running LED's off a vex controller

help me please!!!
i need to know how to control a couple of high intensity LED’s of the controller. the reson is i’m making a animatronic robot that uses vex motors and controller for a TSA state compotition and i need the mouth (made of aformentiond LED’s ) to be sincronized to the speech and if it helps I am very good in the fiedls of elctronic parts and circitry

Take your LED and connect the anode to the +5 volts (center contact in the digital ports) connect the cathode to a current limiting resistor with a value between 470 ohms and 1,000 (1K) ohms, and the other end of the resistor to the signal contact (inner contact). Set the digital port up for output and toggle the port to turn the LED on and off.

DO NOT CONNECT THE LED TO SIGNAL AND GROUND. The PIC chip won’t be able to drive the LED to turn it on.

(Edited to add: One/two LED’s per port, if you are doing a huge face, spread the LED’s across the ports. While the PIC can sink current for the LED, don’t get carried away)

Just a couple things to note:

The VEX Microcontroller already has a 1KΩ current limiting resistor on each I/O port (see schematic). This means you can hook the LEDs directly to the port pins as Foster describes without the limit resistor.

Second, the 1KΩ resistance limits the signal power per port to around 4mA. This is not enough to drive your high intensity LEDs as brightly as you’d probably like. You can wire multiple I/O ports in parallel to increase the current drive.

If you need to drive more current, then you will need to add some electronics. The simple transistor switch here will allow you to drive up to the full 1A that the VEX Microcontroller can provide.


  • Dean