Using the V5 3-Wire LED Indicator


The LED (light-emitting diode) Indicator is a device which can provide visual feedback. The LEDs come in red, yellow, and green colors.

The LED Indicators are compatible with the V5 Robot Brain or the Cortex. The LED Indicator can be inserted directly into the Brain. However in most cases, the LED can be seen better when it is used in combination with a 3-Wire Extension Cable, so it can be placed in a highly visible location on the robot. The connection between the extension cable and the LED indicator should be wrapped with an electrical wrap to secure and insulate the connection. The LED Indicator can be attached to a piece of structural metal using zip ties.



When the LED Indicator is used with a 3-Wire Extension Cable it is essential for the Indicator to be inserted correctly. The LED’s outer pin needs to be aligned with the 3-Wire Extension Cable’s outside white (Signal) wire and the center pin needs to be aligned with the red (+5V) wire as the two components are connected.

In order for the LED Indicator to be functional with the V5 Brain, the sensor or its Extension Cable needs to be fully inserted into a V5 Brain 3-Wire Port.

The LED Indicators can be purchased as a pack here.

LED Indicator LED Indicator 3-Wire & Extension Cable
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How the LED Indicator Works

The LED Indicator operation is perhaps one of the simplest of all the 3-Wire devices. A user program can send a “set LED on” command to the V5 Brain and LED will receive power. The program can also send a “set LED off” command and the LED will turn off.

Set LED on Set LED off
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This requires the LED indicator to be paired with a programming language such as the VEXcode V5 or VEXcode Pro V5 to create a user program.

Common Uses of an LED Indicator:

Some of the applications for the LED indicator include: indicating a user program is functioning correctly (troubleshooting a program), verifying the state of another sensor, or providing visual feedback that a condition on the robot has been reached.

Indication within a user program: An LED Indicator can be substituted for an output in a program to provide a safe visual cue. For instance, an LED Indicator could be substituted for a Pneumatic Solenoid Driver to test a user program. In this case, the LED could light up rather than a Pneumatic Cylinder randomly firing if the program’s logic is not correct.

Pneumatic Solenoid Driver and Pneumatic Cylinder

A fun classroom activity to introduce some beginning programming concepts is to model a timed stoplight using LED Indicators. A red, a yellow, and a green LED Indicator can be taped down to a surface in the sequence of a stoplight. Then challenge the students to create a user program which simulates a stoplight.

Verification of a sensor: A common use of an LED is to verify a sensor has provided an expected reading. For example, an Ultrasonic Range Finder could be paired with an LED Indicator. The LED could be programmed to light up when an object (like a sheet of cardboard) is moved to a specific programmed distance (target) from the Range Finder. The distance between the Ultrasonic Range Finder and the object can be measured when the LED turns on. The target distance can then be compared to the actual measured distance and adjusted if necessary.

Another fun classroom programming activity is to simulate a popular electronic logic toy. Again, a red, a yellow, and a green LED Indicator can be taped down to a surface, but this time each LED is paired with a Bumper Switch v2. The program will briefly light up an LED, then the player needs to press the corresponding Bumper Switch. After the switch is pressed, an additional LED will be added to the sequence, briefly lighting up after the first LED lighting is repeated.

Each time the sequence of lights is matched with the correct sequence of pressing the Bumper Switches, an additional light is added to the sequence. This continues until the player wins by matching all the series of programmed lights or the sequence of Bumper Switches pressed does not match the sequence of lights and the game is over.

Checking a robot’s condition: An example of checking a condition can be provided with another classroom activity. In this case, a robotic conveyor belt system could be assembled to model a sorting system used in many workplaces.

A Bumper Switch could be used to start and stop the conveyor belt. A green LED Indicator could be programmed to flash several times after the Switch has been pressed and before the conveyor starts. The green LED could stay on while the conveyor is on and then turn off and a red LED turned on when the conveyor belt is stopped by pressing the Bumper Switch again.

Uses of an LED Indicator on a Competition Robot:

The V5 system has an excellent system of providing customized visual/text feedback between the V5 Brain and the LED screen on the operator’s V5 Controller. Nonetheless, there may be instances where an operator and/or a team coach may not want to take their eyes off of the robot during a match and a well placed LED indicator could provide some excellent visual feedback. Some examples of using LED Indicators on a competition robot are:

Achieving a target: As mentioned before an LED Indicator could be used to indicate if a sensor has reached its target value. A good example of this is when a flywheel is used to throw a ball. The V5 Smart Motors can be set to achieve a specific RPM speed. However, there can be a time delay between the start of the motor and when it is up to speed. An LED Indicator could be turned on to visually communicate when the flywheel is at the target speed for the range the ball needs to be thrown.

Indicating Game Piece position: Some conveyor or slide system designs make it very difficult to visually see the location of a game piece within the system. In this case, a Vision Sensor, Light Sensor, or Line Tracker could be paired with an LED Indicator. When the sensor detects the game piece is in its target position, the LED could be turned on providing the necessary visual feedback.

No matter what the application, the simple-to-use LED Indicator can provide some very useful visual feedback!

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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