Prototyping

Assembling our prototype

Once we had finalised the design of our rack, we mounted the individual components such as the fans and load sensors to the aluminum profile.

We then recalibrated both load sensors using the same method as before. Based on our setup, the combined readings from both sensors reflect the actual mass of the shirt, so we coded the system to display the total combined mass as the output.

Oscillating movement of shirt

After a discussion with Dr Ho, we decided to replace the belt and pulley system with a pulsing fan setup to simulate the oscillating movement of the T-shirt.

We conducted a crude experiment to estimate the natural oscillating period of a t-shirt hanging in the intended way. By recording the time taken for 10 oscillations, we concluded that the natural period is 1.4s, and that the natural frequency was 0.71Hz.

credits: save my exam

To maximise the amplitude of forced oscillation, the driving frequency should be approximately similar to the natural frequency to achieve resonance. We did this by pulsing air using a fan with a similar period of 1.4s. Since the fan only had 2 states, ON or OFF, we turned on the fan for 0.7s and turned off the fan for 0.7s.

When we adjusted the oscillation frequency to 0.6 seconds, we observed a noticeable change—the shirt’s movement became more inconsistent and less stable.

To further increase the amplitude of oscillation, we placed 4 fans that would turn on and off at opposite times from one another at the same period of 1.4s.

Experimentation

To determine the mass threshold for our load sensor, so that the fans switch off once the T-shirt is fully dry. We tested our prototype using a grey cotton shirt. We chose this particular shirt because the color change between wet and dry was clearly visible, making it easier to monitor the drying process.

 

• after doing the expt for 3 hrs we lost all our data and had to start over again.
• attach results
• also included a screen