DEV Community: S. Nishanth

IoT-Based Environmental Monitoring System with kiwisIOT

S. Nishanth — Mon, 02 Nov 2026 13:47:41 +0000

I was sitting at my desk in Erode, wondering how hot and humid the room was, and I had no good way to find out. A wall thermometer shows one spot and no history. So I built an IoT environmental monitor with an ESP8266, a DHT11 sensor, and the KiwisIoT cloud platform.

Every two seconds, the board reads the temperature and humidity and sends both values over Wi-Fi to a live dashboard. I can check the room from any browser or phone. The wiring takes three jumper wires.

The hardest part wasn’t the code. My first connection failed because the ESP8266 only works on 2.4 GHz Wi-Fi. KiwisIoT handled the cloud side, so I didn’t need a server or database.

circuit diagram

Circuit Connection

Connect the DHT11 to the NodeMCU as follows:


1. DHT11 Pin        NodeMCU Pin Purpose
2. VCC (+)          3V3         Power supply
3. GND (−)          GND         Ground
4. DATA (S or OUT)  D5 (GPIO14) Data

Live Dashboard

project code

const char* ssid = "YOUR_WIFI_NAME";
const char* pass = "YOUR_WIFI_PASSWORD";

const char* topic = "YOUR_DASHBOARD_TOPIC_ID";

#define DHT_PIN D5
#define DHT_TYPE DHT11

DHT dht(DHT_PIN, DHT_TYPE);

KiwisIoT kiwisiot(ssid, pass, topic);

void sendDHTData() {

  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();

  if (isnan(temperature) || isnan(humidity)) {

    Serial.println();
    Serial.println("Failed to read DHT11!");

    return;
  }

  Serial.println();
  Serial.println("---------- DHT11 MONITORING ----------");

  Serial.print("Temperature: ");
  Serial.print(temperature, 1);
  Serial.println(" °C");

  Serial.print("Humidity: ");
  Serial.print(humidity, 1);
  Serial.println(" %");

  String temperatureData = String(temperature, 1);

  kiwisiot.send("0", temperatureData);

  Serial.print("Sent to KiwisIoT Channel 0: ");
  Serial.println(temperatureData);

  String humidityData = String(humidity, 1);

  kiwisiot.send("1", humidityData);

  Serial.print("Sent to KiwisIoT Channel 1: ");
  Serial.println(humidityData);
}

void setup() {

  Serial.begin(115200);

  Serial.println("     DHT11 MONITORING     ");

  dht.begin();

  Serial.println("DHT11 initialized");

  Serial.println("Connecting to KiwisIoT...");

  kiwisiot.begin();

  Serial.println("KiwisIoT initialized");
  Serial.println("Starting temperature and humidity monitoring...");
}

void loop() {

  kiwisiot.run();

  static unsigned long lastSend = 0;

  if (millis() - lastSend >= 2000) {

    lastSend = millis();

    sendDHTData();
  }

  delay(100);
}

Serial Monitor Output

The full project, with the README, wiring guide, and Arduino sketch, is on kiwisiot GitHub link: https://github.com/Kiwistron/KiwisIoTProjects/tree/main/esp8266/004-dht11-kiwisiot

Powered Smart Detection System Using KiwisIoT

S. Nishanth — Thu, 22 Oct 2026 02:39:23 +0000

Title:

I wired an IR sensor to an ESP8266 and watched it on a live dashboard
published: false

tags: esp8266, iot, arduino, beginners

I had an IR obstacle sensor sitting in a drawer and an ESP8266 NodeMCU on my desk. I wanted to see whether I could check the sensor from a browser instead of standing next to the board. This post covers what I built, the three wires it needed, and the two errors that slowed me down.

What it does

Every two seconds the board reads the sensor on pin D7, prints the result to the Serial Monitor, and sends DETECTED or NOT DETECTED to a KiwisIoT dashboard. That's the whole project. It's small on purpose.

Wiring

It takes three wires:

Sensor VCC to 3V3
Sensor GND to GND
Sensor OUT to D7

circuit diagram

The sensor output is active LOW. When something reflects the IR light back, OUT drops to 0. When nothing is there, it reads 1. So the code checks for LOW:

int irState = digitalRead(IR_PIN);

if (irState == LOW) {
  objectStatus = "DETECTED";
} else {
  objectStatus = "NOT DETECTED";
}

I got this backwards at first and the dashboard said DETECTED when my hand was nowhere near the sensor. Checking the raw value in the Serial Monitor fixed it in about a minute.

connection diagram

The sketch

The sketch connects to Wi-Fi, connects to KiwisIoT with a topic ID, and runs a timer in the main loop so nothing blocks:

void loop() {
  kiwisiot.run();

  static unsigned long lastSend = 0;
  if (millis() - lastSend >= 2000) {
    lastSend = millis();
    sendObjectStatus();
  }

  delay(100);
}

I used millis() instead of delay(2000) so that kiwisiot.run() keeps getting called. If you block for two seconds, the connection can drop.

