Using a transistor to control high current loads with an Arduino

 const int transistorPin = 9;    // connected to the base of the transistor

   // read the potentiometer:
   int sensorValue = analogRead(A0);
   // map the sensor value to a range from 0 - 255:
   int outputValue = map(sensorValue, 0, 1023, 0, 255);
   // use that to control the transistor:
   analogWrite(transistorPin, outputValue);

Write a quick program to test the circuit. Your program should make the transistor pin an output in the setup method. Then in the loop, it should turn the motor on and off every second, just like the blink sketch does.

const int transistorPin = 9; // connected to the base of the transistor

 void setup() {
   // set  the transistor pin as output:
   pinMode(transistorPin, OUTPUT);
 }

 void loop() {
   digitalWrite(transistorPin, HIGH);
   delay(1000);
   digitalWrite(transistorPin, LOW);
   delay(1000);
 }

Now that you see it working, try changing the speed of the motor or the intensity of the lamp using the potentiometer.

To do that, read the voltage of the potentiometer using analogRead(). Then map the result to a range from 0 to 255 and save it in a new variable. Use that variable to set the speed of the motor or the brightness of the lamp using analogWrite().

(:toggle question2 init=hide show='I give up, how do I do that?' hide='Let me figure it out':)

 void setup() {
   // set  the transistor pin as output:
   pinMode(transistorPin, OUTPUT);

 void loop() {
   digitalWrite(transistorPin, HIGH);
   delay(1000);
   digitalWrite(transistorPin, LOW);
   delay(1000);

(:sourceend:)

Try this code: (:div class=code :)

 const int potPin = 0;           // Analog in 0 connected to the potentiometer
 const int transistorPin = 9;    // connected to the base of the transistor
 int potValue = 0;               // value returned from the potentiometer

 void setup() {
   // set  the transistor pin as output:
   pinMode(transistorPin, OUTPUT);
 }

 void loop() {
   // read the potentiometer, convert it to 0 - 255:
   potValue = analogRead(potPin) / 4;
   // use that to control the transistor:
   analogWrite(9, potValue);
 }

(:toggle question1 init=hide show='I give up, how do I do that?' hide='Let me figure it out':)

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so:

click the image to enlarge

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so: | click the image to enlarge.

arduino_pot_bb.png arduino_pot_schem.png?

Add a potentiometer

Connect a potentiometer to analog in pin 0 of the module:

arduino_pot_bb.png arduino_pot_schem.png?

(Diagram made with Fritzing)

Add a potentiometer and LED

Connect a potentiometer to analog in pin 0 of the module, and an LED to digital pin 9:

(Diagram made with Fritzing)

Connect a transistor to the microcontroller

The transistor allows you to control a circuit that's carrying higher current and voltage from the microcontroller. It acts as an electronic switch. The one you're using for this lab is an NPN-type transistor called a TIP120. The datasheet for it can be found here. It's designed for switching high-current loads. It has three connections, the base, the collector, and the emitter. The base is connected to the microcontroller's output. The high-current load (i.e. the motor or light) is attached to its power source, and then to the collector of the transistor. The emitter of the transistor is connected to ground.

http://itp.nyu.edu/physcomp/images/labs/tip120_pinout.png
Pinout of a TIP-120 transistor, from left to right: base, collector, emitter.

http://itp.nyu.edu/physcomp/images/labs/npntransistor.gif
Note: you can also use an IRF510 or IRF520 MOSFET transistor for this. They have the same pin configuration as the TIP120, and perform similarly. They can handle more amperage and voltage, but are more sensitive to static electricity damage.

click the image to enlarge

 click the image to enlarge

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so: | click the image to enlarge.

Connect a lamp instead

You could also attach a lamp using a transistor. Like the motor, the lamp circuit below assumes a 12V lamp. Change your power supply accordingly if you're using a different lamp. In the lamp circuit, the protection diode is not needed, since there's no way for the polarity to get reversed in this circuit:

click the image to enlarge

arduino_transistor_lamp_schem.png?

arduino_transisr_lamp.png?

arduino_transistor_lamp.png?

