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What is a Servo Motor?

We have built a few projects that have used motors to make things move and along the way we have looked at some of the different types of motors that we can control with our Arduino and Raspberry Pi projects.

We have worked with basic DC motors a few times. We built a couple of robotics projects that are based upon DC motors and we also took an extensive look at the H-Bridge Controller that is commonly used to regulate the speed and direction of a DC motor with a microcontroller or microcomputer.

Another type of motor we’ve worked with is the stepper motor. This type of motor has its shaft driven in discrete steps, allowing for very precise control. They are widely used in printer  and robotics designs.

There is another type of motor that we have used in many of our experiments but have not (yet) taken a detailed look at – the Servo Motor.

Servo Motors with Arduino

A Servo Motor is a low-speed, high-torque motor that comes in a variety of sizes. Unlike the DC and Stepper motors the Servo Motor does not normally spin a full 360 degree rotation. Instead it is limited to a range of 180, 270 or 90 degrees.

A control signal is sent to the servo to position the shaft at the desired angle. This arrangement with a single signal makes it simple fo servos to be used in radio and remote controlled designs, as well as with microcontrollers.

A servo is perfect if you need to position the rudder on a boat or the elevator on an aeroplane.  They are really useful in robotic work to position cameras, sensors or robot appendages.

Servos can also be used as analog gauges like speedometers and tachometers.

Types of Servo Motors

A servo motor is essentially a motor that has an input for a control signal that is used to specify the position of the motor shaft.

Servos are used in industry as well as in hobby applications. Industrial servos are often AC motors with digital control inputs that cost hundreds or thousands of dollars.

We will NOT be working with industrial servo motors today!

Hobbyist servo motors are generally DC motors that can be controlled with either a digital or analog signal.

Digital servos are used in applications that require quick responses like the elevator on an aeroplane or the rudder on a helicopter.  We will NOT be working with these types of motors either, although the hookup and code used to drive them with an Arduino is identical to what we will use for our analog servos.

We will be using plain ordinary analog servo motors, the most popular type for hobbyist use. They are inexpensive and easy to obtain. Mounting hardware is also very easy to find as these servos are of a standard set of sizes.

It should be noted however that while we won’t be working with digital servo motors today they are really very much like their analog counterparts. They use the same PWM control signals as analog servo motors and can be controlled using the same circuitry and code.

Analog Servo Motors

Analog servo motors are inexpensive and available in a variety of sizes and ratings. Perfect when you need a tiny high-torque motor that can be accurately positioned and that won’t break the bank.

The “analog” part of the analog servo motor is the control signal. Analog servo motors respond to a Pulse Width Modulation or PWM signal to position their motor shaft.

PWM is an ideal control medium. It can be generated by a simple timer circuit or with a microcontroller. It can be sent over a single wire or transmitted on a radio or light beam.

The Arduino has a number of PWM capable output pins, making it ideal for controlling servo motors.

How do Servos Work?

A servo motor is a motor with a built-in “servomechanism”.

The servomechanism uses a sensor to monitor the motor shaft position and a controller to control the motor. It is fed a signal that indicates the position that the shaft should be set to. It then moves the motor into the required position.  

In the analog servo motors we will be working with that control signal is a PWM signal whose pulse width determines the angle the motor shaft is to be positioned at.  The motor itself is a simple DC motor with a lot of gearing to slow down its speed and to increase its torque.

In order to function properly the servo motor needs a sensor that can accurately measure its shaft position. On some industrial and high-end hobby servos this is done using an optical interrupter disc, but in most standard hobby servo motors the sensor is a potentiometer.  This works well as these servos typically travel 180 to 270 degrees, well within the range of a potentiometer. However the accuracy of potentiometers, especially in low cost servo motors, can affect the overall accuracy of the servomechanism.

Continuous Rotation Servo Motors

A standard analog servo motor is constricted in its rotation, usually to 180 or 270 degrees (180 is by far the most common). Its internal gearing provides a high torque power pack in a small and inexpensive package.

That combination of small size and large torque also make servos attractive to use as replacements for standard DC motors in the design of small devices like tiny toys and robots. This prompted several people to modify standard analog servos by removing the potentiometer to allow the servo to spin a full 360 degrees.

Manufactures got the message and now offer “continuous rotation servo motors”, essentially servos with the servomechanism disengaged.

In a continuous rotation servo motor the speed and direction of the shaft rotation is controlled by the same PWM signal that is used in a conventional analog servo motor.

Having a simple one-wire controls signal and the same physical package as a standard servo motor make continuous rotation servo motors attractive for a number of applications.

