How to Interface a Thermal Printer with ESP32 – Print Receipts, QR Codes & Image

Want to add printing to your ESP32 projects, receipts, invoices, barcodes, even logos—without using a full PC? Using a thermal printer like the PNP-500 with an ESP32 lets you do just that. Thermal printers are popular because they print quietly, need no ink, are simple to interface, and work fast. In this guide, you’ll learn how to wire up a thermal printer to an ESP32, use ESC/POS commands, print text, images, barcodes & much more.

What Is a Thermal Printer & Why Use It?

Thermal printers use heat on special thermal paper to produce text or graphics. Since there are no rollers or ink cartridges, they’re cheaper in maintenance and more compact. You’ll often find them in:

• Receipt printers in shops
• Label printers for barcodes
• Small embedded displays in IoT devices

With ESP32 thermal printer, you can create custom printing applications, say a QR code receipt printer, smart home logs, industrial data logs, and so on.

Hardware You’ll Need

• ESP32 Development Board 
• PNP-500 thermal printer module
• 2 Push Buttons 
• 2-cell Li-ion battery 
• Resistors 

How to Wire the Printer to ESP32

• Use the TTL (UART) interface of the printer. This is simpler than RS232 in many cases.
• Connect the TX/RX pins of ESP32 UART2 to the printer’s RX/TX pins.
• Power the printer from a stable voltage (around 7-9V preferred; 5V works for simple text).
• Optionally, add buttons: one button to move through demo image printing, another for full format/demo prints.

Make sure to use pull-ups on signal lines if wires are long to reduce noise, and common ground.

for more step-by-step tutorial: ESP32 Thermal Printer Tutorial: Interface PNP-500 Receipt Printer with Arduino Code & Circuit Diagram

Applications & Use Cases

Here are some ideas where an ESP32-thermal printer combo can be useful:

• Printing sales invoices / receipts
• IoT monitoring dashboards that print logs spontaneously
• Barcode/QR code tickets or labels
• Smart lockers or access control systems printing QR codes
• Portable printing for outdoor data collection

Raspberry Pi Pico GPS Tracking Project with SIM800L & Neo-6M – Step by Step Guide

The Raspberry Pi Pico makes it easy to create your own real-time GPS tracking system. With just a few parts and some basic programming, you can build a fully functional IoT GPS tracker thanks to reasonably priced GPS and GSM modules.

We'll demonstrate how to construct a Raspberry Pi Pico GPS tracker in this tutorial using:

• Neo-6M GPS module to gather location data in real time,
• cellular communication using the SIM800L GSM module, and
• Data can be sent to the cloud and shown on an interactive map using the GeoLinker API.

After following this tutorial, you will have a GPS tracker that can record and send real-time location updates, even with offline buffering in case of network outages.

Components Required

Component	Description	Quantity
Raspberry Pi Pico / Pico W	Microcontroller (RP2040)	1
SIM800L Module	GSM/GPRS module for internet access	1
Neo-6M GPS Module	For GPS data Collection	1
GPS Antenna	External GPS antenna with SMA/UFL	1
GSM Antenna	External GSM antenna	1
LED	Red, Yellow, Green	3
SIM	2G Capable SIM (Airtel)	1
Jumper Wires, Breadboard	For prototyping	as needed

How Does It Work?

• Neo-6M GPS Module picks up latitude & longitude from GPS satellites and sends them as NMEA sentences.
• Raspberry Pi Pico reads these values over UART and parses them.
• SIM800L GSM Module transmits this data to the internet using HTTP POST requests.
• GeoLinker Cloud API stores the location data and plots it on a real-time map.
• If the GSM connection drops, data is stored offline and automatically synced once the network is back.

This way, no GPS point is lost even in areas with weak coverage.

Applications of Raspberry Pi Pico GPS Tracker

This tracker can be adapted for many real-world uses:

• Vehicle Fleet Tracking – monitor cars or delivery vans in real-time.
• Asset Tracking – keep an eye on shipments, parcels, or equipment.
• Pet Locator – attach it to a collar to track pets.
• Bike/Scooter Tracking – prevent theft and track movement.
• Emergency Alert System – send SOS + live location on button press.

Building a Raspberry Pi Pico GPS Tracker, SIM800L, and Neo-6M GPS is not only affordable but also highly customizable. The GeoLinker library removes most of the complexity, letting you focus on logic instead of low-level AT commands.