Errors I ran into

Access is denied on the COM port. Windows said the port was in use. The Serial Monitor was still open in another window. Closing it, unplugging the board, and plugging it back in solved it.

invalid head of packet (0x00) during upload. I had the wrong board selected and my USB cable only charges. Switching to a data cable, selecting NodeMCU 1.0 (ESP-12E Module), and holding FLASH while pressing RST got the upload through.

code

#include <ESP8266WiFi.h>
#include <KiwisIoT.h>

const char* ssid = "YOUR_WIFI_NAME";
const char* pass = "YOUR_WIFI_PASSWORD";

const char* topic = "YOUR_DASHBOARD_TOPIC_ID";

#define IR_PIN D7

KiwisIoT kiwisiot(ssid, pass, topic);

void sendObjectStatus() {

  int irState = digitalRead(IR_PIN);

  String objectStatus;

  if (irState == LOW) {

    objectStatus = "DETECTED";

  }
  else {

    objectStatus = "NOT DETECTED";
  }

  Serial.println();
  Serial.println("---------- IR MONITORING ----------");

  Serial.print("IR Sensor Value: ");
  Serial.println(irState);

  Serial.print("Object Status: ");
  Serial.println(objectStatus);

  kiwisiot.send("0", objectStatus);

  Serial.print("Sent to KiwisIoT Channel 0: ");
  Serial.println(objectStatus);
}

void setup() {

  Serial.begin(115200);

  Serial.println();
  Serial.println("     IR OBJECT MONITORING     ");

  pinMode(IR_PIN, INPUT);

  Serial.println("IR sensor initialized");

  Serial.println("Connecting to KiwisIoT...");

  kiwisiot.begin();

  Serial.println("KiwisIoT initialized");
  Serial.println("Starting object monitoring...");
}

void loop() {

  kiwisiot.run();

  static unsigned long lastSend = 0;

  if (millis() - lastSend >= 2000) {

    lastSend = millis();

    sendObjectStatus();
  }

  delay(100);
}

Tuning the sensor

The small potentiometer on the module sets the detection distance. I turned it until the LED lit only when something was close, then checked that the dashboard matched.

dashboard output

What I'd add next

A running count of detections, shown as a chart
A buzzer that fires on detection
Deep sleep for battery use

arduino output

The code, wiring diagram, and README are on GitHub. Wi-Fi details and the dashboard topic ID are placeholders, so keep your own values in a local secrets.h file.

If you've built something similar, I'd like to hear how you handled sensor noise.

Obstacle Detection with KiwisIoT

S. Nishanth — Thu, 15 Oct 2026 12:13:28 +0000

title: Measuring Distance with an ESP8266 and an Ultrasonic Sensor, Streamed to KiwisIoT
published: false
description: Build a Wi-Fi distance monitor with an ESP8266 NodeMCU, an HC-SR04 ultrasonic sensor, and a live KiwisIoT dashboard.
tags: esp8266, iot, arduino, embedded

cover_image: REPLACE_WITH_COVER_IMAGE_URL

Ever wanted a live distance reading on a dashboard you can check from any browser? In this project, an ESP8266 NodeMCU reads an HC-SR04 ultrasonic sensor every two seconds, calculates the distance in centimeters, and sends the value over Wi-Fi to a KiwisIoT panel, where it updates in near real time.

The full project, including the sketch, README, and images, is on GitHub: https://github.com/Kiwistron/KiwisIoT-Projects/tree/main/esp8266/003-ultrasonic-kiwisiot

What You Need

ESP8266 NodeMCU (CP2102 or CH340 board)
HC-SR04 ultrasonic sensor
A micro USB cable
Four jumper wires
Arduino IDE 1.8.19 or later
A KiwisIoT account

Wiring

HC-SR04 Pin	NodeMCU Pin	Notes
VCC	VIN (5V)	The HC-SR04 needs 5V
GND	GND	Common ground
TRIG	D1 (GPIO5)	Trigger output
ECHO	D2 (GPIO4)	Echo input