<<<<<<<

=======

>>>>>>>

Attach:arduino_por_schem.png Δ Δ

Note: the schematic symbol for the transistor here is actually
for an IRF510 MOSFET. But it can be replaced with a TIP120

Note: the schematic symbol for the transistor here is actually for an IRF510 MOSFET. But it can be replaced with a TIP120

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so: .

A motor controlled like this can only be turned in one direction. To be able to reverse the direction of the motor, an H-bridge circuit is required. For more on controlling DC motors with H-bridges, see the DC Motor Control lab

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so: .

(:table:) (:cellnr:) http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_schem.png (:cell:)

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so: diode.png.

FInally, add diode in parallel with the collector and emitter of the transistor, pointing away from ground. The diode to protects the transistor from back voltage generated when the motor shuts off, or if the motor is turned in the reverse direction.

Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic, like so: diagram.

Attach a DC motor to the collector of the transistor. Most motors will require more amperage than the microcontroller can supply, so you will need to add a separate power supply as well. If your motor runs on around 9V, you could use a 9V battery. A 5V motor might run on 4 AA batteries. a 12V battery may need a 12V wall wart, or a 12V battery. The ground of the motor power supply should connect to the ground of the microcontroller, on the breadboard.

Connect a motor and power supply

Attach a DC motor to the collector of the transistor. Most motors will require more amperage than the microcontroller can supply, so you will need to add a separate power supply as well. If your motor runs on around 9V, you could use a 9V battery. A 5V motor might run on 4 AA batteries. a 12V battery may need a 12V wall wart, or a 12V battery.

Connect a transistor to the microcontroller

Note: you can also use an IRF510 or IRF520 MOSFET transistor for this. They have the same pin configuration as the TIP120, and perform similarly. They can handle more amperage and voltage, but are more sensitive to static electricity damage.

Connect the base to an output pin of the microcontroller, and the emitter to ground like so:

http://itp.nyu.edu/physcomp/images/labs/arduino_pot_schem.png

[|]]

 int potValue = 0;               // value returned from the potentiometer

(:div class=code :)

 const int potPin = 0;           // Analog in 0 connected to the potentiometer
 const int transistorPin = 9;    // connected to the base of the transistor
 const int potValue = 0;         // value returned from the potentiometer

 void setup() {
   // set  the transistor pin as output:
   pinMode(transistorPin, OUTPUT);

 void loop() {
   // read the potentiometer, convert it to 0 - 255:
   potValue = analogRead(potPin) / 4;
   // use that to control the transistor:
   analogWrite(9, potValue);

(:divend:)

(:div class=code :)

 const int transistorPin = 9;    // connected to the base of the transistor

 void setup() {
   // set  the transistor pin as output:
   pinMode(transistorPin, OUTPUT);
 }

 void loop() {
   digitalWrite(transistorPin, HIGH);
   delay(1000);
   digitalWrite(transistorPin, LOW);
   delay(1000);
 }

(:divend:)

 int transistorPin = 9;    // connected to the base of the transistor
 int potValue = 0;         // value returned from the potentiometer

 void setup() {
   // set  the transistor pin as output:
   pinMode(transistorPin, OUTPUT);
 }

 void loop() {
   // read the potentiometer, convert it to 0 - 255:
   potValue = analogRead(potPin) / 4;
   // use that to control the transistor:
   analogWrite(9, potValue);
 }

In the motor circuit below, there is a diode in parallel with the collector and emitter of the transistor, pointing away from ground. This is there to protect the transistor should the polarity of the current reverse (for example, if the motor was turned in reverse, or when it releases back voltage). Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic (diagram).

In the motor circuit below, there is a diode in parallel with the collector and emitter of the transistor, pointing away from ground. This is there to protect the transistor should the polarity of the current reverse (for example, if the motor was turned in reverse, or when it releases back voltage). Be sure to add the diode to your circuit correctly. The silver band on the diode denotes the cathode which is the tip of the arrow in the schematic.

The schematic symbol of an NPN transistor where B is the base, C is the collector, and E is the emitter.