GitHub Repository with Arduino Code and Circuit for Raspberry Pi Pico GPS Tracker

SR Latch in Digital Electronics: Working, Truth Table, and Variants

If you are diving into digital electronics, and you might have came across latches. In digital electronics, computers remember things with the help of simple circuits called latches which are the simplest memory elements. They store a single bit of binary data and play a key role in sequential circuits and memory design. One of the most fundamental types is the SR Latch (Set-Reset Latch), which operates with two inputs, Set (S) and Reset (R).

In this article, we will explore what an SR latch is, how it works, its truth table, and the differences between the basic SR Latch, Gated SR Latch, and Clocked SR Latch (SR Flip-Flop).

What is an SR Latch?

The SR Latch is a basic circuit that stores one bit of information. It has two inputs:

• Set (S): Makes the output high (Q = 1)
• Reset (R): Makes the output low (Q = 0)

Once set, the output remains stable even if the inputs are removed, which is why it’s used as a memory element.

SR latches can be built using NOR gates or NAND gates. The only difference is that the NAND version uses active LOW inputs, while the NOR version works with active HIGH inputs. 

Gated SR Latch

The Gated SR Latch is similar to the basic SR latch but includes an Enable input.

• When Enable = 1, the latch responds to S and R inputs.

• When Enable = 0, the output stays unchanged, regardless of inputs.

This provides more control and is often used in situations where the latch should only update at specific times.

Clocked SR Latch (SR Flip-Flop)

When a clock signal is introduced, the SR latch becomes edge-triggered, and is commonly called an SR Flip-Flop.

Here’s how it works:

• S = 1, R = 0 → Q = 1 (Set)

• S = 0, R = 1 → Q = 0 (Reset)

• S = R = 0 → Previous state (No change)

• S = R = 1 → Invalid condition

The clock ensures that the output only changes on a rising or falling edge, making it more reliable for sequential circuits.

Applications of SR Latch

• Basic memory storage elements
• Control circuits in microcontrollers and processors
• Debouncing switches in digital systems
• Building blocks for more advanced flip-flops (D, JK, T)

Static IP on Raspberry Pi Made Simple

 

When working with Raspberry Pi on local networks, the device’s IP address can often change after every reboot or network change. This creates problems while accessing your Pi remotely or connecting it to services. To solve this, assigning a Static IP address ensures your Pi always stays at the same address on your network.

In this guide, you'll learn how to configure a static IP on Raspberry Pi OS using a simple configuration file method. This is useful for IoT projects, web servers, or remote SSH access, where a consistent IP is required.

Steps to Set a Static IP

• Check your current IP using hostname -I
• Edit the DHCP configuration:
• Use sudo nano /etc/dhcpcd.conf
• Add static IP settings
• Save and reboot using sudo reboot

Why Use a Static IP on Raspberry Pi?

• Easy remote access via SSH or VNC
• Ensures consistent device identification in home automation
• Helps when assigning port forwarding on your router
• Ideal for Raspberry Pi running servers or cloud services

Setting a static IP is a small but crucial step for a stable Raspberry Pi network setup. It prevents connection errors and is especially handy in larger home or lab networks. Just make sure the IP address you assign doesn’t conflict with other devices.

Learn to Build Your Own Gas Leak Detector with Arduino – Simple DIY Safety Project

Ever thought about how devices can sniff out gas leaks and keep you safe, without you lifting a finger? That’s where a gas leakage detector comes in. It's a simple yet useful project you can build yourself using Arduino. In this guide, we will walk you through how to make your own gas detection system with all the schematics and code you need to get started.

What is a Gas Leakage Detector?

A gas leakage detector uses MQ-5 gas sensor to identify the presence of combustible gases such as LPG, methane, and smoke in the air. When gas concentration exceeds a certain threshold, it triggers a buzzer and alerts users through a connected display or indicator.

Components Required

To build this project, you will need:

• Arduino Uno
• MQ-5 Gas Sensor
• Buzzer
• LED
• 16x2 LCD Display (with I2C Module)
• Resistors
• Jumper Wires & Breadboard
• 5V Power Supply

Circuit Diagram of Gas Leakage Detector Using Arduino

The MQ-5 sensor’s digital output goes to pin A2, while a buzzer (on A0) and an LED (on A1) provide alerts when gas is detected. A common ground is shared, and you can also power the system using USB or a regular adapter. When gas is detected, the Arduino turns on a buzzer and LED.

Applications of Gas Leakage Detectors

• Home safety and kitchen monitoring
• Industrial gas leak detection
• Smart home automation systems
• Educational electronics and IoT projects

Click here to explore the project in detail: How to Build a Gas Leakage Detector Using Arduino: Complete DIY Guide

RFID-Based Attendance System with Arduino

Keeping track of attendance should not feel like a daily hassle. Whether you are running a classroom, managing a small office, or organizing a community event, a simple, low-cost solution can go a long way. This RFID based attendance system using Arduino reads RFID cards to automatically log check-ins and check-outs, shows updates on an LCD, and stores attendance logs with real-time stamps using an RTC module. It's completely offline and stores data locally, so no need for an internet connection. The total cost is just around $30.

