Powering LED's for decoration

Hi all,

It was recently ruled that LED strips are can be used as decoration as long as you power them legally (you can’t use a separate battery solely for LED power)


My students really want to put some LED strips on the robot…just for looks. I would love for them to do this because they can learn some new things along the way. How could this be done without risking damage to the cortex?

From what I found here…


The analog and digital ports share a 5v regulator rated at 1A. If each LED is 20ma then you could in theory power 50 LED’s. But obviously other any sensor used would take away from the available current.

I guess my question is how much power of the 1A do sensors really use? We have 2 sonars, 3 line followers, and some limit switches. We have encoders, but they are IME’s so it appears that they get power from a different source based on the schematic linked above.

So…Is this even possible? Is there a different way to power the LED’s in a legal way? (a motor port, I2C, UART?)

I am far from an electrical engineer, so any guidance would be appreciated.


*I’m by no means an electrical expert, but it seems like any necessary changes would require modification to electrical components, which is unfortunately illegal.

Although I would personally love LED strips to be legal, in the past, teams have only powered them off-the-field by a 9 Volt battery or something along those lines.*

EDIT: I’ve recently been informed that I may be wrong. Disregard everything I said above XD

If you’ll excuse me, I’m going to go order a ton of LED strips.

Guessing here,

limit switch uses close to 0.
sonar, my guess 30-50mA each.
line follower, probably 20mA each.

pneumatic solenoids use the most at 100mA each.

You probably have 800mA available BUT I wouldn’t use all of that as cooling of the regulator is a bit unknown, lets say 500mA. There are many bright leds available that use less than 20mA, you can also put more than one in series and not waste power in the current limit resistor.

IMEs and UART pull power from a different regulator as the diagram shows. Best place would be to use a 3 wire motor port as that is unregulated battery power, I would still keep current to 1A or lower.

We have a string of 20 LED’s on our robot for pure looks. We powered them with a vex legal, and unmodified, two-wire cable plugged into a sensor port. As far as I Know they required no programming, and they have plenty of current to run at full brightness even with 2 limit switches, a pneumatics solenoid, a accelerometer, and a gyroscope. Best of luck to you all.

Just to clarify for people that don’t know…you can purchase LED strips that are already wired with a 3 wire fubota type end which will plug right into the cortex. They are common on hobby websites for things such as quadcopters and the like. Just make sure you get get the right voltage for your application. If you are going to use the digital/analog ports then you need 5v, if you are going to run off of the motor ports then you need 7.2(ish)

I’ve been browsing the web and I’m having trouble finding ones that would work right out of the box with the cortex. Can someone please post a link of where we can find these?

This isn’t an LED “strip”…but same thing.


where did you get your led lights? I can’t find any that I could plug in to the cortex.

Do you have a link where you purchased them?

I would like to find ones that work with the cortex and can change colors between red and blue. if that’s even possible.

There are many out there…I posted a link earlier in this discussion to a ring of leds that would work perfect.

Here is another link to a led strip that would work…


There are lots of them out here, takes some digging and proper search terms though.

You will need to purchase a color changing RGB LED. It is a single clear package with two leads you solder tour wires to. You will not have control of the flash sequence as it is a fixed controller inside the LED that flashes the light. This is the same LED inside a lot of kids toys or even flashy ink pens etc… They are sold by many vendors such as electronix express. These typically require more supply voltage to illuminate than your standard red or green simple LED.

have you found a blue strand that works with the cortex?