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Embedded Systems

The blog

A New Approach (and hopefully a final one)

The Wire Matrix Sensor

or at least so we deem it for now. 

Motivation:

Why do we need a new sensor design?

Cheaper is Better

With the previous sensor design, we focused on reusability with the sensor. Now, we've turned to allowing ourselves to trash the sensor, but with that comes the responsibility of frugality. We need a sensor that is cheaply made, cheaply switched, and cheaply recycled. 

Accuracy Matters

Our error margin is ±5mL, and that's important. With the current implementation, nurses can usually approximate to about ±3mL, so if we're making a digital solution, it needs to have an accuracy that is close to what is currently there. 

 

The Liquid Level Sensor Just Didn't Work

The eTape that we used in the last few blog posts had too many flaws that worked directly against the important factors above. It lacked the CRUCIAL accuracy that we needed, and it was barrenly expensive, so we went back to the drawing board and here's what we've come up with. 


How It Works:

The back plate of the container is perforated with 7 columns of 85 wires. Each of these wires is exposed in the liquid, and a voltage difference is created along the bottom 7 wires by the micro-controller. The highest wire that detects this voltage (because of the conductivity of the liquid) is at the height of the urine. These wires create a matrix that can report the height of the liquid in each column, and because we have only used basic AWG 22 wire, we can throw the entire container away with minimal cost and little material waste. Furthermore, the material of the container and the wire in the back can be recycled with minimal impact to the environment, so we retain the cost efficiency and recyclability while gaining accuracy!

Phillip TrentComment