly, so a stepper motor will be needed. We have almost finalized the parts we are ordering, and will have it submitted by Sunday.

Week 3: Sept 15-19

On Monday the group had met to brainstorm possible designs. After a discussion we decided that all member were interested in pursuing the Spectrometer and the Free Space Optical Communications System. On Tuesday the group met again and decided to pursue the Spectrometer as the first choice since we were more knowledgeable in the subject. We brainstormed possible designs for our spectrometer and decided to have a draft copy of a proposal prepared for Wednesday. Each group member was assigned to complete a particular section of the draft report. On Wednesday the group held an online meeting and we each shared our concerns, possible problems, and alternate designs. On Thursday the group met to work on the presentation. We had also addressed a problem we were having with the rotating diffraction grating of our design. Finally on Friday we met briefly to practice our presentation and we had presented our topic in front of the class shortly after.

Week 2: Sept 9-12

- We have met on Friday during the lab and discussed some ideas for the projects - We have decided that we want to chose between the spectrometer and the free space optical communication projects. Our plan for this week was too do some independent research and share our ideas via email Sunday evening. We plan to use the wiki page discussion board for future discussions, but it is unfortunately not available to us right now. We have decided to meet on Monday between our classes, and begin writing the proposals.