Liquid Transfer Project

The purpose of this project update the Engineering Physics 4A04 Project designed by former students Michael Bulk, Parsian Katal Mohseni, Rachel Poupore, and Andrew Rabeau. By updating the project, the project can be cleaned up and can be used in the future provide a representation of the some of the type of work that students in Engineering Physics complete during their time at McMaster.

In September 2005, the 4A04 students were given the task of designing and constructing a device capable of competing to win four “pouring” races. The races were conducted in groups of two, with the first two races taking place approximately 7 months after the project began, and the final two races being completely a week later. The objective was to fabricate a device that has a minimal cost function, while maintaining maximum fluid transfer from the source to the container. On top of this the task was to be completed in the shortest amount of time possible. The fluid transfer was defined as “removing the contents from the source container and relocating them into the destination container” [1].

The device was constructed such that it was capable of opening either a 351 mL can of pop, a 500 mL bottle of water, or a 591 mL bottle of pop, and transferring the contents into a 1 L plastic container. The device operates on 4 feet by 4 feet and half an inch thick piece of particleboard, which is divided into four quadrants where the source and detection containers can be placed.

The source and detection containers were randomly placed on the playing field, and the purpose of the device was to locate the source container and transfer its contents into the destination container without any assistance, (except for throwing a single switch). The source container needed to be removed from the destination container ensuring that the transfer is complete. The end of the process is noted by the illumination of an LED.

When approaching this project, the first part was to locate the device the group had constructed previously as well as their final report. The device was setup using a clamp instead of screwing it into the particleboard. The report was read such that we became familiar with the project. It was apparent that several pieces of the project were missing, but the main concern was does it function properly using the circuit diagrams the project was inspected, in search for broken or missing connections and parts. Notably there was a missing connection going from an h-bridge to the elevator motor, but this was left as it was for a period of time. The reasoning was the wire looked like it had been intentionally cut and perhaps it was meant to be that way. There were also many open connections and places for the circuit to short, despite the use of electrical tape. All of the electrical tape was removed and heat shrink tubing was used in its place to maintain a more professional look. The motors, LEDs and lasers needed to be checked make sure the entire system was still working. If certain motors are not working, they would need to be replaced, which would be an unwanted hassle. One of the lasers used for detection was missing, and needed to be replaced.

After applying heat shrink tubing to the wires and inspection of the project, the power sources needed to be found and hooked up. These consisted of a 12V DC, 800mA power supply, a 5V DC power supply, two 9V batteries and six 1.5V alkaline cells. The sources were connected in the respective places and the device was turned on. Using the single laser, the rotating motor moved the arm and stopped moving when the bottle broke the signal with the detector. When this occurred the sliding arm moved and stopped when the whisker switch was pressed. This should have enabled the elevator arm to go down and grab the can, however it did not. At this point the circuit had to be revaluated to determine the problem. The wire that we left cut seemed to be the problem, so it was soldered together and the device was tested again. All of the motors worked and none of them needed to be replaced. The main problem now was the missing laser and the alignment of the lasers. Once lasers were acquired they were placed in the holders and aligned. The alignment was difficult and tedious; sometimes when they appeared to be aligned they still would not be detected. Two LEDs were added to the laser detection circuit to verify when the lasers are properly aligned. When the laser is aligned the LED emits red light, and when the beam is broken the LED turns off, this gives a precise indication of what is going on during the device operation.

At this point the device runs off 6 separate power supplies, the 12V source, the 5V source, the two 9V batteries, and the several 1.5V batteries inside each laser. The power supplies are to be integrated so that only one supply is used. This process was began be integrating the lasers. The lasers were taken apart by cutting off the outer metal shell. The batteries were removed, and the positive and negative terminals of the lasers were determined. A ribbon cable was used to connect the lasers to each of the 9V batteries in the detection circuits. The first laser that this was tried with did not work. The laser had over heated and such that the optics inside the laser were damaged and could not be repaired. The second and third lasers tried worked well initially. However, there was a noticeable decrease in intensity from the time the laser turned on, caused by excess current resulting in the lasers to overheat. Current limiting resistors were added in series to the lasers to provide a more luminescent output. The lasers now brightly illuminate the two detectors.

The next step in the project update was to get rid of the two 9V batteries which now provide power to both detectors and both lasers. The 9V going into these circuits first goes through a 5V regulator, which seemed odd at the time but ended up being useful for our purposes. The batteries and connectors were simply removed and the 12V from the power supply was connected to the circuits. They grounds were all commonly connected.

The device now operates off of two separate power supplies; the 5V and the 12V. In order to integrate these two power supplies we had to ensure there was enough current going to each of the motors during the device operation. The current across each motor was measured multiple times.