Servo Motor Control Signals

In order to use analog servo motors you need to understand how to control their operation using PWM. The two varieties, conventional and continuous rotation, use the same timing signals but respond to them slightly differently.

Let’s take a look at the PWM signals used in most analog servo motors.

Conventional Servo Motor Timing

In a conventional analog servo motor a PWM signal with a period of 20 ms is used to control the motors. A signal of 20 ms has a frequency of 50 Hz.

The width of the pulse is varied between 1 and 2 ms to control the motor shaft position.

Servo Motor PWM Timing

  • A pulse width of 1.5ms will cause the servo shaft to rest in the 90 degree position, the center of its travel.
  • A pulse width of 1ms will cause the servo shaft to rest at the 0 degree position.
  • A pulse width of 2ms will cause the servo shaft to rest in the 180 degree position.

Varying the pulse width between 1ms and 2ms will move the servo shaft through the full 180 degrees of its travel. You can bring it to rest at any angle you desire by adjusting the pulse width accordingly.

Continuous Rotation Servo Motor Timing

In a continuous rotation servo motor the same PWM signals will cause the motor to perform differently.

Continuous Rotation Servo Motor PWM Timing

  • A pulse width of 1.5ms will cause the servo shaft stop spinning.
  • A pulse width of 1ms will cause the servo shaft to spin at full speed counter-clockwise..
  • A pulse width of 2ms will cause the servo shaft to spin at full speed clockwise.

Varying the pulse width between 1ms and 1.5ms will make the motor spin counterclockwise with the shorter pulse widths causing the motor to spin faster.

Varying the pulse width between 1.5ms and 2ms will cause the motor to rotate clockwise with the longer pulses resulting in a faster speed.

Commercial continuous rotation servo motors will have an adjustment potentiometer that can be used to zero the speed when the motor  is feed a 1.5ms pulse width.

Servo Motor Specifications

There are literally hundreds of analog servo motors available, knowing how to read their specifications is essential to choosing the correct one for your application.

Here are some of the key parameters you’ll encounter when choosing a servo motor.

Motor Size

The physical size of a servo motor is naturally an important consideration, chances are your application will demand that the motor conform to specific size restrictions.

There are a number of standard servo motor sizes, this makes it a lot easier to find mounting brackets and hardware to accommodate your servo motor.

Servo sizes are often specified as follows:

  • Nano
  • Sub-Micro
  • Micro
  • Mini
  • Standard
  • Large

There are also specialty sizes. The Micro and Standard sizes are the ones most often used by Arduino experimenters.

Gear Material

Servos have a number of internal gears plus gearing directly on the output shaft, these serve to slow down the motor speed and increase its torque.

The gears can be manufactured using either plastic or metal.

Metal gears offer better performance, can usually support higher torques and are less subject toi stripping.  Metal gear servos also come at a higher cost.

Plastic gears are more susceptible to stripping and don’t have the torque capabilities of their metal counterparts. They are however quieter and are less expensive than metal geared servo motors.

You can often get the same servo motor with a choice of gears. A common experimenters motor is the SG90, a Micro sized servo motor with plastic gears. Its metal-geared counterpart is the MG90. As they come in the same case and have the same voltage and driver requirements they are interchangeable, with the MG90 offering superior performance because of its metal gears.

Servo motor quality is also affected by the type of bearings and the number of them. Motors with multiple bearings have smoother and more accurate rotation.


The speed of a servo motor is specified as the time required to move the shaft of the servo by 60 degrees.

Servo Motor Specs - Speed

An example rating is 0.25 sec/60°, meaning it takes a quarter of a second to travel 60 degrees.

Servo speed is more applicable to conventional servo motors, continuous rotation motors are rated in maximum RPM like any DC motor.

High speed servos are used in model aeroplane and helicopter application to control elevators and rudders which often need to be moved quickly.  Many of these use digital control and internal optical position sensors instead of potentiometers to allow for more rapid movement.

For hobby applications like controlling the position of a video camera or ultrasonic sensor speed isn’t usually a critical factor.


Torque is a very important parameter, it literally specifies how strong a motor is.

Torque is defined as the amount of force a servo can apply to a lever or in other words how much weight it can hold up.

It is measures in either ounce-inches or kilogram-centimeters. You can convert manually as follows:

  • Multiply kilogram-centimeters by 13.88 to get ounce-inches.
  • Divide ounce inches by 13.88 to get kilogram-centimeters.

Another way is to use an online torque converter.

To understand how the torque figures relate to real world conditions consider the following example:

Servo Motor Specs - Torque

A servo motor is rated at 5 kg-cm.  This would also be the same as 69.4 oz-in (5 x 13.88 = 69.4).

