Wemos D1 Mini Web Server based Servo Motor Control

4 min readApr 1, 2021

So far, we have generated the pwm signal in various ways and thus controlled the servo motors. In this tutorial, we are going to do this differently. We will be using a web server run by our Wemos board and we will be able to measure the pwm. Also it will control the amount of rotation of the desired servo motor. In short we will learn about Wemos D1 Mini Web Server based Servo Motor Control.

Materials Required

WeMOS D1 Mini Board [Best Buy]
SG90 Servo Motor [Best Buy]
Jumper Cables [BEST BUY]

SG90 Servo Motor

A servo motor is a type of motor that can rotate very accurately. This type of motor consists of a control circuit that provides feedback on the current position of the motor shaft. This feature allows servo motors to rotate with great precision. Servo motors are classified into different types based on their application, such as AC servo motors and DC servo motors.

Square wave or PWM

Pulse Width Modulation or pwm, a way to regulate electrical power by changing the cut-off time and the connection of the source in each cycle. In fact, pwm is a square signal that can be 1 or 5 volts at a time, or 0, which means 0 volts. For example, if the Duty Cycle of a PWM wave is equal to 80%, that is, in each cycle 80% of the voltage is equal to 5 volts and 20% of the voltage is equal to 0. The PWM is shown in the figure below.

How this project works?

In this project, we first run a web server on port 80 using the Wemos D1 mini board, which uses the ESP8266 chip. We can also customize the page as needed, where we have a slider to change the pwm values. By changing the slider values from 0 to 180 we will be able to control the servo motor connected to Wemos D1 Mini.

Connection Diagram

In this project, we will use one of the pwm pins of ESP8266 board to start the SG90 servo motor. In this case, we will use pin D4, but you can change this part according to your interest and needs by changing a part of the code. Make the connections according to the schematic and the table below.

It should be noted that all IO pins in Wemos except D0 and A0 support pwm, so you can extend this project to a large number to control more servers.

Some More Projects:

Code Analysis

We need to upload the code to start the project, but first we will look at the important parts and sections that need to be explained. We will first call the required libraries. In this project we will use only servo and ESP8266WiFi libraries.

#include <ESP8266WiFi.h>

#include <Servo.h>

In this line, we specify the PIN for connecting the signal wire of the SG90 servo motor with Wemos D1 Mini.

static const int ServoGPIO = D4;

In the following, we introduce the Wi-Fi network information intended for connecting the board.

const char* ssid = "Your WiFi SSID";

const char* password = "Your WiFi Password";

This part of the code is made for the appearance and functions of the web page, which you can change if necessary and customize it to your liking.

client.println(“<!DOCTYPE html><html>”);
client.println(“<head><meta name=\”viewport\” content=\”width=device-width, initial-scale=1\”>”);
client.println(“<title>Servo Angle Controller</title>”);
client.println(“<link rel=\”icon\” href=\”data:,\”>”);
client.println(“<style>body { text-align: center; font-family: \”Trebuchet MS\”, Arial; margin-left:auto; margin-right:auto;}”);
client.println(“.headertext{ font-weight:bold; font-family:Arial ; text-align: center; color: brown ;}”);
client.println(“.slider { width: 500px; }</style>”);
client.println(“<script src=\”https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js\”></script>”);

client.println(“</head><body><h1><u><div class = \”headertext\”> Web Server based Servo Angle Controller</u></h1>”);
client.println(“<p><h3>Angle</h3><span id=\”servoPos\”></span></p>”);
client.println(“<input type=\”range\” min=\”0\” max=\”180\” class=\”slider\” id=\”servoSlider\” onchange=\”servo(this.value)\” value=\””+valueString+”\”/>”);

client.println(“<script>var slider = document.getElementById(\”servoSlider\”);”);
client.println(“var servoP = document.getElementById(\”servoPos\”); servoP.innerHTML = slider.value;”);
client.println(“slider.oninput = function() { slider.value = this.value; servoP.innerHTML = this.value; }”);
client.println(“$.ajaxSetup({timeout:1000}); function servo(pos) { “);
client.println(“$.get(\”/?value=\” + pos + \”&\”); {Connection: close};}</script>”);
client.println(“</body></html>”);

To get the final code click on this link.