Finding Feanor Log

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Earlier this week we talked to our student TA, Will, and he helped us round out the major ideas for our project and helped us troubleshoot our ideas for the functionality of our machine. Our project proposal will be approved soon so we will start to order parts this next week. Although we will most likely not be 3D printing any parts for "Finding Feanor" the lecture this last Friday is helpful in case we decide otherwise. The project seems to be going smoothly with all group members being cooperative and working productively together and separately.


  • After a meeting on Tuesday (9/27) with Will, we realized that our Gantt chart was still a bit too vague to be of much use to use during our various downtimes, such as the period in between the ordering of parts and their arrival. Will suggested that we begin designing the circuit for the phototransistors, so Zach and Sam got to work immediately. We should have a computer generated image of the circuit design on the main wiki page before next Friday (10/7). We all have a much more complete understanding of the project timeline after this week.
  • We all feel a bit more informed after a meeting with Humberto yesterday (9/29) where we decided that our project would include a solar panel after all. We are very lucky as a) there was room in the budget and b) the Arduinos supplied by the lab each have 6 analog/digital converters which should be more than enough for our system.
    • It was also decided at this meeting that our base and rotating frame would be 3D printed rather than made from metal/wood. We all have minimal CAD experience so designing the components may take some more time than anticipated but the magnitude of that delay is still unsure. Regardless, the Gantt chart will have to be updated to reflect this.
  • The budget was also made more concrete than our last update. While we already had the essential components figured out, a solar panel was added along with the necessary connectors and cables for the Arduino and stepper motor driver. The total cost is now $101.98 out of a $150 budget.

Goals for next week

    • Begin CADing the the frame/platform/mounts for the panel/phototransistor unit.
    • Order components. (PRIORITY)
    • Overhaul Gantt chart to reflect our lost time higher understanding of our task timeline.


  • The components have been ordered and the Gantt chart updated. The arrival dates are scattered between Wednesday and Saturday next week.
  • Humberto raised the point that the phototransistor array would not likely give a sufficiently accurate estimation of the incident light angle for fine-tuning our motor steps. He and Zach discussed the possibility of using the panel's output as an additional sensor. The system can then be understood in terms of two phases:
    • The phototransistor array would initialize some 'optimal' angle.
    • Once the motors rotate the panel to that angle, the output of the panel would be measured as it makes small angle adjustments in all four possible directions. If the panel's output does not increase during the angle adjustments, then the angle truly is optimal.
  • The CAD process has begun. The top priority is the array housing; it will be much easier to see what sort of algorithm we will need to develop once the circuit can be combined with the hardware.
  • We have decided to reorganize into project leads:
    • Zach - Algorithm and Programming
    • Sam - Circuit Design
    • John - Mechanical Design

Goals for next week

    • Have transistor array housing printed
    • Design impedence matching circuit to measure panel output


  • As of today, the components that have arrived are the photo-transistors, the stepper motors, and the circuit board. The power adapter and the Arduino stepper motor shield are still on the way.
  • The pyramid for the photo-transistor array and the frame to house the solar panel have been designed in solidworks and are awaiting file conversion and eventual 3D printing.
  • Without the solar panel, we were unable to fully design an impedence matching circuit as we have no way to measure the internal resistance of the panel itself.
    • This will become the goal as soon as the solar panel actually arrives.
  • The next step is to be able to characterize voltage response of the photo-transistors.
    • This will be accomplished by writing a simple Arduino script to read the voltage returned from the phototransistor circuit.
    • The values could then be formatted into a CSV file and exported to Excel for a more thorough analysis.
  • The control algorithm has been written in pseudocode, though needs to be actually implemented in the arduino.
    • The stepper library will be employed to control the stepper motors.

Goals for next week

    • Have the photo-transistors characterized in terms of their voltage response to light stimuli.
    • Have the initial models of the pyramid and frame converted and printed.
    • Determine the step size of the stepper motors (or if it can be controlled) in order to implement in the algorithm.


