Arduino Uno - Controlling a DC Motor

Embedded

Electronics

Published

November 12, 2019

Modified

November 23, 2019

Even small DC motors can draw more current than the 40mA maximum provided by an Arduino UNO on a single GPIO pin. By using a Darlington Transistor it is possible to control a separate 9V battery power source for the motor able to provide much higher current.

The base activation voltage for a Darlington Transistor pair is the sum of 2 x 0.7V = 1.4V. With a 2kΩ resistor at the base of the transistor the current drawn from the connected Arduino used to control the motor will be limited to approximate 1.8mA.

(5V-1.4V)/2000Ω = 1.8mA

The TIP120 NPN (121/122) are rated for voltages of at least 60V and a current up to 5A. This Darlington transistor pair acts like one transistor with a current gain of the product of both individual transistors. The data sheet states a current gain up to 1000. This is more than sufficient to drive a small DC motor.

Components

List of required components:

Pcs.	Name	Description
1	UNO	Arduino UNO, digital pins D#2 and D#9
1	M1	DC motor Johnson NF143G-10428
1	TIP	TIP120 Darlington Transistor #1 base, #2 collector, #3 emitter
1	D1	1N4001 Diode collector #1 (-) and anode #2 (+)
1	R1	Resistor 10kΩ
1	R2	Resistor 2kΩ
1	B1	COM-00097 push button (single pole, single throw)

Setup

List of connections:

Button B1 terminal #1 to 5V
Button B1 terminal #2 to the R1 resistor terminal #1
Button B1 terminal #2 to pin D#2 on the Arduino UNO
Resistor R1 terminal #2 to ground GND
Transistor TIP base terminal #1 to R2 resistor terminal #2
Resistor R2 terminal #2 to pin D#9 on the Arduino UNO
Transistor TIP collector terminal #2 to diode D1 collector (negative) terminal #1
Transistor TIP emitter terminal #3 to ground GND
Diode D1 anode (positive) terminal #2 to 9V
Motor M1 terminal #1 to diode D1 anode #2
Motor M1 terminal #2 to diode D1 collector #1

Connect the 9V battery (+/-) to the bottom breadboard power supply line, and connect 5V and GND pins from the Arduino UNO to the top breadboard power supply line. Connect ground of both breadboard supply lines.

Code



#define BUTTON 2
#define MOTOR 9

void setup() {
  pinMode(BUTTON,INPUT);
  pinMode(MOTOR,OUTPUT);
}

void loop() {
  if(digitalRead(BUTTON) == HIGH) {
    analogWrite(MOTOR,255);
    delay(200);
  }
  delay(1);
}

Measurement

	Voltage Drop
R2 resistor	3.02V
TIP collector-base	1.34V
TIP collector-emitter	0.64V
M1 motor	7.81V

	Current
TIP base	1.5mA
TIP collector	15.02mA

If the motor shaft is blocked (can not continue to rotate) the stall current peaks at 105.5mA at the TIP collector.

--- title: Arduino Uno - Controlling a DC Motor categories: - Embedded - Electronics date: 2019/11/12 date-modified: 2019/11/23 --- Even small DC motors can draw more current than the 40mA maximum provided by an Arduino UNO on a single GPIO pin. By using a Darlington Transistor it is possible to control a separate 9V battery power source for the motor able to provide much higher current. The **base activation voltage** for a Darlington Transistor pair is the sum of 2 x 0.7V = **1.4V**. With a 2kΩ resistor at the base of the transistor the current drawn from the connected Arduino used to control the motor will be limited to approximate **1.8mA**. (5V-1.4V)/2000Ω = 1.8mA The TIP120 NPN (121/122) are rated for voltages of at least 60V and a current up to 5A. This Darlington transistor pair acts like one transistor with a current gain of the product of both individual transistors. The data sheet states a **current gain** up to 1000. This is more than sufficient to drive a small DC motor. #### Components ![Required Components](arduino_dc_motor/components.jpg) List of required components: | Pcs. | Name | Description | |------|---------|----------------------------------------------------| | 1 | **UNO** | Arduino UNO, digital pins **D#2** and **D#9** | | 1 | **M1** | DC motor Johnson NF143G-10428 | | 1 | **TIP** | TIP120 Darlington Transistor **#1** base, **#2** collector, **#3** emitter | | 1 | **D1** | 1N4001 Diode collector **#1** (-) and anode **#2** (+) | | 1 | **R1** | Resistor 10kΩ | | 1 | **R2** | Resistor 2kΩ | | 1 | **B1** | COM-00097 push button (single pole, single throw) | #### Setup ![Circuit Schematics](arduino_dc_motor/schematic.png) List of connections: * Button **B1** terminal **#1** to **5V** * Button **B1** terminal **#2** to the **R1** resistor terminal **#1** * Button **B1** terminal **#2** to pin **D#2** on the Arduino **UNO** * Resistor **R1** terminal **#2** to ground **GND** * Transistor **TIP** base terminal **#1** to **R2** resistor terminal **#2** * Resistor **R2** terminal **#2** to pin **D#9** on the Arduino **UNO** * Transistor **TIP** collector terminal **#2** to diode **D1** collector (negative) terminal **#1** * Transistor **TIP** emitter terminal **#3** to ground **GND** * Diode **D1** anode (positive) terminal **#2** to **9V** * Motor **M1** terminal **#1** to diode **D1** anode **#2** * Motor **M1** terminal **#2** to diode **D1** collector **#1** Connect the 9V battery (+/-) to the bottom breadboard power supply line, and connect 5V and GND pins from the Arduino UNO to the top breadboard power supply line. Connect ground of both breadboard supply lines. ![Breadboard Setup](arduino_dc_motor/breadboard.jpg) #### Code ```c #define BUTTON 2 #define MOTOR 9 void setup() { pinMode(BUTTON,INPUT); pinMode(MOTOR,OUTPUT); } void loop() { if(digitalRead(BUTTON) == HIGH) { analogWrite(MOTOR,255); delay(200); } delay(1); } ``` #### Measurement | | Voltage Drop | |------------------------------|--------------| | **R2** resistor | 3.02V | | **TIP** collector-base | 1.34V | | **TIP** collector-emitter | 0.64V | | **M1** motor | 7.81V | | | Current | |------------------------------|---------| | **TIP** base | 1.5mA | | **TIP** collector | 15.02mA | If the motor shaft is blocked (can not continue to rotate) the **stall current** peaks at 105.5mA at the **TIP** collector.