The servo motor can support up to 5kg of load on a lever at a distance of 1 centimeter from shaft center. If you prefer Imperial measurements then it could support a 69.4 ounce load (about 4.3 pounds) at a distance of 1 inch.

At double the distance the load would be halved, so at 2cm from the shaft the lever could support 2.5kg.

Half the distance doubles the load that can be supported to 10kg.

Larger servo motors tend to have larger torque capabilities, motors with greater torque tend to be more expensive.  They also weigh more and consume more current.

Operating Voltage

Most hobby analog servos are rated from 4.8 to 6 volts and achieve their maximum performance at the higher voltage.

There are also more servos being offered with maximum voltage ratings of 7.5 to 8.5 volts. These are becoming more popular due to the availability of 7.4 volt LiPo batteries for model aircraft, boats, vehicles and quadcopters.

Servo motors, especially high torque models, can consume quite a lot of current, this needs to be taken into account when selecting a power supply or battery for your project.

Horns, Arms and Accessories

Most servo motors have a geared shaft that is threaded for a center screw.

In order to make use of the servo you will need to connect the shift to another component in your design – a platform, a gear, a wheel or whatever it is you are trying to move with the servo.

Servo motors come with an assortment of levers and discs of different shapes that can be mated to the shaft to facilitate attaching the servo to your design. These pieces are often referred to as “horns” or “arms”.  They attach to the servo motor shaft and are secured in position with the center screw and they can be made of plastic or metal.

In addition to the horns and arms you should also receive an assortment of mounting hardware and screws with your servo, including the center screw for the shaft (don’t lose it as they tend to differ between servo types).

You can also buy mounting plates designed to accept popular servo sizes like Micro and Standard.

The availability and interchangeability of servo horns, arms, mounting hardware and accessories makes it easy to incorporate servo motors into your designs.

Testing Servo Motors

As with any component its useful to know how to test a servo motor to ensure proper operation.

This can be very helpful when you are about to mount the servo into a mission-critical application, or just into something that would be a pain to have to take apart if the servo turns out to be faulty!

It is also useful to be able to rotate the servo shaft into a preset position (for example 90 degrees) before mounting the sero into your project so that everything gets aligned correctly.

There are a number of methods you can use to test a servo. A simple Arduino sketch and connection like the ones you’ll be seeing here further on will make an excellent method of testing a servo and of positioning its shaft into a preset position.

Another way of doing this is by using a dedicated servo tester.

Servo Testers

As you might imagine a Servo Tester is a device used to test servo motors!  They are very useful and can be very inexpensive, depending upon the features you want.

A simple servo tester like the one shown here (and used in the accompanying video) can be had for just a couple of dollars.

More advance servo testers have speed and centering controls for multiple motors, some also have current meters. Even these are under 20 dollars.

These units need to be powered by the same power supply (or equivalent) that you’ll be using the power the motors themselves. They can be plugged in to a standard servo motor connector and they will take control of the servo.

The servo testers will allow you to manually move the motor and to center it at the 90 degree position. This lets you check the motor for correct operation and to align its shaft position before you fasten horns or arms to it.

Servo Motor Connections

Analog servo motors typically have a 3-pin connector. On some more expensive motors the motor cable can be removed at the motor base and replaced if required, other motors have the connector permanently wired onto a short 3-wire cable.

The color codes used on hobbyist servo motors varies depending upon manufacturer. However most manufacturers observe the same pinout, as shown in the following diagram:

Servo Motor Pinout

The three connections to the servo motors are as follows:

  1. Ground – The common ground for both the motor and logic.
  2. Power – The positive voltage that powers the servo.
  3. Control – The input for the PWM control signal.

The most common connector is the standard DuPont variety with 0.1 inch spacing. This makes it easy to connect servo motors to your project using standard DuPont header strips.

You can also insert breadboard wires directly into the servos 3-pin connector so you can prototype with servo motors.

Connecting to an Arduino

As we have already described a servo motor requires a PWM control signal to operate correctly.  You can generate this signal many ways – a simple timer circuit, a dedicated control chip or using a microcontroller with PWM output capabilities.

The microcontroller naturally has many advantages in being able to control the servo more effectively. And an Arduino is an excellent choice.

The Arduino IDE has a Servo library already included so adding a servo to your sketch is very simple as you will soon see.

PWM Output

All Arduino boards have some output pins that are capable of Pulse Width Modulation or PWM. On an Arduino Uno there are 6 PWM-capable pins.

