Robotic Boom Arm

Introduction: Robotic Boom Arm

This instructable was created in fulfillment of the project requirement of the Makecourse at the University of South Florida (

The Robotic Boom Arm (RBA) is exactly what it sounds like. A boom arm is an arm or rod used to hold a microphone to someone. The RBA is a boom arm which can detect when a person has moved closer to or away from the RBA and will move the microphone accordingly.


For this project you will need:

  1. PLA
  2. HC-SRO4 Ultrasonic Sensor
  3. Arduino Uno
  4. Bread Board
  5. Jumper Wires
  6. Potentiometer
  7. 3x MG996R 55g Servo Motors
  8. Magic&Shell 5-Pack 25T Round Type Servo Horn Robot Arm Aluminum Alloy
  9. Screw Driver
  10. YwRobot 545043 Power Supply

  11. 9.6W DC power cable

  12. Plastic Weld

This was designed to hold a specific microphone but the the end arm could be redesigned to hold any microphone:

13. Movo VXR10

Step 1: Printing and Assembly 1

Firstly, the physical parts for the arm are made of PLA filament and are to be printed out using a 3D printer using the provided files.

After printing all of the parts the next step will be to adhere all of the servos into place. The first servo will be adhered into the base of the arm. The servo should be oriented so that the wires can come through the hole in the stand that the screws will go into to hold the servo in place; from here the wires can come out out through the hole in the bottom. The Next servo will be placed in the rectangular hole in the base_arm_connection. The servo should be oriented so that the top of the servo is pointed inward toward the center of the circle and the wires are facing up toward the ceiling. The last servo will go into the first arm. The servo should be oriented so that the top of the servo is pointed down into the arm and the wires are coming out facing the closest end of the arm. Once all the servos are in place screw in the servos where the four holes are for each servo in the PLA.

Next we need to adhere the Ultrasonic sensor into the top of the base_arm_connection. Using the plastic weld, apply a coating to the bottom side of the servo and to the base_arm_connection no more than a millimeter away from the rectangular hole on the side that is closest to the edge of the circle. Place the Ultrasonic Sensor so that it faces outward away from the center of the circle. Hold and allow for the plastic weld to dry.

Next we will connect the aluminum disks for the servo connections. There will be three disks used. the first will go on the underside of the base_arm_connection. Place the disk so that all five holes line up and screw the black screws into the four outer holes. Repeat this process on the first arm and the second arm.

Next we will take 4 jumper wires and connect them to the four pins on the ultra sonic sensor/ Run the jumper wires down through the bottom of the base to be attached dot the circuit later.

Step 2: Circuit

In this step we are going to go over the functions of the arm and how to put together the circuit. The way that the are moves is the servos changing their rotational position. The potentiometer controls the servo in the base of the arm. Turing the potentiometer will rotate the arm left and right. The Ultrasonic sensor controls the two servos controlling the arm. The sensor can detect how far away someone is from the arm. There are 5 positions that range from the most recoiled position to the most extended. Moving closer to the arm will recoil the arm, whereas moving further away from the arm will extend it.

To begin place the Arduino in the rectangular base so that the four holes on the Arduino match up with the four spikes in the housing base. Next place the bread board in the space section off by the four corners Place the 545043 power supply into the end of the bread board closest the side opening of the housing base. Now, connect the ground rail of the bread board to the ground pin of the Arduino.

We can now start connecting our sensors. First place the potentiometer the breadboard as close as possible to the 545043 power supply so it straddles the middle of the breadboard. Using the jumper wires, connect the pins of the ground and vcc terminals to the ground and vcc rail. Now connect the final pin of the potentiometer to the A0 pin of the Arduino.

For the Ultrasonic sensor, connect the ground and Vcc pins to the ground and Vcc rails accordingly. Connect the Echo pin to pin eight on the Arduino, and the Trigger pin to pin 9.

Next we will connect the servo wires. Connect the ground and Vcc pins of all three servos to the ground and Vcc rails of the bread board accordingly. For the servo in the base of the arm, connect the final pin to the 3 pin of the arduino, connect the final pin of the servo in the base_arm_connection to pin 10, and the final pin of the servo in the first arm to pin 5.

This will complete setting up the circuit.

Step 3: Code

This is the code that will run the Robotic Boom Arm. The code will create variables for the servo positions and for the pins on the Ultrasonic sensor. Firstly, in the loop the voltage across the potentiometer and change the angle of the first Servo. The Arduino will remember what the last position and will only change if the difference in the analog voltage from the previous reading is greater than 10. Next, the code will read the the distance variable and create memory of the last reading. It will check if the change in distance is greater than 10 and then will change the servos to 5 positions the create the distances of the arms.

Step 4: Final Assembly

Finally put the base of the arm on top of the lid so that the rectangular holes line up and run the wires through both of the holes. Plastic weld the base of the arm to the lid. Next plug in the power supply and the Arduino and run the code. Cover the sensor and turn the potentiometer all the way to the right. Now place the base_arm_connection on the servo on the base. The disk should fit into place on the servo. Now take a black screw and screw it into the center hole of the Base_arm_connection. Do the same with the first arm to the servo on the base_arm_connection so the arm is pointed parallel to the ground away from the ultrasonic sensor. Do this again with the mic_mount arm so that it is pointing straight up. Now place microphone into the mic mount.

Now the assembly is complete remove the cover on the sensor.

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    2 years ago

    Hey there. You mention "provided files" for the 3D printed components in the first step, but I don't see any files attached.