Week 11 - Input devices group assignment

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Measuring the analog levels and digital signals in an input device

In this video, we measure the analog voltage levels across a thermistor that is warmed up (slightly!), you can see the voltage change in real time. A thermistor is a good analog signal to analyse, as initially it's easy to think that the signal is a linear one...a certain temperature change will correspond with a linear change in voltage..but it's not...it's a non-linear response, requiring a Wheatstone bridge to linearise the relationship. Here's a useful guide on this.

In this video, we test the digital signal produced by an active Hall effect sensor. When the magnet is brought close to the sensor, the voltage signal drops to (almost) zero. When it's taken a certain distance away, it steps up to 5 (ish) volts. This process does really highlight that we're not necessarily dealing with EXACTLY 0-5 Volts when dealing with digital signals...hence the values of the pull-up and pull-down resistors really matter. They should be specified/calculated to ensure that the threshold values for the pins are met...ensuring that the correct signal is read!