Keep in mind that to generate the PWM signals the Servo Library will need to use some of the internal Arduino timers, specifically Timer 1.  This can interfere with other libraries that also need the same timers. One way around this is to look for alternate libraries for either the servo of=or the other desired function, this is a common way of getting around these restrictions.

A more advanced method is to use an external PWM controller board and free up the Arduino timers. This will be discussed further in this article.

Power Supply Considerations

Most servo motors will happily operate on 5 volts, making it tempting to use the 5-volt output on the Arduino board to power the servo.

It’s not really a very good idea.

Servos can consume a fair amount of current, especially when placed under load. This might be more current than the voltage regulator on the Arduino board can take, especially on cheaper clone boards.  While most Arduino boards can support one Micro servo it still taxes the regulator a lot.

Servo motors, like all other motors, can induce electrical noise onto the power supply lines. Having that noise on the lines powering your microcontroller and other logic devices can often lead to system errors.

It is a much better idea to use a separate power supply for your servo motor. A 5-volt USB 3  power supply would work well, as would a 6-volt lantern battery or 4 type AA or C batteries.

If you REALLY must power a servo directly from the Arduino limit it to one micro servo. A capacitor of 100uf or greater across the power supply line near the servo can help absorb those power surges.

The Sweep Sketch

For our first Arduino sketch we will use one of the built-in examples that is packaged with your Arduino IDE. No code to write or libraries to install!

Wiring up the hardware to use with our first demonstration is very simple. You’ll need an Arduino (any type), a servo motor and a power supply for the servo motor.

Arduino Sweep Sketch Servo Hookup

The hookup couldn’t be simpler. The servo is powered by its own power supply and the ground connection is also connected to the Arduino ground. Then the control lead from the servo is connected to pin 9 on the Arduino.

Pin 9 on the Arduino Uno is one of the six pins that are capable of PWM, on most Uno boards you’ll see a symbol beside the 6 PWM-enabled I/O pins.

Hook your Arduino up to your computer and start the Arduino IDE.

Click the File menu at the top of the screen.From there select the Examples sub-menu.

A list of example sketches will be displayed. It is divided into sections, scroll down the list until you get to the “Examples from Libraries” section.

In the “Examples from Libraries” section you will see “Servo”.  Highlight that to reveal two sketches, Knob and Sweep.

Load the Sweep sketch.

Sweep is a very basic sketch that just sweeps the servo shaft from one extreme to the other.

The sketch makes use of the Arduino Servo Library which is included with your Arduino IDE. As its name implies its is a library for controlling servo motors with PWM.  We include the library and define an object called myservo to represent our servo motor. If you have multiple servo motors you can define an object for each of them.

We then define a variable called “pos” that holds the position (angle) that we want the servo motor shaft to move to.

In the setup we attach our servo object to the servo motor control line on pin 9 of the Arduino.

Then the loop, which consists of two for loops.  The first loop increments the value of the pos variable and uses it to control the servo motor using a myservo.write command, sending the shaft from 0 to 180 degrees.

The second for loop is identical except it decrements the value from 180 to 0, sending the shaft back in the opposite direction.

Load the sketch into the Arduino and observe the servo motor shaft, it should be travelling from one end to the other.

You just made a servo move with an Arduino!

The Knob Sketch

Let’s move on to the other demo sketch included with the Arduino IDE, the Knob sketch. Before we do we’ll need to add a component to our circuit.

Arduino Knob Sketch - Hookup

As the wiring diagram shows you’ll need a potentiometer, any value from 10k up will work fine. Hook one end of the pot to ground, the other end to the Arduino +5 volts. The wiper is connected to analog input A0.

The potentiometer will serve as a control to position the shaft of the servo motor, you can use it to dial any position on its 180 degree travel.  Not only is it a good demonstration it also can be a useful function for setting the position of servo motors before mounting them into your project.

If you substitute a continuous rotation servo in the circuit you can use the potentiometer to control both the speed and direction of the motor’s rotation.

After you modify the experiment to include the potentiometer open the Arduino IDE and go back to the example sketches. This time select Sweep from the Servo menu.

The Sweep sketch is also very simple. Like the Knob sketch it uses the Arduino Servo Library which it includes and then creates a myservo object to represent the servo motor.

We then define a couple of integers. The first one, potpin, represents the analog pin we used for the potentiometer wiper connection.  The other one, val, is the value taken when reading that analog input.

The setup is identical to the Knob sketch, we attach the servo object to pin 9.

In the loop we start by reading the value from the analog pin, a value of 0 to 1023 which will be assigned to val. Next we use the Arduino Map Function to change val to represent the angle between 0 and 180 degrees.

After that we use a write command to position the servo to the value of val, the angle selected by the potentiometer.

