# Arduino Lesson 5. The Serial Monitor ## Overview In this lesson, you will build on lesson 4, adding the facility to control the LEDs from your computer using the Arduino Serial Monitor. The serial monitor is the 'tether' between the computer and your Arduino - it lets you send and receive text messages, handy for debugging and also controlling the Arduino from a keyboard! ![](https://cdn-learn.adafruit.com/assets/assets/000/002/178/medium800/learn_arduino_summary.png?1396780242) For example, you will be able to send commands from your computer to turn on LEDs. In this lesson, you will use exactly the same parts and a similar breadboard layout as Lesson 4. So, if you have not already done so, follow lesson 4 now. - [Next Page](https://learn.adafruit.com/adafruit-arduino-lesson-5-the-serial-monitor/the-serial-monitor.md) ## Featured Products ### USB Cable - Standard A-B [USB Cable - Standard A-B](https://www.adafruit.com/product/62) This here is your standard A-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Arduino, USBtinyISP (among other things). 3 feet / 1 meter long Color may vary! In Stock [Buy Now](https://www.adafruit.com/product/62) [Related Guides to the Product](https://learn.adafruit.com/products/62/guides) ### Diffused Red 5mm LED (25 pack) [Diffused Red 5mm LED (25 pack)](https://www.adafruit.com/product/299) Need some indicators? We are big fans of these diffused red LEDs, in fact we use them exclusively in our kits. They are fairly bright so they can be seen in daytime, and from any angle. They go easily into a breadboard and will add that extra zing to your project. - Pack of 25... 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LCD Displays - Part 2](https://learn.adafruit.com/adafruit-arduino-lesson-12-lcd-displays-part-2.md) - [Arduino Ethernet + SD Card](https://learn.adafruit.com/arduino-ethernet-sd-card.md)