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Temperature Sensor Reading Explorer

Run the Temperature Sensor Reading Explorer MicroSim fullscreen

About This MicroSim

A TMP36 does not know what a degree is. It produces a voltage, and your code turns that voltage into a temperature:

°C = (V − 0.5) × 100

The sim rewrites that line every frame with the slider's value substituted in, and shows each step of the arithmetic separately. Watching the same number land in the same slot over and over is what makes the formula stick.

Why the 0.5 V offset? Because a sensor running on a positive supply cannot output a negative voltage, and temperatures go below zero. Putting 0 °C at half a volt leaves room underneath: at 0 V the TMP36 is reporting −50 °C. Drag the slider to the bottom and watch it happen.

Why × 100? The sensor changes by 10 mV per degree. There are 100 lots of 10 mV in a volt, so multiplying by 100 converts volts to degrees. Both numbers in the formula are physical facts about the part, not magic constants.

The digital toggle is there for contrast. A DS18B20 or DHT22 does this same conversion inside the chip and hands your code a number, which is why the panel has nothing to show. That convenience costs money, needs a library, and updates only a few times a second. Neither choice is wrong — but a student should know which kind of part they bought.

How to Use

  • Drag Sensor voltage and watch every line of the formula update together.
  • Stop at 0.75 V — the reading is 25 °C, which is why that is the default.
  • Drag to 0 V. The answer goes to −50 °C, which is the whole reason for the offset.
  • Tick Digital sensor instead and see what the same reading looks like when the chip has already done the arithmetic.

Lesson Plan

Bloom level: Apply (L3) -- calculate

Learning objective: Given an analog sensor voltage, the learner calculates the corresponding temperature using the sensor's linear conversion formula.

Before the sim (5 min). Read a TMP36 with real hardware and print the raw value. It will be a number like 15000, which is neither volts nor degrees, and the gap between that and "the temperature" is the lesson.

With the sim (10 min). Work three voltages by hand on paper first, then check each against the slider. Getting it right before looking is the practice; the sim is the answer key.

After the sim (20 min). Write the conversion in code and compare the reading against a thermometer in the room. They will not match exactly, and discussing why — sensor tolerance, self-heating, ADC noise — is a better lesson than a perfect match would have been.

Check for understanding. Ask: "Your code reports 425 °C. What went wrong?" The conversion is being applied to the raw ADC count rather than to a voltage. That single bug accounts for most first-attempt temperature readings.

Embedding This MicroSim

Paste this into any page of the book, adjusting the relative path to docs/sims/ for the page's depth:

<iframe src="../../sims/temperature-sensor-reading-explorer/main.html" width="100%" height="502" scrolling="no"></iframe>

Specification

The full specification below is extracted from Chapter 17: Sensors, Displays, Motors, and Robot Chassis.

Type: microsim
**sim-id:** temperature-sensor-reading-explorer<br/>
**Library:** p5.js<br/>
**Status:** Specified

Purpose: Let a learner adjust a simulated analog voltage and watch the TMP36 conversion formula produce a temperature reading step by step.

Bloom Taxonomy: Apply (L3)
Bloom Taxonomy Verb: calculate

Learning objective: Given an analog sensor voltage, the learner calculates the corresponding temperature using the sensor's linear conversion formula.

Canvas layout: Left (50%) shows a thermometer graphic that rises and falls with the calculated temperature; right (50%) shows the voltage slider, the formula written out with live numbers substituted in, and the final answer.

Interactive controls: Slider for sensor voltage (0.0V-1.5V); a toggle switching between the TMP36 analog formula and a "digital sensor" mode that skips the formula and shows a direct Celsius readout instead, for contrast.

Default parameters: Voltage 0.75V (25°C), analog mode selected.

Behavior: Moving the voltage slider updates the formula's substituted numbers live — "(0.75 − 0.5) × 100 = 25°C" — and the thermometer graphic in real time; switching to digital mode replaces the formula panel with a note explaining that a digital sensor performs this conversion internally.

Implementation notes: p5.js canvas with a text-rendering routine that rebuilds the formula string from the current slider value every frame; simple thermometer fill rendered as a rectangle scaled to temperature.

References