The project recovered from the delay caused by the machining of parts. It continues on track with mechanical and electrical assembly completed and prototype testing in progress. The updated EVA displays CPI at 0.96 and SPI at 1.05. A project cost reduction was achieved with the structural assembly being finished in fewer hours than planned. This explains the CPI improvement since the last update. The project is ahead of schedule due to the final assembly phase and initial tests being started before the planned dates.

The machining of the trash rack frame parts was finished on March 18. Allowing the mechanical assembly to start. During the mechanical assembly, performed between March 19 and March 21, it was realized that after the purchase phase some changes were made in the design and 25 bolts, and 25 nuts were not ordered. A visit to a hardware store was required to buy the necessary materials. After the purchase the assembly process restarted.

The trash rack requires a solid base for demonstration and proper installation of the motor, sensor, and operator panel. Fabricating a metallic base would increase cost and delay the final assembly's schedule. With the approval of the project manager advisor a ½” thickness plywood board of 15” by 18” was obtained to bolt the components. Figure 1 illustrates the prototype assembled in a plywood board with electrical and mechanical systems integrated.

On the electrical side, one issue arose. Working with two breadboards was causing issues due to a lack of proper space and wires jumping between the breadboards. To solve nonprofessional wiring techniques and eliminate potential malfunctioning, the wiring was moved to one single breadboard. During the initial test, it was realized that the delay required for the conveyor to continue running after the sensor stopped detecting debris was too long. An RC constant recalculation is required to keep the system running only for 8 seconds. This task is in progress. 

The project continues on track with the design phase finished and the manufacturing phase in progress. The updated EVA displays CPI at 0.94 and SPI at 0.97. The CPI indicates the project is slightly over budget due to poor estimation of time required to perform design tasks, which increased the project cost. The SPI depicts that the project is slightly behind schedule due to machining parts being delayed because of machine shop availability. However, electrical tasks were anticipated to keep the project within the SPI limits.

The materials required for mechanical and electrical assembly were purchased on February 22. The 8mm shaft was not available from two suppliers. Therefore, the shaft size needed to be changed from 8mm to 5/16 inches. Figure 1 illustrates the material purchased to build the project.

The logic circuit was wired on the breadboard, and a test to validate the functionality was performed on March 4. The circuit was not working properly. After voltage measurements a flaw in the electrical design was discovered. The logic gates were in an undefined state when a low level signal should be detected. The addition of pull-down resistors solved the problem of grounding the inputs when needed. Additionally, one logic gate malfunctioned. One of the pins responsible for inverting the photoelectric signal was damaged, making it necessary to replace the component. Some resistor values were also recalculated to achieve the desired response from the circuit. Figure 2 illustrates the logic circuit troubleshooting and the functionality test of the switches, the photoelectric sensor, and the DC motor. 

The project is on track with the main documentation being delivered and the initial design started. The EVA was updated, and CPI is at 1.16 while SPI is at 0.92. The CPI indicates the project is below budget because initial tasks took fewer hours than planned to finish. The SPI represents that the project is on schedule due to mechanical and electrical initial designs being delivered on time.

The main concern of the project was if the roller chain and sprockets would work properly. Chain and sprocket SolidWorks model design and 3D printing were prioritized. Initially, six (6) inches of chain links were printed and assembled for design validation. The fit between the pins and the link hole diameter was too tight, leading to the pins breaking easily. A redesign of the pin diameter and undercut dimensions was performed to provide a better fit. After the changes, the new components were printed for another test. The first entire roller chain printed and assembled is shown in Figure 1. Another rework required was to reduce the lightening holes of the large sprocket that were too close to the teeth. This solution is in progress and the new sprocket is waiting to be printed.

On the electrical side, the logic circuit was validated on Tinkercad. A concern arose due to a different voltage required for logic gates, sensors, and DC motors to work. The use of two different power supplies was decided by the team to avoid malfunctioning of the logic gates when the motor activates.