What is ULN2003 ?

In electronic projects, it is often necessary to control motors, relays, LEDs, or other high-current loads using microcontrollers (Arduino, PIC, STM32, etc.). However, driving such components directly from microcontroller pins is not possible due to insufficient power and can also cause hardware damage.

This is exactly where the ULN2003 IC comes into play!

ULN2003 is a driver IC that contains 7 Darlington transistor pairs inside. Each channel takes a low-current input signal and provides high-current/high-voltage outputs, allowing it to drive devices such as motors, relays, and lamps.

Main Features:

• 7 channels (7 inputs, 7 outputs)

• Up to about 500 mA output current per channel

• Up to 50V output voltage

• Inputs are TTL/CMOS compatible (can be directly controlled by a microcontroller)

• Built-in flyback diodes (protection for inductive loads)

• Open collector output structure

• Available in different packages such as DIP-16 and SOP-16

How Does It Work?

The Darlington transistor pairs inside the ULN2003 allow a small input current to produce a much larger output current.

In short, the operating principle:

1. The microcontroller sends a "HIGH" (1) signal to one of the ULN2003 input pins.

2. This signal makes the corresponding Darlington transistor pair conductive.

3. A current path forms from the ULN2003 output pin towards ground.

4. Thus, the connected load (for example, a relay coil) is activated.

5. Note: ULN2003 has an open collector output, meaning loads are connected to the VCC side and the IC sinks current to ground.

Application Areas

The ULN2003 IC is very versatile and can be used safely in many electronic projects.

1. Relay Driving

• Microcontroller pins cannot drive relays directly.

• ULN2003 provides sufficient current to the relay coil and includes diode protection to protect the circuit from back EMF generated by the relay.

2. Stepper Motor Driving

• It is especially common with 28BYJ-48 5V stepper motors.

• The ULN2003 energizes the motor coils in sequence to achieve rotation.

3. LED and Lamp Control

• LED panels, signal lamps, or high-power LEDs can be driven with ULN2003.

4. Solenoid and Valve Control

• Electrically controlled mechanical valves can also be managed through the ULN2003.

5. Advertising Panels and Display Systems

• When multiple loads need to be controlled, ULN2003 provides an ideal solution.

Which Version Should I Choose?

There are various versions of the ULN2003 produced by different manufacturers:

• ULN2003A: The most common and standard model

• ULN2003AFWG: Toshiba-made, surface-mount (SOP)

• ULN2003G: RoHS compliant, produced by manufacturers like ON Semiconductor

If you will be soldering manually, choose the DIP-16 package (ULN2003A). Surface-mount (SOP) models require SMD soldering.

Conclusion

ULN2003 is a reliable and powerful driver solution for electronic projects. It allows you to easily control various loads such as relays, stepper motors, and lamps. Affordable, easy to obtain, and versatile, this IC is suitable for both hobby circuits and industrial applications.

If you are working with Arduino or another microcontroller, ULN2003 is definitely a must-have component in your toolkit.