Circuit diagram

Watch out for the ECHO pin. The HC-SR04 outputs 5V on ECHO, but the ESP8266's GPIO pins only tolerate 3.3V. A simple voltage divider (for example, 1 kΩ in series with ECHO and 2 kΩ from ECHO to GND) protects the board. A logic level shifter works too.

code


#include <ESP8266WiFi.h>
#include <KiwisIoT.h>

const char* ssid = "YOUR_WIFI_NAME";
const char* pass = "YOUR_WIFI_PASSWORD";

const char* topic = "YOUR_DASHBOARD_TOPIC_ID";

#define TRIG_PIN D1
#define ECHO_PIN D2

KiwisIoT kiwisiot(ssid, pass, topic);

void sendDistance() {

  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 30000);

  if (duration == 0) {

    Serial.println();
    Serial.println("Ultrasonic: No echo received");

    return;
  }

  float distance = duration * 0.0343 / 2;

  Serial.println();
  Serial.println("---------- ULTRASONIC MONITORING ----------");

  Serial.print("Distance: ");
  Serial.print(distance, 2);
  Serial.println(" cm");

  String distanceData = String(distance, 2);

  kiwisiot.send("0", distanceData);

  Serial.print("Sent to KiwisIoT Channel 0: ");
  Serial.print(distanceData);
  Serial.println(" cm");
}

void setup() {

  Serial.begin(115200);
  Serial.println("   ULTRASONIC DISTANCE MONITOR   ");

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  digitalWrite(TRIG_PIN, LOW);

  Serial.println("Ultrasonic sensor initialized");

  Serial.println("Connecting to KiwisIoT...");

  kiwisiot.begin();

  Serial.println("KiwisIoT initialized");
  Serial.println("Starting distance monitoring...");
}

void loop() {

  kiwisiot.run();

  static unsigned long lastSend = 0;

  if (millis() - lastSend >= 2000) {

    lastSend = millis();

    sendDistance();
  }

  delay(100);
}

How the Measurement Works

The ultrasonic sensor measures distance by timing an echo. The firmware sends a 10 µs pulse on TRIG, then uses pulseIn() to measure how long ECHO stays HIGH. Sound travels about 0.0343 cm per microsecond, and the signal travels to the object and back, so the distance is:

distance (cm) = duration × 0.0343 / 2

Here is the core function from the sketch:

void sendDistance() {

  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 30000);

  if (duration == 0) {
    Serial.println("Ultrasonic: No echo received");
    return;
  }

  float distance = duration * 0.0343 / 2;

  String distanceData = String(distance, 2);
  kiwisiot.send("0", distanceData);
}

The 30000 argument sets a 30 ms timeout, so if nothing reflects the signal, pulseIn() returns 0 instead of blocking the loop. The sketch checks for that and skips the send.

Sending Data to KiwisIoT

The loop() function calls kiwisiot.run() on every pass to keep the connection alive, and sends a reading every 2 seconds using a millis() timer. This avoids delay() blocking the connection work.

void loop() {
  kiwisiot.run();

  static unsigned long lastSend = 0;
  if (millis() - lastSend >= 2000) {
    lastSend = millis();
    sendDistance();
  }

  delay(100);
}

Setting Up the Dashboard

Log in to KiwisIoT and create a new panel.
Add a Label widget to show the reading.
Copy the panel's Topic ID and paste it into the sketch.

The label updates with each reading, and the panel shows Online while the board is connected.

Serial Monitor Output

Open the Serial Monitor at 115200 baud to check the readings locally:

---------- ULTRASONIC MONITORING ----------
Distance: 5.35 cm
[TX] {"0":"5.35"}
Sent to KiwisIoT Channel 0: 5.35 cm

Ultrasonic: No echo received

code output

Troubleshooting

"Access is denied" on upload: Close the Serial Monitor before uploading.
"No echo received" every time: Check the TRIG and ECHO wiring and the 5V supply. Point the sensor at a flat, hard surface.
Unstable readings: Secure the jumper wires and keep the sensor away from walls.
Dashboard not updating: Confirm the Topic ID and that the board is connected to a 2.4 GHz network.