The schematic symbol of an NPN transistor where B is the base, C is the collector, is the emitter.

http://itp.nyu.edu/physcomp/images/labs/tip120_pinout.png
Pinout of a TIP-120 transistor, from left to right: base, collector, emitter.

http://itp.nyu.edu/physcomp/images/labs/npntransistor.gif

The schematic symbol of an NPN transistor

(:title Using a transistor to control high current loads with an Arduino:)

(:title Using a TIP-120 to control high current loads with an Arduino:)

Notes

For the motor users:
A motor controlled like this can only be turned in one direction. To be able to reverse the direction of the motor, an H-bridge circuit is required. For more on controlling DC motors with H-bridges, see the DC Motor Control lab

In this tutorial, you'll learn how to control a high-current DC load such as a DC motor or an incandescent light from a microcontroller.

You will need the following parts for this tutorial.

(:toc Table of Contents:)

Parts

(:toc:)

http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_lamp_schem.png

http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_lamp.JPG

http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_lamp_schem.png

http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_lamp.JPG

%height=300 alt='Arduino TIP120 schematic'%http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_lamp_schem.png (:cell:)

http://itp.nyu.edu/physcomp/images/labs/bb_pot.jpg

http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_schem.png

http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_motor.JPG

http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_schem.png

http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_motor.JPG

http://itp.nyu.edu/physcomp/images/labs/arduino_pot_schem.png

(:cell:)

(:cell:)

(:table:) (:cellnr colspan=2:)

(:cellnr:) %alt='Arduino TIP120 with lamp'%http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_lamp.JPG (:cell:) %alt='Arduino TIP120 with lamp'%http://itp.nyu.edu/physcomp/images/labs/bboard_shield_tip120_lamp.JPG (:tableend:)

http://itp.nyu.edu/physcomp/images/labs/lamp_holder.JPG | Incandescent lamp and socket

http://itp.nyu.edu/physcomp/images/labs/lamp_socket.JPG | Incandescent lamp and socket

%alt='Arduino TIP120 with motor'%http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_motor.JPG (:cell:) %alt='Arduino TIP120 with motor'%http://itp.nyu.edu/physcomp/images/labs/bboard_shield_tip120_motor.JPG

(:table:) (:cellnr colspan=2:)

(:cellnr:) %height=300 alt='Arduino TIP120 with motor'%http://itp.nyu.edu/physcomp/images/labs/bboard_tip120_motor.JPG (:cellnr:) %height=300 alt='Arduino TIP120 with motor'%http://itp.nyu.edu/physcomp/images/labs/bboard_shield_tip120_motor.JPG (:tableend:)

int transistorPin = 9; // connected to the base of the transistor

void setup() {

  // set  the transistor pin as output:
  pinMode(transistorPin, OUTPUT);

}

void loop() {

  digitalWrite(transistorPin, HIGH);
  delay(1000);
  digitalWrite(transistorPin, LOW);
  delay(1000);

}

int potPin = 0; // Analog in 0 connected to the potentiometer int transistorPin = 9; // connected to the base of the transistor int potValue = 0; // value returned from the potentiometer

void setup() {

  // set  the transistor pin as output:
  pinMode(transistorPin, OUTPUT);

}

void loop() {

  // read the potentiometer, convert it to 0 - 255:
  potValue = analogRead(potPin) / 4;
  // use that to control the transistor:
  analogWrite(9, potValue);

}

Connect a motor

Connect a lamp

Program the microcontroller

Here's a quick program to test the circuit:

Now that you see it working, try changing the speed of the motor or the intensity of the lamp using the potentiometer. Try this code:

Note for the motor users:

A motor controlled like this can only be turned in one direction. To be able to reverse the direction of the motor, an H-bridge circuit is required. For more on controlling DC motors with H-bridges, see the DC Motor Control lab

Get creative

http://itp.nyu.edu/physcomp/images/labs/tip120_transistor.JPG | TIP120 transistor

The transistor allows you to control a circuit that's carrying higher current and voltage from the microcontroller. It acts as an electronic switch. The one you're using for this lab is an NPN-type transistor called a TIP120. The datasheet for it can be found here. It's designed for switching high-current loads. It has three connections, the base, the collector, and the emitter. The base is connected to the microcontroller's output. The high-current load (i.e. the motor or light) is attached to its power source, and then to the collector of the transistor. The emitter of the transistor is connected to ground.

