Real-time sensor dashboard in Raspberry Pi

Introduction

A real-time sensor dashboard shows live data from sensors so you can watch changes as they happen. It helps you make quick decisions based on current information.

Monitoring temperature and humidity in a greenhouse to keep plants healthy.

Tracking air quality in a room to ensure safe breathing conditions.

Watching machine vibrations in a factory to prevent breakdowns.

Checking water levels in a tank to avoid overflow or shortage.

Syntax

Raspberry Pi

1. Collect sensor data using Raspberry Pi sensors.
2. Send data to a dashboard app or web page.
3. Update the dashboard display in real-time using a refresh method or WebSocket.
4. Visualize data with charts, gauges, or numbers.

Use simple Python scripts on Raspberry Pi to read sensor values.

Choose a dashboard tool that supports live updates, like Grafana or a custom web page.

Examples

This Python script simulates reading temperature every second and prints it.

Raspberry Pi

import time
import random

while True:
    temperature = random.uniform(20, 30)
    print(f"Temperature: {temperature:.2f} °C")
    time.sleep(1)

This JavaScript code updates a web page element every second with new temperature data from the server.

Raspberry Pi

<script>
  setInterval(() => {
    fetch('/sensor-data')
      .then(res => res.json())
      .then(data => {
        document.getElementById('temp').textContent = data.temperature + ' °C';
      });
  }, 1000);
</script>

Sample Program

This Python Flask app simulates sensor data and serves it to a simple dashboard web page that can request updates every second.

Raspberry Pi

import time
import random
from flask import Flask, jsonify, render_template

app = Flask(__name__)

@app.route('/')
def index():
    return render_template('dashboard.html')

@app.route('/sensor-data')
def sensor_data():
    temperature = round(random.uniform(20, 30), 2)
    humidity = round(random.uniform(40, 60), 2)
    return jsonify({'temperature': temperature, 'humidity': humidity})

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Make sure your Raspberry Pi has network access to serve the dashboard.

Use simple charts or numbers for clear, quick understanding.

Test sensor readings separately before integrating with the dashboard.

Summary

A real-time sensor dashboard shows live sensor data to help you watch changes instantly.

Use Raspberry Pi to collect data and a web app to display it with automatic updates.

Keep visuals simple and update frequently for best results.

Practice

1. What is the main purpose of a real-time sensor dashboard on a Raspberry Pi?

easy

A. To run heavy data processing tasks offline

B. To store sensor data for long-term analysis only

C. To display live sensor data instantly for monitoring

D. To control the Raspberry Pi remotely

Solution

1. Step 1: Understand the dashboard function

   A real-time sensor dashboard shows live data as it changes, helping users monitor conditions instantly.

2. Step 2: Compare options to purpose

   Only To display live sensor data instantly for monitoring describes displaying live sensor data instantly, which matches the dashboard's main goal.

3. Final Answer:

   To display live sensor data instantly for monitoring -> Option C

4. Quick Check:

   Real-time dashboard = live data display [OK]

Hint: Real-time means showing data as it happens [OK]

Common Mistakes:

• Confusing storage with live display
• Thinking dashboard controls the device
• Assuming heavy processing is done on dashboard

2. Which Python code snippet correctly reads a sensor value on Raspberry Pi for real-time updates?

easy

A. sensor_value = sensor.read()

B. sensor_value == sensor.read()

C. sensor.read = sensor_value()

D. sensor_value := sensor.read

Solution

1. Step 1: Identify correct assignment syntax

   In Python, to assign a value from a function call, use single equals: variable = function().

2. Step 2: Check each option

   sensor_value = sensor.read() uses correct assignment and function call syntax. Options B and C misuse operators or assignment. sensor_value := sensor.read uses walrus operator incorrectly without parentheses.

3. Final Answer:

   sensor_value = sensor.read() -> Option A

4. Quick Check:

   Assignment uses =, not == or := alone [OK]

Hint: Use single = to assign function output to variable [OK]

Common Mistakes:

• Using == instead of = for assignment
• Trying to assign function call incorrectly
• Misusing walrus operator without parentheses

3. Given this Python code snippet for updating a dashboard:

import time
sensor_value = 0
for _ in range(3):
    sensor_value += 5
    print(sensor_value)
    time.sleep(1)

What will be the printed output?

medium

A. 5\n10\n15

B. 0\n5\n10

C. 5\n5\n5

D. 0\n0\n0

Solution

1. Step 1: Analyze the loop increments

   Initially, sensor_value = 0. Each loop adds 5, so values become 5, then 10, then 15.

2. Step 2: Confirm printed values

   Each iteration prints the updated sensor_value, so output lines are 5, 10, and 15.

3. Final Answer:

   5\n10\n15 -> Option A

4. Quick Check:

   Increment by 5 each loop = 5,10,15 [OK]

Hint: Add increments stepwise and print each [OK]

Common Mistakes:

• Printing before incrementing
• Resetting sensor_value inside loop
• Ignoring loop iterations count

4. You wrote this code to update a sensor dashboard:

while True:
    sensor_value = sensor.read
    print(sensor_value)
    time.sleep(1)

Why does the dashboard not show updated sensor values?

medium

A. Because time.sleep(1) pauses too long

B. Because sensor.read is missing parentheses to call the function

C. Because print() does not display values

D. Because while True causes an infinite loop

Solution

1. Step 1: Identify function call syntax error

   sensor.read is a function and must be called with parentheses: sensor.read()

2. Step 2: Understand impact on sensor_value

   Without parentheses, sensor_value stores the function object, not the sensor data, so printed values don't update.

3. Final Answer:

   Because sensor.read is missing parentheses to call the function -> Option B

4. Quick Check:

   Function call needs () to get value [OK]

Hint: Always add () to call functions [OK]

Common Mistakes:

• Ignoring missing parentheses on function calls
• Blaming sleep for no updates
• Thinking print() doesn't show output

5. You want to build a real-time dashboard on Raspberry Pi that updates sensor data every second and shows the average of last 5 readings. Which approach is best?

hard

A. Calculate average once at start, then display static value

B. Store all readings forever and calculate average of all data each second

C. Update dashboard only when sensor value changes, ignoring average

D. Store last 5 readings in a list, update every second, calculate average, then update dashboard

Solution

1. Step 1: Understand real-time averaging requirement

   To show average of last 5 readings updated every second, you must keep a rolling list of last 5 values.

2. Step 2: Evaluate options for efficiency and accuracy

   Store last 5 readings in a list, update every second, calculate average, then update dashboard correctly stores last 5 readings, updates average each second, and refreshes dashboard. Calculate average once at start, then display static value is static, C ignores averaging, D is inefficient and grows data indefinitely.

3. Final Answer:

   Store last 5 readings in a list, update every second, calculate average, then update dashboard -> Option D

4. Quick Check:

   Rolling average needs recent 5 values updated regularly [OK]

Hint: Keep fixed-size list for rolling average updates [OK]

Common Mistakes:

• Calculating average only once
• Ignoring rolling window for average
• Storing unlimited data causing slowdowns