  • The project is on schedule.
    • The first print of the pyramid turned out exactly right but the frame will need to be redesign to accommodate the keyed stepper motors. The print will be done by next Friday (10/28).
    • Our Arduino code is able to read input from the phototransistors and print a value. The way our circuit is designed, the value of the resistor that sees the Arduino is directly related to the range of values we can read from the phototransistors. We are working to optimize that now.
    • We will need phototransistors of a higher resistance but this shouldn't be too much of set back as one of the group members has enough on hand from a previous project.
  • Components that have not yet arrived:
    • Solar panel
    • Motor driver
    • JST cables

Goals for Next Week

  • Complete new frame redesign and print.
  • Have phototransistor algorithm working and ready for implementation when parts arrive.
  • Begin work towards a prototype to be completed before second project evaluation on 11/4.


  • The team made some big decisions today regarding the mechanical design of the system to better deal with the wires:
    • The stepper motor at the bottom of the frame will now point downward into the base of the system rather than up. This will allow for an arrangement of the wires such that they won't get tangled as easily.
    • The Arduino + motor shield combo will now be housed at the bottom of the frame underneath the panel. This necessitated an elongated frame which was CADed today. Printing will happen this sunday.
  • We have rudimentary control of the stepper motors. Now we can begin the process of implementing the algorithm that will govern our system with input from the phototransistors.
  • Our second project evaluation is scheduled for 11/9. We aim to have a functioning prototype by then so the project pace will start to pick up.
  • Our solar panel still has not arrived.

Goals for Next Week

  • Have new frame completed. Begin assembly.
  • Control algorithm largely worked out.


  • The new frame has been completed, along with a shaft that will allow the motor to turn the panel. Additionally, a full mockup of the assembly was completed in SolidWorks (minus wires).
  • The transistors have been affixed to the pyramid and are able to output a voltage to the arduino that varies according to the intensity of the light and the size of the resistor.
  • An arduino sketch has been created that computes the difference between the four phototransistors and adjusts the steppers based on the difference between the top and bottom and left and right using the arduino stepper library.
  • So far, the power has been supplied through the arduino but a power adaptor has arrived and would allow for the solar tracker to be powered without a computer.

Goals for Next Week

  • Have a semi-working model for the second evaluation.


  • We completed our goal of having a working prototype by Wednesday's midterm project evaluation. The system now takes input from the phototransistor pyramid and drives the two stepper motors accordingly. Currently we have two major issues to fix:
    • The wiring between the Ardunio, shield, and stepper motors needs an overhaul. We are not using any socket connectors right now so the system is incredibly difficult to transport without a wire jostling out of it's pin. On a positive note, the frame is now perfect on it's third iteration and we can begin the process of mounting the components.
    • The control algorithm will need a few tweaks. Right now the stepper motors cause excess vibration because they are being told to move in very small, rapid increments. We will need to figure out a way for the algorithm to tell the motors what angle adjustment is needed as a function of intensity. This will require about a week of test and tune. We would also like to find a way to incorporate information from the panel itself to fine-tune angles after one is initiated.
  • The project is progressing nicely overall. We fully expect to have a working, refined system by the time of the demo (12/6).

Goals for Next Week

  • Have components mounted with wire management problems solved.
  • Begin work on algorithm changes. This will be the last hurdle for the project.


  • Our goal of mounting all components was not completed. Currently the board mounts are on the frame as well as both stepper motors. The panel mount is currently printing. The physical system should be complete by the coming Tuesday (11/22).
  • The angle search algorithm development will have to happen in the week following Thanksgiving. Provided a week with the system we are confident we will be able to have working algorithm for the demo (12/6).
  • For a stretch goal, Dr. Gonzalez suggested that we integrate the power output of the panel as a virtual sensor in order to fine tune the angle. As of now we are unsure we will be able to achieve this goal but we are optimistic.
  • The project is progressing nicely overall. We fully expect to have a working, refined system by the time of the demo (12/12).
  • We have solved the wiring issues we faced in the project evaluation. We are now using clip-in connectors rather than free wires and the wires are bundled so that tangling will be less likely. A redo of the solder job on for the pyramid array is in order.

Goals for Next Week

  • Complete assembly of physical components by Tuesday (11/22).
  • Enjoy Thanksgiving break.