Where to Go Next

Trigger an alert when the distance drops below a threshold
Log readings over time for KiwisIoT's chart widgets
Add more sensors on separate channels

The complete code and setup instructions are in the GitHub repository. Feedback and improvements are welcome.

https://dev.to/harshan_shadow/ir-sentinel-kiwisiot-esp8266-based-real-time-object-detection-4ff1

S. Nishanth — Wed, 14 Oct 2026 13:09:26 +0000

Harshan.M

Oct 14

IR Sentinel KiwisIoT: ESP8266-Based Real-Time Object Detection

#hardware #iot #programming #tutorial

4 min read

Harshan.M

Oct 14

IR Sentinel KiwisIoT: ESP8266-Based Real-Time Object Detection

#hardware #iot #programming #tutorial

4 min read

light monitering system with kiwisIot

S. Nishanth — Fri, 09 Oct 2026 05:23:12 +0000

I’m a second-year computer science student, and I wanted to understand how a sensor reading gets from a small board to a web page. So I picked the simplest sensor I could find, an LDR light module, and connected it to an ESP8266 NodeMCU. It needs only three wires: VCC to 3V3, GND to GND, and AO to A0.

The board reads the sensor value with analogRead(A0), which gives a number from 0 to 1023. On my module the number goes up when it gets darker, which felt backwards, so I flipped it with 1023 - rawValue. Now a bigger number means more light. I then added three labels: 700 and above is BRIGHT, 300 to 699 is MEDIUM, and anything below that is DARK.

Every 2 seconds, the board sends the number and the label to a KiwisIoT dashboard over Wi-Fi. I used two channels, because the gauge needs a number and the text display needs a word, and they can’t share one channel. Seeing the gauge move for the first time when I covered the sensor with my hand was a great moment. A phone torch pushes it to BRIGHT.

A few things tripped me up. The ESP8266 only works on 2.4 GHz Wi-Fi, so the dashboard stayed offline until I checked that. The board also has just one analog pin, so the AO pin on the sensor is the only one that works for a full range of values. The DO pin only gives on or off, so I left it unconnected.

Right now the project only monitors the light and doesn’t switch anything. My next step is to add a relay so a lamp turns on by itself when it gets dark. I also want to add a chart widget to see the light levels over time.

circuit diagram

coding

/*
 * Project: LDR Light Sensor Module with ESP8266 and KiwisIoT
 * Project ID: KIWISIOT-001
 * Board: ESP8266 NodeMCU
 * Sensor: LDR Sensor Module
 */

#include <ESP8266WiFi.h>
#include <KiwisIoT.h>

const char* ssid = "YOUR_WIFI_NAME";
const char* pass = "YOUR_WIFI_PASSWORD";

const char* topic = "YOUR_DASHBOARD_TOPIC_ID";

#define LDR_PIN A0

KiwisIoT kiwisiot(ssid, pass, topic);

void sendLightData() {

  int rawValue = analogRead(LDR_PIN);

  int lightLevel = 1023 - rawValue;

  String lightStatus;

  if (lightLevel >= 700) {
    lightStatus = "BRIGHT";
  }
  else if (lightLevel >= 300) {
    lightStatus = "MEDIUM";
  }
  else {
    lightStatus = "DARK";
  }

  Serial.println();
  Serial.println("---------- LIGHT MONITORING ----------");

  Serial.print("Raw LDR Value: ");
  Serial.println(rawValue);

  Serial.print("Light Level: ");
  Serial.println(lightLevel);

  Serial.print("Light Status: ");
  Serial.println(lightStatus);

  kiwisiot.send("0", String(lightLevel));

  kiwisiot.send("1", lightStatus);

  Serial.print("Sent to KiwisIoT Channel 0: ");
  Serial.println(lightLevel);

  Serial.print("Sent to KiwisIoT Channel 1: ");
  Serial.println(lightStatus);
}

void setup() {

  Serial.begin(115200);

  Serial.println();
  Serial.println("    LDR LIGHT MONITORING    ");

  pinMode(LDR_PIN, INPUT);

  Serial.println("LDR initialized");

  Serial.println("Connecting to KiwisIoT...");

  kiwisiot.begin();

  Serial.println("KiwisIoT initialized");
  Serial.println("Starting light monitoring...");
}

void loop() {

  kiwisiot.run();

  static unsigned long lastSend = 0;

  if (millis() - lastSend >= 2000) {

    lastSend = millis();

    sendLightData();
  }

  delay(100);
}

Working Prototype

output

my github link:https://github.com/snishanth09122007-bit/light-monitoring-/blob/main/README.md

official Kiwisiot project Github link:https://github.com/Kiwistron/KiwisIoT-Projects/tree/main/esp8266/001-ldr-kiwisiot

The full code, circuit diagram and setup steps are in my GitHub repo. If you’ve built something similar, or have ideas for the relay part, I’d like to hear about it in the comments.