Do you want to learn how to use 7-segment display LED's? Here you will learn how to build retro-style displays with 7-segment LED's. Shown is how these displays work, how to multiplex them to get an array of digits, and the code to display a 0-20 VDC volt meter and thermometer.

Other useful tutorials
Temperature sensor shootout:    • Temperature sensor shootout  
Writing and reading to SD cards:    • Tutorial: Writing and reading to SD c...  
Saving settings even during MCU power down:    • Tutorial: How to save settings to MCU...  
Getting those darn TFT LCD displays to work:    • Tutorial: Getting TFT LCD displays wo...  
Turning stuff on or off:    • Tutorial: Use your MCU to turn stuff ...  
Writing analog signals/voltages:    • Tutorial: Use analogWrite to vary spe...  
Using digital sensors:    • Tutorial: Use digitalRead to monitor ...  
Using analog sensors:    • Tutorial: Use analogRead to monitor a...  
Talking to your Arduino:    • Tutorial: How to talk to your Arduino...  

Some fun projects to build
Build a 3D printer filament meter:    • Build a 3D printer filament meter  
Homemade motorized table saw fence    • DIY motorized table saw fence  
High"er" res homemade Thermal Camera for $100:    • DIY high-er res Thermal Camera for $100  
DIY Garage Parking Assistant:    • DIY Garage  Parking Assistant