After a brief delay to allow the servo motor to catch up we do it all over again.

Load the sketch up to your Arduino and turn the potentiometer. You should see the shaft of the servo motor move in time with the pot.

Once again the sketch illustrates just how easy it is to control a servo with your Arduino.

PCA9685 Servo Driver Board

Controlling servo motors from an Arduino directly is pretty simple as we just saw. However it has its limitations:

  • You are limited by the number of PWM pins on your Arduino. If the servo is part of a design that requires other PWM devices that may be a problem.
  • The Arduino Servo Library can conflict with other Arduino libraries as they attempt to use the same timer. This can sometimes be solved by looking for alternative libraries.
  • You need to control a LOT of servo motors, even an Arduino Mega has its limitations here.

A better solution all around is to use a separate servo driver board. This will offload the task of sending PWM to the servos, freeing up your Arduino to do better things.

The board we will be using is based around the PCA9685 chip. These boards are extremely popular and are manufactured by several companies.

The PCA9685 board uses I2C to communicate with the Arduino. This means only two connections for clock and data are made to the Arduino. As the boards I2C address can be configured using a series of solder pads you can use many of them on the same circuit.

Each board can control up to 16 servo motors. And you can cascade up to 62 boards to control a whopping 992 servo motors!

If you honestly need to control over 992 servo motors you could use an I2C shield to connect multiple I2C buses to your Arduino!

The connections to the board are very simple.

PCA9685 Pinout Diagram

There are a set of identical connections on each side of the circuit board, this makes it easy to connect several modules up in a row.  They are as follows:

  • GND – The Ground connection.
  • OE – Output enable. You can use this pin to enable and disable all of the 16 outputs. Typically it is left unconnected which will result in all outputs being enabled.
  • SCL – The Clock line for the I2C bus.
  • SDA – The Data line for the I2C bus.
  • VCC – The logic power supply, +5 Volts.
  • V+ – the power for the servo motors. There is also another connector on top of the board for this and that connector is preferable as it is reverse polarity protected while V+ is not. The V+ pins are really used to cascade multiple PCA9685 modules and power all the servos off of a single power supply.

There is also a 2-pin screw connector at the top for the servo power supply. As mentioned above it is reverse polarity protected.

On the bottom of the board are 16 sets of 3-pin male connectors. Each one is used for a servo motor.

On the top right of the board are six solder pads. These are used to setup the I2C address for the board. If you are using more than one board you’ll need to jumper one or more of these to change its internal I2C address to be unique.

The base address for a PCA9685 module with none of the jumpers shorted is 0x40.

If you short out the A0 solder pad the address becomes 0x41.

Bridge A1 instead and it’s now an address of 0x42. Bridge both A0 and A1 and the address will be 0x43.

Multiple Servos – Controlling the MeArm

In order to demonstrate the use of the PCA9685 PWM module to control multiple servo motors I decided to bring out the MeArm which I built earlier. It has four servo motors.

I connected everything up as follows:

PCA9685 Arduino Hookup

You’ll notice that I also added four potentiometers, as before these can be any value of 10k or above and will be used to regulate the operation of each of the four servo motors.

The PCA9685 module hooks up to the SCL and SDA connections on the Arduino. If your Arduino does not have pins for these I2C connections then use analog pin A4 for SDA and pin A5 for SCL.

Note that even if you do have separate SCL and SDA pins you won’t be able to use A4 and A5 as analog inputs when using I2C.

The four potentiometers connect to ground on one side and 5 volts on the other. Their wipers connect to analog inputs A0 through A3.  

The Arduino power is also used to power the VCC power on the PCA9685 module.  A seperate power supply for the four servos is connected to the screw connector on the module.

I connected my servo motors to outputs 0, 4, 8 and 12. You can actually use any four connections, just note them so you can modify the code to match your selection.

As this is the only PCA9685 module I’ve connected to the Arduino I didn’t short out any of the address solder pads.

Now let’s look at the sketch I’m using to make this all work:

The sketch makes use of the Adafruit PWM Servo Driver Library which you will need to install to make this work.  It can be installed from the Library Manager in your Arduino IDE.

  • Open the Arduino IDE.
  • Select Sketch from the menu at top.
  • Select Include Library. A sub-menu will appear.
  • Select Manage Libraries… from the sub-menu.
  • The Library Manager will open.
  • Search the Library Manager for “Adafruit PWM”
  • The Adafruit PWM Servo Library Driver should be the first result.
  • Click the More Info link to reveal an Install button. Use this button to install the library into your IDE.
  • Close the library manager.
  • The library is now installed and can be used in your IDE.