This circuit assumes you're using a 12V motor. If your motor requires a different voltage, make sure to use a power supply that's appropriate. Connect the ground of the motor's supply to the ground of your microcontroller circuit, though, or the circuit won't work properly.

Likewise, the lamp circuit below assumes a 12V lamp. Change your power supply accordingly if you're using a different lamp. In the lamp circuit, the protection diode is not needed, since there's no way for the polarity to get reversed in this circuit:

%height=300 alt='Arduino TIP120 schematic'%http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_lamp_schem.png

%height=300 alt='Arduino TIP120 schematic'%http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_schem.png

The simplest program for this would be as follows:

%alt='Arduino TIP120 schematic'%http://itp.nyu.edu/physcomp/images/labs/arduino_tip120_schem.png

Connect a TIP120 transistor to the microcontroller

The transistor allows you to control a circuit that's carrying higher current and voltage from the microcontroller. It acts as an electronic switch. The one you're using for this lab is an NPN-type transistor called a TIP120. It's designed for switching high-current loads. It has three connections, the base, the collector, and the emitter. The base is connected to the microcontroller's output. The high-current load (i.e. the motor or light) is attached to its power source, and then to the collector of the transistor. The emitter of the transistor is connected to ground.

In the motor circuit below, there is a diode in parallel with the collector and emitter of the transistor, pointing away from ground. This is there to protect the transistor should the polarity of the current reverse (for example, if the motor was turned in reverse, or when it releases back voltage).

%alt='Arduino TIP120 schematic'%http://itp.nyu.edu/physcomp/images/labs/arduino_TIP120_schem.jpg

http://itp.nyu.edu/physcomp/images/labs/arduino_pot_schem.png

http://itp.nyu.edu/physcomp/images/labs/arduino_analog_pot_schem.png

http://itp.nyu.edu/physcomp/images/labs/bb_pot.jpg

http://itp.nyu.edu/physcomp/images/labs/shield_pot.jpg

http://itp.nyu.edu/physcomp/images/labs/electrolytic_cap.JPG | 10uF electrolytic capacitor

http://itp.nyu.edu/physcomp/images/labs/1N4004_diodes.JPG | power diodes
(for DC Motor version only)

http://itp.nyu.edu/physcomp/images/labs/1N4004_diodes.JPG | power diodes (for DC Motor version only)

http://itp.nyu.edu/physcomp/images/labs/electrolytic_cap.JPG | 10uF electrolytic capacitor

In this tutorial, you'll learn how to control a high-current DC load such as a DC motor or an incandescent light from a microcontroller.

- or -

http://itp.nyu.edu/physcomp/images/labs/incandescent_lamp.JPG | Incandescent lamp and socket

http://itp.nyu.edu/physcomp/images/labs/1N4004_diodes.JPG | power diodes

http://itp.nyu.edu/physcomp/images/labs/electrolytic_cap.JPG | 10uF electrolytic capacitor

   * 10Kohm resistors

Add a potentiometer

Connect a potentiometer to analog in pin 0 of the module. You'll use this later to control the output, whether it's a motor or a light.

http://itp.nyu.edu/physcomp/images/labs/arduino_analog_input_schem.png

Breadboard version: http://itp.nyu.edu/physcomp/images/labs/bb_pot.jpg

Breadboard shield version: http://itp.nyu.edu/physcomp/images/labs/shield_pot.jpg

Connect a TIP120 transistor to the microcontroller

http://itp.nyu.edu/physcomp/images/labs/potentiometer.jpg | 10Kohm potentiometer

http://itp.nyu.edu/physcomp/images/labs/potentiometer.jpg | 10Kohm potentiometer

In this tutorial, you'll learn how to control a high-current DC load such as a DC motor or an incandescent light from a microcontroller.

