Week 10 - Input Device (Depth Measurement)


Posted by Jordan Kennedy on November 21, 2017

This week we had to make an input device.

The input device I intend to make will be apart of my final project and will be updated accordingly.

To prepare I initially copied a touch pad board.

sensor

It didn’t program correctly which means I need to revist it.

However, for my final project I want to discretely be able to measure the water depth as I have shown in the drawning below.

This means I will need more leads and to redraw my board with more inputs to get a usable resolution.

senosridea

I am hoping that the touch pad configuration will be sensitive to water.

Revisiting the Touch Pad (12/05)

I am modifying the touch pad design to serve as a water depth sensor for my tank. My intent for this device is to use water depth as an on/off switch. As water contacts the pad, it completes the circuit. In order to achieve this I need to design to the resitivity of water. The resistivity of water is approximately 200 ohm.m.

Resistance and resistivity are related through the following equation.

resistivity

Drawn below is a simplified version of how each of the touchpads acts as a switch.

voltagedivide

Shown below is my design. It supports 12 inputs. I’m intending to use 10 of them. It can be thought of as 10 on/off switches.

depthsensor