We begin the sketch by including the Wire library. This is built into your Arduino IDE and is used to control I2C communications.

Next we include the Adafruit PWM Servo Library that we just installed.

We will now define a few constants.  

The first two constants define the minimum and maximum pulse width for the PWM signal we will be sending to our servos. A you recall this pulse width will determine the position of the servo shaft.

The third constant we define is the PWM frequency, which for analog servo motors is 50 Hz.  If you are using digital servo motors you may want to increase this as they can often use frequencies as high as 200 Hz.

Next we create an object called pwm using the Adafruit PWM Library. If you used an address other than the default 0x40 you would need to define it here.

Now we define some variables. The first one is the potentiometer input pins, A0 through A3. After that are the motor outputs on the PCA9685 board, I used 0, 4, 8 and 12 when I hooked up my motors. Change these values if you used different connectors for your motors.

Now onto the Setup. We initialize the pwm object we created earlier and then set the frequency of the PWM oscillator to the frequency we defined, which in our case is 50 Hz.

Now we create a function that will drive the motors in response to the potentiometer positions.  We can then just call this function for each motor.

Our function is called moveMotor. It has two inputs, controlIn which represents the potentiometer input and motorOut which represents the motor connection on the PCA9685.

The function reads the potentiometer value and converts it to a pulse width. This pulse width is then used with the setPWM method of the Adafruit PWM Servo Library to send the pulse to the motor specified by the motorOut variable.

In the loop we just call the moveMotor function four times, once for each potentiometer-servo motor combination.

The result is that the four servo motors in the MeArm will respond to the potentiometers. In the demo I used slide potentiometers which made it a lot easier to precisely position the MeArm (I use the term “precisely” with a lot of poetic license!).


Servo motors are versatile little devices that have a myriad of uses in hobbyist projects and knowing how to control them is an essential Arduino coding and wiring skill.

Hopefully this article and its associated video have helped shed some light on using servo motors, either connected directly to an Arduino or via I2C using a PCA9685 PWM controller.

So grab yourself a bunch of servo motors and start making things move today!


Parts List

Here are some components that you might need to complete the experiments in this article. Please note that some of these links may be affiliate links, and the DroneBot Workshop may receive a commission on your purchases. This does not increase the cost to you and is a method of supporting this ad-free website.





Code for this article – The sketches used in the article in one easy to use ZIP file.

Adafruit PWM Servo Library – The Adafruit Library for controlling the PCA9685 16-Channel controller board.

Arduino Servo Library – The Servo library included with the Arduino IDE.


Using Servo Motors with the Arduino
Using Servo Motors with the Arduino
Article Name
Using Servo Motors with the Arduino
Learn how to use analog servo motors with the Arduino. Covers the Arduino Servo Library and using the PCA9685 PWM controller to control multiple servo motors.
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DroneBot Workshop
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İsa düzgün
5 years ago

I’m working on a project. I have a problem. I need to use a dc motor and servo motor in the project. However, dc motors do not move when I include the servo motor in the software.

jordan sipsip
5 years ago
Reply to  İsa düzgün

I have the same query. I hope it will be answered soon.

jordan sipsip
5 years ago

Can I reliably use 3 DC motors and 1 servo with my UNO board? The 12 DC motors will be used to feed and throw balls for my DIY pingpong Robot and the micro servo will be for left and right movement of the robot’s “head”. I’ll power the Uno with an outboard 5v supply from which the servo will also get its power.
Thank you for your effort building this site. Most informative and easiest to understand arduino site yet.

5 years ago

Hi, I am thinking of using servos to control window shutters by remote using mega 2560 and wifi has anyone done this? I think it would be great to get Alexa to do the task.


5 years ago

Hi DB Team, firstly sorry for very basic question. I am building servo based robotic arm (just to learn). However I don’t understand how to pick sufficient power supply. Servo that I am using is MG966R (4.7V-7.2V, 500mA – 900mA). Thing that I can’t understand is “what power supply should I connect to PCA9685 to ensure that each servo has enough power under maximum load of ~10kg)?” Should I add all the current consumption and look for 5V, 3A power supply or 5V, 1A will be enough?

Bob Young
5 years ago

I am curious as to the maintenance and improvement of the mechanical operation of servos with regard to ‘been there, done that’ experiences. I ask as I have several new servos (HD-3001HB, all of which demonstrate current spikes and mechanical jitter during slow servo movement. I am curious if this problem can be resolved by cleaning/lubrication of the mechanics on the servo.