For this tutorial you'll need:

http://itp.nyu.edu/physcomp/images/labs/breadboard.jpg | Solderless breadboard

http://itp.nyu.edu/physcomp/images/labs/hookup_wire.jpg | 22-AWG hookup wire

http://itp.nyu.edu/physcomp/images/labs/arduino.jpg | Arduino Microcontroller
module

http://itp.nyu.edu/physcomp/images/labs/leds.jpg | Light Emiting Diodes, LED

http://itp.nyu.edu/physcomp/images/labs/resistors.jpg | 10Kohm resistors

http://itp.nyu.edu/physcomp/images/labs/switch.jpg | switch

http://itp.nyu.edu/physcomp/images/labs/L293_h-bridge.JPG | L293 H-bridge

http://itp.nyu.edu/physcomp/images/labs/dc_power_supply.JPG | DC power supply

http://itp.nyu.edu/physcomp/images/labs/dc_motor.JPG | DC Motor

   * 1N4004 diodes

    * 10uF capacitor 

Prepare the breadboard

Conect power and ground on the breadboard to power and ground from the microcontroller. On the Arduino module, use the 5V and any of the ground connections:

http://itp.nyu.edu/physcomp/images/labs/arduino_bboard_power.jpg

If you're using an Arduino breadboard shield, there is a row of sockets connected to 5V on the analog in side of the breadboard, and a row connected to ground on the digital in side of the board:

http://itp.nyu.edu/physcomp/images/labs/breadboard_shield.jpg

Add a Digital Input (a switch)

Connect a switch to digital input 2 on the Arduino.

(:table:) (:cellnr colspan=2:) http://itp.nyu.edu/physcomp/images/labs/arduino_dig_input_schem.png (:cellnr:) http://itp.nyu.edu/physcomp/images/labs/arduino_switch.jpg
Breadboard version (:cell:) http://itp.nyu.edu/physcomp/images/labs/bbrd_shield_switch.jpg
Shield version (:tableend:)

Minimum parts needed: (new parts in bold. see parts list for details)

    * Prototyping board (breadboard)
    * Power supply connector (2)
    * 5-15VDC power supply
    * Assorted wires
    * 5V regulator
    * BX-24
    * Serial cable
    * DB9 female serial connector & headers
    * LED's
    * Switch
    * 1Kohm resistors
    * 1N4004 diodes
    * TIP120 transistor
    * DC motor
    * power supply for DC motor
    * 10uF capacitor (optional)
    * 1uF capacitor (optional)
    * 10Kohm resistors
    * 220 ohm resistors 

Step 1:

Get a DC motor that runs on low voltage DC, in the 5-15V range. Connect leads to its terminals, and run if from a benchtop power supply in the lab. Try changing the voltage on it, and seeing what effect it has. Don't go over the motor's rated voltage. Connect a switch in series with the motor and use it to turn on the motor.

Step 2:

Connect the base of a TIP120 transistor to one pin of your BX-24. Connect the motor to the transistor as follows:

Note the second power supply. Most motors take a great deal more current than a microprocessor, and need their own supply. The example below uses a 9V battery as a separate power source. Whatever motor you use, make sure the power source is compatible (i.e. don't use a 9V battery for a 3V motor!).

Connect a switch to another pin of the BX-24 and program it to control the motor, like so:

Detail of the board:

Note that we've added two capacitors on either side of our regulator. They smooth out the power, as the motor will cause spikes and dips when it turns on and off.

Here's the schematic for the capacitors and the regulator:

The simplest program fot this would be as follows:

Sub main()

	call delay(0.5)  ' start  program with a half-second delay 

	do
		call putPin(13, getPin(14))
	loop

end sub

If your power supply for the BX24 is compatible with your motor, you can wire the motor supply in parallel with the 5V regulator. For example, I use a 12V DC 1000 mA power adaptor, so I can use a 12V motor, if the power from the motor is wired in parallel with the 5V regulator's input, like so:

Note that the motor and the BX24 need a common ground (in our case, they get it through the transistor's base; see above schematic).

Step 4 (optional step):

A motor controlled like this can only be turned in one direction. To be able to reverse the direction of the motor, an H-bridge circuit is required. For more on controlling DC motors with H-bridges, see the notes on DC motor control. Then get an H-bridge such as the Texas Instruments SN754410, or make your own. Use it to control the direction of a motor.

Step 5:

Use your motor to make something move, vibrate, rise, fall, roll, creep, or whatever you can think of, in response to user input from a digital input device (switch, floor sensor, tripwire, etc).