I tried to fix this problem the whole weekend but, after no success I decided to post it here. I would really appreciate any help.

The problem

The Wi-Fi module activates the DC motor and lets it run for 3 seconds, but when the DC motor stops after that 3 seconds, the Wi-Fi module and display don't respond anymore. It only works once. (After I push the reset button the same thing happens.)


What causes this disturbance? Any advice on my circuit? (I included a Fritzing Diagram because I am bad at drawing schematics)

Fritzing Diagram

#include <SoftwareSerial.h>
#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
SoftwareSerial ESP8266(9, 8); // RX = 8 en TX = 9

#define DEBUG true

boolean FAIL_8266 = false;
int LED = 13; // led op 13

int secondeAan = 3000;

String my_AP_SSID = "myID";
String my_AP_Pass = "myPass";

void setup()
  // -- stel led in --
  pinMode(LED, OUTPUT);

  // -- lcd scherm --
  lcd.begin(16, 2);
  lcd.setCursor(0, 1);

  do {
    ESP8266.begin(115200); // start communicatie met esp8266

    //Wait Serial Monitor to start
    while (!Serial);

    lcd.print("--- Start ---");


    if (ESP8266.find("OK"))
      FAIL_8266 = false;
      sendData("AT+RST\r\n", 4000, DEBUG);
      sendData("AT+CWMODE=3\r\n", 2000, DEBUG);
      sendData("AT+CWJAP=\"" + my_AP_SSID + "\",\"" + my_AP_Pass + "\",9,4\r\n", 2000, DEBUG);
      sendData("AT+CIFSR\r\n", 2000, DEBUG);
      sendData("AT+CIPMUX=1\r\n", 2000, DEBUG);
      sendData("AT+CIPSERVER=1,80\r\n", 2000, DEBUG);

    } else {
      lcd.setCursor(0, 1);
      lcd.print("Module have no response.");
      FAIL_8266 = true;
  } while (FAIL_8266);

void loop()
  // Get the number of bytes (characters) available for reading from the serial port
  if (ESP8266.find("+IPD,"))
    lcd.print("Nieuwe connectie");
    // -- sluit connectie --
    sendData("AT+CIPCLOSE=0\r\n", 100, DEBUG);
    sendData("AT+CIPCLOSE=1\r\n", 100, DEBUG);
    sendData("AT+CIPCLOSE=2\r\n", 100, DEBUG);

void motorToggle () {
  digitalWrite(LED, HIGH);
  lcd.print("eten gegeven");
  digitalWrite(LED, LOW);

String sendData(String command, const int timeout, boolean debug)
  String response = "";

  ESP8266.print(command); // send the read character to the esp8266

  long int time = millis();

  while ( (time + timeout) > millis())
    while (ESP8266.available())
      char c = ESP8266.read();
      response += c;

  if (debug)
  { lcd.clear();

  return response;
  • Can the Uno provide 3.3V power for the esp8266? Should have a 3.3V regulator from 5V instead. And a few very large capacitors. This reference might help: iot-playground.com/2-uncategorised/…. Cheers! Dec 20, 2015 at 23:41
  • @MikaelPatel Thanks for the comment! Do you think this causes the disturbance? The esp8266 works fine without the dc motor running Dec 20, 2015 at 23:44
  • Exceeding the 3.3v regulator capability is possibly an issue, yes. You might also put a small ceramic disc capacitor across the motor terminals or one between each terminal and the can. That used to be considered necessary to suppress interference to lower frequency analog RC gear, it may be less so at 2.4 GHz but still isn't a bad idea. Dec 21, 2015 at 0:36
  • Are you sure this is a hardware issue and not a software issue? Can you post some example code? Based on the information provided, it is impossible to know if it is infact the motor that causes the issue.
    – Matt Clark
    Dec 21, 2015 at 5:22
  • Since the motor runs open loop, simply disconnexting the motor while running software that assumes it is still there should clarify if it is a hardware or software issue. Dec 21, 2015 at 5:55

2 Answers 2


Thanks for the help everyone. I fixed it by using Capacitors. They suppress the noise that the dc motor produces. I found my information here

enter image description here


There are a couple of things that could be causing your problems:

  • The current draw of the motor, especially at start up. The motor may be drawing enough power to pull down the voltage at the processor causing it to crash, or

  • You may be seeing transients as the motor starts and/or stops that are causing the processor to crash.

One way you could detect problems like this is to use the on-board LED as a heart beat or run indicator. You could either blink it in loop() or do something like turn it off just before starting or stopping the motor and then back on afterwards. If the blink stops or if the LED goes out then you know that the processor has stopped running.

As a general rule, except with the tiniest of motors, I'd suggest using the Arduino to control a transistor that controls the motor from its own power supply line (it could be the same supply as the one the feeds the Arduino, just don't run the motor power through the Arduino). That and the suggestions in the comments will go a long way towards isolating the Arduino from the motor and power disturbances it will cause.

  • 1
    Note that the poster is already "using a transistor that controls the motor from its own power supply" Dec 21, 2015 at 16:45
  • Ack, missed that…
    – dlu
    Dec 21, 2015 at 16:46

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