Scott Morgan
5 years ago

Dear Sir, I need to have a servo move a string in my project on a crane I am building for a model RR. You mention speed of motion in your article, however you did not comment on how to change the speed to slow the arm motion down as needed for my application. Can you make a comment on this? Perhaps it’s done in the code, but I do not know how to do this. Thank you for your efforts in all your excellent videos. Tyro Novice…

5 years ago

I am using a servo to control a robot arm and when I remove power and turn on the servo jumps. THe robot arm cannot handle the sudden movement.What code can I use so the servo begins and ends at the same place?

John Marshall
5 years ago

Hi, I have been looking for similar circuit and servo for modelrailway points control and signal control and I think if I replace the Pot with a switch in the 4 pot circuit I can swing from Max to Min and adjust the pulse width to get the correct angle I require and maybe play around with the sketch once I get it working and adding more servo’s would probably have to use an Arduino Mega. but all in all a great design..

Regards john

Eduardo Pinheiro
5 years ago

Hi, How can I change the code to use 4 datas received from Serial to control the servos. Insted of reading potentiometes, how can I read 4 variables and send to the servo? Thanks a lot. Your tutorial is great.

5 years ago

Ola, preciso jampear algum pino I2C?, meu servo não tem controle com a placa PCA9685.
uso o mega 2560.pode dar uma ajuda, preciso fazer um braço robotico de seis eixo. meu servo e de 360º continuo

4 years ago

thanks for the instruction video

4 years ago

I am using PCA9685 and working perfectly with sample sketch.How to assign pins SCL and SDA other than default A5 and A4 from arduino promini? Let say assign it to pin A7 and A8. Thank you.

Justin Long
4 years ago

Concerning this particular board and researching the data sheets, I can NOT find a definitive answer to this question; Is it possible to control different types of servos that require a different PWM on this board OR are multiple boards needed?? IF possible, how would one go about “addressing and configuring” said motors?? I’m building a Bot consisting of a 6DOF Arm mounted on a tracked chassis. The Chassis will have 2 brushless motors with board to power. The 6DOF has 4 “Standard” size servos and 2 “Mini” for wrist rotate and Grip. The servos require different PWM. A good… Read more »

4 years ago

Hi, I have three SG90 micro servo, which is attached to an arduino mega2560. I noticed it there is a little unexpected movements of the motors every time when I power up or reset the board. Could you know what is the reason? Initialization or noise on the sginal wire?

4 years ago

Sir I want to know if it is possible to control 6 servo motors by PCA9685 16-Channel controller board wirelessly by bluetooth modules or nrf24l01 modules

Ezirim uchechukwu
4 years ago

Please,l am happy to be in this group.Please Hw can l control a robotic arm automatically to do a repeated task without using a potentiometer.

Pedro Vazquez
4 years ago

Sir, you are one of the bests in Aeduino!!!!

4 years ago

Please,l am happy to be in this group. Please Hw can l control a robotic arm automatically to do a repetitive task without using a potentiometer.

Sea Glass
4 years ago

I watched your tutorial on photometers,arduinos, and servos. I trying to build a unit to operate slide pots. to run servos to shift a transmission from neutral to forward, neutral, and reverse. the other unit to run throttle. one question, i seen your arduino was powered by a 9V battery, does the arduino need 9v to operate? it powered up when i hooked power to the output circuit, would that work, using 5 volts?

Harry Tyler
4 years ago

Thank you for this excellent article. It has helped me to identify the faulty servo in a set of 12

3 years ago

i powered my servo with eternal 6v and my servo suddenly spun and then got stuck can i get a solution for this

3 years ago

The Dronebot workshop tutorials and videos are very simple to understand and follow. They have helped me to understand – controlling DC motors, stepper and servo motors. I am very grateful to you

Gary M. Oosta
3 years ago

As always, the presentation is clear and concise and it works! I learned something today. Thanks.

ronald a buchwald
3 years ago


Hassan Ali
3 years ago

Am I able to use this sketch with a little modification to control multiple servo motors without the potentiometers. i.e. directly from the code?

3 years ago

Thank you for all of your servo motor, robot arm and motor controller videos and articles. I have recently begun learning about servos, how to power them and how to code for them. Your work has been very helpful. I have watched this video on youtube several times as a reference and continue to do so. Keep up the great work. Don’t change a thing. Your channel is great!