Why Choose Arduino for DIY RFID Attendance Tracker?

Arduino gives you full control over the system’s features without depending on expensive or limited commercial options. The MFRC522 RFID reader is accurate, and combining it with real-time clock and EEPROM modules means your data is both timestamped and safely stored, even during a power cut. Plus, once built, this setup is fully reusable and expandable for future upgrades like IoT integration or door control.

Key Features of RFID based attendance system

• Automated RFID card scanning for both entry and exit
• Real-time timestamp logging using DS1307 RTC
• Local data storage with EEPROM, survives reboots
• LCD display for live updates
• Menu navigation via push buttons or serial monitor
• Customizable card programming with personal data

Components You’ll Need

• Arduino Uno
• MFRC522 RFID Reader
• DS1307 RTC Module (with built-in AT24C32 EEPROM)
• 16x2 I2C LCD Display
• Push Buttons (x2)
• RFID Cards/Tags
• Breadboard, jumper wires, and 5V–12V power supply

Real-World Applications

• Classrooms – Track student attendance and prevent proxy entries
• Offices – Log employee in/out times without manual input
• Gyms & Clubs – Track member usage, ensure hygiene with contactless logging
• Workshops – Monitor visitor entry or workshop sessions
• Healthcare & Industry – Touchless logging for safety zones or shift tracking

This RFID based attendance system using Arduino is a great DIY project for anyone looking to solve a real problem while learning valuable electronics and programming skills. It’s affordable, fully offline, and scalable. Once set up, it can handle real-time check-ins, and you will know exactly how every part works.

Build Your Own Mini Drone Testing Rig with 3D Printing

If you have ever rushed to catch a crashing drone during indoor tests, this one's for you. In this guide, you will learn how to build a Build a 3D Printed Mini Drone Testing Stand, based on the Open Gimbal concept, that keeps your mini drones secure while you test. No more unexpected takeoffs or crash landings.

Why Build a Testing Rig?

• Prevent crashes and protect props and motors
• Fine-tune flight behavior in a controlled environment
• Save money, commercial rigs cost thousands; this one uses only ~$50 in parts

Parts You will Need

3D Printed Components:

• Base, mid‑rings (A&B), outer ring, connectors, drone holder

Mechanical Hardware:

• 603zz bearings ×4

• 606zz bearing ×1

• M6 bolt (50 mm)

• M6 nuts & washers

• M3 bolts (30 mm), nuts & washers

Tools:

• Screwdriver, Allen key, mini pliers

How It Works

1. Base + outer ring are connected via M6 bolt for stability.

2. Mid-rings snap into the outer ring—with or without light sanding—and rotate smoothly.

3. Bearings + M3 bolts hold the mid-rings securely.

4. Drone holder with spacers attaches so your mini-drone can be mounted safely

Assembly Steps

1. Connect base + outer ring using M6 bolt and washers.
2. Insert bearings into outer ring’s edges.
3. Attach mid-rings to outer ring with M3 bolts and nuts (add washers to space parts).
4. Install drone holder, using bearings and bolts, adjust bolt lengths to avoid hitting props.
5. Mount your drone using Velcro or ties—and you’re ready to test

Testing and Tuning

• Mount the drone and spin props at low throttle to check smooth rotation.

• Use the rig to fine-tune flight controls like PID values, free from external influences like wind.

• Test motor/prop combos safely, listening for unusual vibration.

• Diagnose issues by checking clearance and tightening bolts if behavior is erratic

3D models and assembly guides are all open-source and available in the tutorial 

Recommended 3D print settings

• Layer height: 0.2 mm
• Infill: 20–30%
• Supports for overhangs
• Specific orientation files included

You are building a compact, DIY Drone Test Rig that holds your drone securely while allowing free movement on all axes. this project is perfect for safely fine-tuning flight parameters, checking motor thrust, and running diagnostics, without the risk of costly crashes or needing expensive gear.

Ready to get started? Head over to the full tutorial, grab the 3D-print files, and tell us how your test rig turns out.

www.circuitdigest.com   

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Learn How to Send SMS with ESP32 Using SMS API

Forget bulky GSM modules and SIM cards, now you can send real-time SMS alerts with ESP32 using the free SMS API from Circuit Digest Cloud. Perfect for applications like temperature monitoring, motion detection, or door-opening alerts. In this project learn how to deliver instant notifications directly to your phone without any apps, dashboards, and fees.

