General Design Process and Philosophy (Part 1)

First and foremost, we had to list down the design considerations for this project. There were a few key areas that helped us narrow down our focus: Functionality: The test rig had to have controlled failures which meant that parts that were not supposed to fail had to be over-engineered! Even if this meant choosing a slightly more expensive motor driver with excessive current sourcing capabilities, there was no competition if the closest rival could fail under normal test conditions. Simplicity: We wanted the design to be simple enough so that even a 1st or 2nd year undergraduate student could understand, even contribute to, the project. To aid this, we also aimed to minimised the number of manufacturing processes undertaken so that a ‘standard’ student would be easily able to pick up what was going on. In keeping this simple, it helps to have fewer components. Therefore we aimed to have multi purpose components where possible. An example of this was using the Arduino platform as it is incredibly diverse and able to carry out many of the necessary functions. Finally, we also tried to keep components reasonably priced. Awesomeness: While this might seem like an odd criteria, we recognised that what we were doing was useful and incredibly cool as well! We wanted to impress anyone who came into contact with this project. This is one of the reasons why we chose to model the truck after actual mining trucks, bright yellow and all! Upgrades: The final factor we kept in mind was future expansions on the test rig. We wanted a rig that future team members could...
ADT Chamber: Preliminary Test Data

ADT Chamber: Preliminary Test Data

Preliminary tests on the operating range and control of the environmental variables within the chambers has been conducted. Results are very positive, with humidity generation and control exceeding expectations, and temperature extremes being easily attainable with no failures. Unfortunately UV output is less than expected. Humidity Control Tests: Humidity control is required for both chambers. For the UV chamber preliminary testing shows that the humidification system can raise the humidity level in the chamber to 80% in under 5 minutes from an ambient of ~35%RH. With the testing parameters used the Humidity system struggled to achieve 90%RH in the given time. The dehumidifier is effective, but slow. It is effective at maintaining a low ambient humidity, but not rapidly lowering the humidity level.   We can see that control is excellent. Achieving tolerances below +-1%RH. Additionally, we can see that the humidifier has minimal impact on the temperature of the system.   For the oven we can see that control is also excellent. Multiple temperatures are yet to be tested.   Temperature Control Tests:  Temperature is being controlled by a simple Bang-Bang control algorithm. A PID algorithm has also been implemented and tested, but results are still poor due to additional parameter tuning required. The graph below illustrates temperature control within the oven with 15 minute set point intervals and no insulation. Insulation has been added since this preliminary test. We can see we easily achieve the required temperature of 120C, and can control temperature within +-2C.  With insulation and a tuned PID it is expected that these results will improve. However, this test confirms the core functionality of the temperature...
Master Wiring Diagram

Master Wiring Diagram

Above is the Master Wiring Diagram. This schematic details all the electrical connections required for the ALT project. Additionally, it labels all the micro-controller pins required. The Arduino Mega is used to process all I/O functions, while the Arduino Yun manages data-logging functionality. Sub-systems have been kept together and connections spaced out to aid debugging. Certain time critical functions are attached to interrupt pins, such as the Door switches and safety resets. Finally, as a fail-safe, certain sensors report to both the Arduino Yun and Mega. This allows either micro-controller to reset the other in case of an error or lock up. Each processor also has control of safety critical functions and can cut power if required, minimizing risk....
Progress Update: Humidification System Design

Progress Update: Humidification System Design

The Requirements Analysis and Design Document has been completed! From this the final designs and schematics of the various subsystems have been completed. In this post we look at some of the details of the Humidification System. Humidification System:  The following block diagram gives an overview of the system and it’s various components. In reality, however, there will be two test chambers connected to other system elements, all controlled through the MCU and the valving. Humidity Generator:  Several different humidity generation schemes were considered, but the final design was chosen based on Reliability, Cost, Portability and Safety considerations. The final design is an active bubble humidifier, which humidifies air by bubbling it through a warm water bath. This design is highly reliable and safe. It can be operated completely on DC voltages and components are easily sourced and cheaply available. Dehumidification:  In order to conduct tests below ambient humidity a dehumidification system is required. After considering multiple dehumidification options a replaceable and recyclable chemical desiccant was chosen. A silica gel desiccant was chosen due to its easy and cheap availability, excellent absorption characteristics and high temperature operation. Humidity Valving:  A single Humidity Generator and Dehumidifier needs to be able to service both test chambers. In order to achieve this a valving system is required to switch airflow as required. High temperature valves are required due to oven operating temperature. The system is also low pressure, requiring direct acting valves. Single way valves were chosen for cost, simplicity and sourcing reasons. Humidification Valve Driver:  In order to control all these valves, an amplification circuit is required to convert the MCU...