LED Matrix

The LED Matrix is a board consisting of 32 RGB LEDs connected in parallel that light up together to display the current status of the robot, such as if it's running autonomously, being tele-operated, etc.

The LED Matrix receives 24V power from the Power Distribution Board, as well as 3 PWM signals from the PDB's microcontroller. These signals control the red, green, and blue lighting of all the LEDs respectively. 

Calculations

LED Resistance:

• Red LED voltage drop: 2.1V
  • Resistance for red LEDs: R = (24V - 2.1V)/5mA = 4380Ω
• Blue/green LED voltage drop: 3.1V
  • Resistance for blue/green LEDs: R = (24V - 3.1V)/5mA = 4180Ω

Resistor Power:

• Red LED resistor voltage drop: 21.9V
  • Red LED resistor power: P = 21.9V * 5mA = 0.1095W
• Blue/green LED resistor voltage drop: 20.9V
  • Blue/green LED resistor power: P = 20.9V * 5mA = 0.1045W

Changelog

• Changed 1kΩ 1/8W 0805 resistors to 4.3kΩ 1/2W 1210 resistors to reduce the current in the LEDs in order to lower the brightness
• Screw terminals were replaced with a single MOLEX connector for convenience
• Replaced FDN337N SuperSOT-3 MOSFETs with DMN3067LW SOT-323 MOSFETs due to old part being out of stock

LEDs

• MPN: ASMB-MTB1-0A3A2
• Datasheet
• Digi-Key link

Project Documents

• GitHub link
• Google Drive Folder

Designers

• Farris Matar - Schematic Capture and PCB design - far-mat42

Built With

• Altium Designer - The PCB design software used

Errata

• Swap 3A fuse for one with a lower current value