Here is the wiring The image is as clear as I can make it.

Here are the basics of my problem. My program is meant to make 6 red LED lights in sequence fade in and out, toggle 5 white LED's on and off with a button, and make a servo rotate from 90 to 15 degrees on a button press, and revert to 0 degrees when the button is no longer pressed.

All of my code has compiled correctly, the LED's do what they are supposed to do, but the servo is acting strange. At first, it would move fine but then after a few button presses it would kind of spaz out and glitch back to place instead of smoothly move, which will not work for my purposes. After even more time, the servo stopped working at all. I looked around and found some answers saying to route it through an alternative power source, but I did that with the power module that came with my kit and it still refuses to move. I swapped it out with a different servo and that one won't work either, which makes me wonder if my wiring is incorrect - and yet the motor is on and makes vibrations, instead of moving, so I know power is getting through. In addition, the onboard LED's on the mega2560 are turning on and off in response to my button, so I know that's wired in correctly as well! So why won't the servo move, and why won't it respond to my button presses?

Basically, using a 3.3V - 5.0 volt Elegoo power module, how do I correctly wire the servo to only draw power from the 9v battery I attach to said module? I've seen people saying something about putting the grounds of the board and the module together but I don't know how to do that and I'm getting frustrated looking all over the internet trying to find out how so I figured I would just ask a question.

Wiring details:

The 5 white LED's are in parallel, and the red LED's are in series; they are all powered by the arduino's 5V power source, and wired into the arduino GND pin. Servo is connected by to pin 10, and the ground and power are both routed through the 5V power module which is attached to a 9V battery. The light on the module is on, and I have used the included jumpers to make sure I'm using the 5V source and not the 3.3V one.

Here is my code:

#include <Servo.h>
Servo servo1;
// White LED's:
int wL1 = 3;
int wL2 = 4;
int wL3 = 5;
int wL4 = 6;
int wL5 = 7;
// Red LED's:
int rL1 = 8;
// Buttons:
int wLbutton = 2;
int wLreading;
int wL1state = HIGH;
int wL2state = HIGH;
int wL3state = HIGH;
int wL4state = HIGH;
int wL5state = HIGH;
int wLprevious = LOW;

int servoButton = 1;
int servoState = false;
int servoReading;
int servoPrevious = LOW;
// Fading:
int brightness = 0;
int fade = 1;
// Delays:
long time = 0;
long time2 = 0;
long debounce = 100;

unsigned long previousMillis = 0;
const long interval = 1000;

// Setup ======================================================================================================================================

void setup() 
  pinMode(wL1,OUTPUT);          // White LED's

  pinMode(rL1,OUTPUT);          // Red LED's

  pinMode(wLbutton, INPUT);     // Buttons
  pinMode(servoButton, INPUT);  

  servo1.write(90);             // Servo

  if (wL1state = HIGH)
  wL1state = LOW;                                                              // Set the state of the all White LED buttons to low at the beginning of the circuit (this doesnt run after the first time).
  wL2state = LOW;
  wL3state = LOW;
  wL4state = LOW;
  wL5state = LOW;

// Loop =========================================================================================================================================

void loop() {

// White LED Button -----------------------------------------------------------------------------------------------------------------------------

wLreading = digitalRead(wLbutton);                                             // Read the state of the White LED Button

if (wLreading == HIGH && wLprevious == LOW && millis() - time > debounce)      // If the button is different state from last reading and ignores noise
  if (wL1state == HIGH)                                                        // If the current button state of the White LED button is high
  wL1state = LOW;                                                              // Set the state of the all White LED buttons to low
  wL2state = LOW;
  wL3state = LOW;
  wL4state = LOW;
  wL5state = LOW;
  else {
    wL1state = HIGH;                                                           // Otherwise, set the state of the White LED button to high
  time = millis();                                                             // Set the last time the button was pressed to the current time


wLprevious = wLreading;                                                        // Set the previous reading of the White LED button to current reading

// Servo Button ----------------------------------------------------------------------------------------------------------------------------------

servoState = digitalRead(servoButton);

if (servoState == HIGH) 

// Red LED'S breathing ----------------------------------------------------------------------------------------------------------------------------

 analogWrite(rL1,brightness);                                                 // Write the set brightness to the red LED
 brightness = brightness + fade;                                              // Set new brightness to brightness value + fade value

 if (brightness <= 0 || brightness >=255)                                     // If brightness is less than 0 or more than 255
  fade = -fade;                                                               // Negate the fade value, reversing the direction of the fade
  delay(10);                                                                  // Wait a short delay to see the fade

  • 2
    When you say 9V battery, do you mean one of those rectangle shaped alkaline ones with two terminals on top? Those aren't really good for powering motors or servos. They can't really produce much current. They're the equivalent of 6AAAA batteries. I don't know if this is all of your problem but you should use some AA or AAA and you will have a better time of it.
    – Delta_G
    Apr 23, 2020 at 1:34
  • Show us your circuit. That should seem obvious since you said that you thought the fault may be in the wiring. Do you have a pull-down resistor for the buttons? Why don't you have them wired the normal way to read LOW when pressed so you can use the internal pull-ups and don't have to have extra resistors?
    – Delta_G
    Apr 23, 2020 at 1:38
  • is the servo problem repeatable? ... does the servo work correctly after a reset and then degrades after a few button presses?
    – jsotola
    Apr 23, 2020 at 1:50
  • @Delta_G Thank you for the info on the 9V battery, yes that's the kind I am using. I'll have to buy a AA or AAA battery pack. How many of those do I need to power the servo then? As for your second comment, the reasoning behind my white LED's having multiple resistors is that in the future I want them to turn on in sequence with a short time period between each consecutive light, rather than all at once, but I just haven't figured out how to do that yet. I'll leave that to a separate question. I'll attach a photo to my post if that helps. Apr 23, 2020 at 12:26
  • @jsotola no, it won't work at all currently, even after a reset. Apr 23, 2020 at 12:28

1 Answer 1


I've seen people saying something about putting the grounds of the board and the module together

Yes, I believe this is what you need to do.

Servo is connected by to pin 10, and the ground and power are both routed through the 5V power module which is attached to a 9V battery.

From what I understand, you are wiring like this

Servo 5V - 5V Power module

Servo GND - GND Power module

Servo Signal - pin 10 Arduino

If so, you need to make a Y-connection like this:

Servo GND - Power module GND - Arduino GND (these 3 pins should be connected together)

  • I've connected the three together and still nothing. I have noticed that as soon as i connect the servo to the power module, the green light turns off. Is this a result of the power of the 9V not being enough? Apr 23, 2020 at 12:33
  • You can see in the photo I attached in the post on the left, the Y connection you mentioned. Apr 23, 2020 at 12:46
  • Hmm before anything I see a weird thing in your image. In your Y connection you are connecting the yellow wire from servo. Are you sure it's the GND wire?
    – duk3
    Apr 23, 2020 at 14:49
  • And I also recommend you do this way. First, remove all LEDS and try to make your servo work. Then, you can add LEDs. That way you can easily figure out where the problem is. Just divide into steps, don't try to combine everything at start.
    – duk3
    Apr 23, 2020 at 14:59
  • That was the issue. It worked and began responding again one I fixed the y connection. Then I got my 9v dc plug and using that the servo began working. Thank you so much. Apr 23, 2020 at 16:18

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