Chris Brown
3 years ago

I’m trying to design a lightweight pan and tilt for the end of a 5mtr crane. (Obviously, got to keep weight down to keep the counterbalance weights small. Which is why I’m using 20mm x 10mm rectangular box aluminium arms in an accordian / scissor design) I investigated steppers, but they can only run at low speeds, (one I have does 1rpm per 4 sec!) and are bulky. DC motors? Run at constant speed, and difficult to speed control via PWM since at lower speeds they need inertia before they will turn. Brushless motors? At about 20,000+ spin speed, and… Read more »

3 years ago

I am making a 2″ access hatch ‘open and close’….But it uses Gears, so I can’t use
default Servo mode. Model Servocity 2000 Series Dual Mode Servo (25-2)I suppose I could use the ‘continuous’ mode sweep sketch, but add some time delay loop to
attain ‘Full open’- ‘Full Closed’ ? Guess back up with limit switches so as not to ruin the servo motor? Read the ‘switches’ while Loop is timing out.
…IF switch=ON before Loop ends, then make Loop condition as timed out? Just pondering.

Richard Funnell
3 years ago

Hi Did you ever finish the DF robot using the MPU6050?

3 years ago

only issue that I can see arising from the setup you propose is that of timing, you might want to use an Arduino Mega 2560 inste

Allan Hockley
3 years ago

i love your Chanel. keep up the good work Bloke… from all of us in Australia, your a bloody good bloke!!!!

3 years ago
Reply to  Allan Hockley

Yes it’s true

Miljenko Sinjeri
3 years ago

Michael Kristensen
3 years ago

Is there a type of Servo Motor that does not offer counter-resistance when manipulated manually? I.E. I want a Motor that can open a small gate by itself, but does not become a brake for the gate when not being used. So I can open the gate by hand, but also by remote.

3 years ago

Hi there I bought 2 HSR-2645CRH continuous rotation servos and I need to connect them to Arduino using PCA9685, I looked over the internet and I could not find
Anyone can help me to know how to set these values?

Peter Bolke
2 years ago

Hi Bill, I read your bio and was relieved that read that you have had such a life-long passion for electronics…you obviously find all the concepts so easy! I am guessing I am a similar age, but have no previous electronics experience, so I am near the bottom of a very steep learning curve I think… Thank you for your very clear way of explaining the components that you use and the diagrams and coding that is so helpful too. My Question: Your 4 x servo motor example where you used the PCA9685 power module was very interesting. My project… Read more »

2 years ago

Hello sir, thank you for the teachings in your channel!

I tried the code you use here, but it doesn’t work. My servo’s don’t move.
All the wiring is correct. I use 10k potentiometers and SG90 servo’s.

I notice that in your code the “pwm” is orange and in my code it stays black.
The used Adafruit-PWM library is version 2.4.0

Could it be that something was changed in a newer version of the library?
Does anyone knows a way to solve this?

Broderick Dell
2 years ago

Im doing a project that requires me to code a micro servo in a full circle at very high speed. I have searched the entire internet and cant find the code for a MG90s servo to go in a full circle in arduino. Could someone help me with this?

2 years ago

Hello Price ?? Model Railway fan older person. No time now to start learning software from scratch Wish: Package: Arduino/16 channel addition board with software (as you describe) Package ready to go. Manual switch input for each servo. Just highlight the bits in s/ware I need to change to set up the angles for each servo and which one goes first Just like this Need latching inputs for each servo not momentary Bonus to have infra red or other capability for wireless remote operation as well as discrete switch operation Price ? Lots of us. good market Advanced in… Read more »

benson tudi
2 years ago

group join

Alberto Pinero
1 year ago

I fly remote control aircraft, I have been learning a lot with your videos, thank you so much for what you do.
I’m working on a pilot that can move his head and arms before take off. I still have a lot to learn but once I finish should looks great.

Again appreciate what you do with your videos and the easy way to understand the connection and sketch in the way you do it.

1 year ago

Hi copied you servo rated programeme using potentiometers
I need to use buttons or toggle switches to operate my servo motors on a single movement I am usung SG90 tower pro and have the PCA9685module, with an arduino uno. apptreciate pointing me in the right direction. thanks JP.

1 year ago

How to controle continuous rotation sevo motors using pca9685

1 year ago

A control signal is sent to the servo to position the shaft at the desired angle. This arrangement with a single signal makes it simple fo servos to be used in radio and remote controlled designs, as well as with microcontrollers.

7 months ago

can you explain how to control the 5 DOF robotic arm through bluetooth

4 months ago

There are several video’s out there of people with blind projects, you just have to look. Remember there are several different types of blinds and each may require special consideration on which type of motor to use. I used a stepper as it has a good deal of torque and very controlable with a 12v dc power supply. You will need a 3D printer to design and make the parts for your project.

Henry E
3 months ago

I love this project but how can it be incorporated on a car so that it can move from one place to other. Pls, how do I get the part for this project supplied to me in Nigeria, Africa