Thinking of an experiment.

The performance of the system has been assessed. It is vibrating quite a bit as well as producing noise at the same time. These should be refined.

A platform was to be built to carry out the experiment, it is to move up and down vertically and vibrate to stimulate the motion of an ambulance on the road. An external force sensor is required to measure the force output by the end of the probe with respect to the platform/phantom surface. It gives a guideline and serves the purpose of assessing the performance of the system. From there, refinements could be done.

PCB Prototype Board

I have been trying to move my circuit from the breadboard onto a piece of prototype board. It is a more secure and permanent solution than a breadboard, it would also give me more freedom on positioning the circuit. As I transfer the components onto the board, the range of load cell read by the microcontroller decreases, whereas the range at the output of the amplifier remains the same. I have tried to rearrange the layout, taken all components out and put them back onto the breadboard to see if any component is burnt during soldering. The reason for this change is unknown yet.

Heat Sink Materials

As operation time of the system increases, heat produced by the motor adds up. The higher the input power, the hotter the motor gets. The specification sheet of the motor specifies that the maximum surface temperature could reach to 80 degrees Celsius when on full power, even though we might never apply that much power to the motor, the hotness could still be felt from the outer surface of the cover. In order to reduce the residual heat, heat sink materials are explored.

Common heat sink materials are copper, aluminium and ceramic, they are normally designed to a comb shape to increase the surface area thus efficiency. Ceramic seems to have a better performance with a thermal resistance of around 10 degree. Whereas performance of copper and aluminium are similar, ranging form 1 to 8 degrees depending on the surface area. Other advantages of ceramic hear sinks over metallic ones is that it is resistive to electricity with very low thermal capacity and light weight.

http://uk.farnell.com/amec-thermasol/mpc252525t/heat-sink-ceramic-25-25-2-5-std/dp/1892475

Ultrasound with Silicon Phantom and Water Balloon

In order to find the most suitable material/s to conduct a test with a sonographer, I carried out a little experiment with the 2D ultrasound machine.

Firstly I have tried to examine the FAST phantom, however as the objects lies quite deep from the surface, nearly no change in shape can be observed.

I have than tried with a balloon filled with water, by placing it on top of a flat silicon surface, a trapezium shape could be seen. As I apply some force to the balloon, the height of the trapezium become smaller. The problem is that as there is no constrains of motion of the balloon, only a low level of force can be applied before the balloon rolls away.

No Force Applied

Slightly Pushed

In order to test the water balloon "phantom" with a larger force to see a higher degree of change in shape, I have sandwiched it into two slices of silicon with a hollow space in between. The bottom slice has a "W" shaped hollow space, when no force is applied, the two sides of the "W" is not in contact with the surface, where as the force increases, the "W" would move towards the surface until the middle ditch of the "W" nearly touches the surface.

No Force

Slightly Pushed

Moderate Level of Force Applied

As the shape of water balloon is a ball, the change in shape is less noticeable. If a irregular shaped balloon such as an animal shaped is used, the change might increase to a greater extent.