How It Works

• ESP32 connects to Wi‑Fi using SSID and password.
• It reads sensor data (e.g., temperature via DHT11).
• If a threshold is crossed (e.g., temp ≥ 30 °C), ESP32 sends an HTTP request to the SMS API.
• Circuit Digest Cloud validates your API key and sends an SMS to the linked phone number.

What You Will Need

• ESP32 Development Board
• DHT11 Temperature Sensor (or any sensor of your choice)
• Breadboard + Jumper Wires
• 5V USB Power Supply

Circuit Diagram

Getting Started: SMS API Key

1. Visit Circuit Digest Cloud, sign in or register

2. Generate your free API key (valid for 100 SMS/month)

3. Add recipient phone number(s) via OTP

4. Choose an SMS template (e.g., Template ID 102 for temperature alerts)

Applications of SMS API with ESP32

• Smart Home & Security: Get alerts for critical events

• DIY Prototyping: Fast, hardware-free SMS integration

• Educational Projects: Learn HTTP, JSON, cloud APIs ,  all through ESP32

For a more detailed Explanation and Schematics :  How to send SMS with ESP32 using SMS API

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Complete Guide to Amplitude Modulation (AM)

Amplitude Modulation (AM) is among the earliest and most fundamental methods in wireless communication. It set the stage for long-distance audio broadcasting, taking the place of previous spark-gap transmitters. Whether you are an electronics student or a hobbyist dealing with RF circuits, grasping the principles of AM, both in theory and practice, is crucial. This tutorial will guide you through the concepts of AM, waveforms, circuit design, and testing it using an oscilloscope.

What is Modulation?

Modulation is the process of adding a low-frequency message signal, like audio, to a high-frequency carrier signal. This allows the signal to travel longer distances more efficiently. There are three primary types of analog modulation:

• Amplitude Modulation (AM)
• Frequency Modulation (FM)
• Phase Modulation (PM)

Materials Required

1. BC547 - 1 
2. 7805 - 1 
3. Resistor - 470Ω - 3
4. Resistor - 100Ω - 1
5. Resistor 1KΩ - 1
6. Capacitor - 470nF-2
7. Capacitor - 10pF-1

Amplitude Modulation may be one of the earliest modulation techniques, but its simplicity, educational value, and real-world relevance make it worth exploring. Whether you're preparing for exams, building wireless audio projects, or diving into RF basics, understanding AM is a key milestone in your electronics journey.

For a more detailed Explanation and Schematics :  What is Amplitude Modulation? Complete Guide with Formula, Circuit Diagram & Practical Demo

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Build a Fire and Smoke Alarm with Arduino and SMS Notification

In this DIY project, we’ll show you how to build a smart fire and smoke alarm system using an Arduino UNO R4 Wi Fi, MQ2 gas sensor, flame sensor, and SMS alert functionality. This setup not only detects fire and smoke but also sends real-time SMS alerts to your phone, making it ideal for homes, offices, or small industrial spaces.

How the System Works

This project relies on two key sensors:

• MQ2 Smoke Sensor: Detects smoke or combustible gases like LPG, butane, methane, or hydrogen.
• Flame Sensor: Detects the infrared light emitted by flames.

The Arduino continuously monitors these sensors. When it detects a fire or smoke condition, it activates a buzzer and LED indicators (green for normal, red for alert). Simultaneously, it sends an SMS to a predefined number using circuit digest SMS API over Wi Fi.

Components Required

• Arduino UNO R4 Wi Fi
• MQ2 Gas Sensor
• Flame Sensor
• Buzzer
• Red and Green LEDs
• Jumper Wires and Breadboard
• Power Supply
• Internet connectivity (for SMS alerts via API)

SMS Alert Integration

Instead of using GSM modules, this project leverages the built-in Wi Fi of the UNO R4. By integrating with an SMS API (like Fast2SMS), the system sends out alerts immediately when smoke or fire is detected. This makes the setup cost-effective and more modern.

Applications

• Home and office fire safety
• Industrial safety systems
• Smart IoT-based hazard monitoring
• Remote monitoring for senior care or unattended sites

This Arduino-based fire and smoke alarm is a practical, low-cost project with real-world safety benefits. Its ability to send instant SMS alerts makes it suitable for a variety of smart safety applications. Whether you're a hobbyist or an educator, this is a great project to enhance your IoT and sensor integration skills.

For a more detailed Code Explanation and Schematics :  How to build a Smoke and Fire Alarm System using Arduino with SMS Notification

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