Addressable RGB Strips

Hey,

I have some spare RGB strips that I want to place on the bot. To be honest, I wasn’t able to find much documentation as to the connections (I prefer it being powered by the brain, via a smart or 3 pin port), or the code. In addition, what colors would be banned, and will it matter that my specific RGB strips have a 24 Volt rail (i.e. is there a power cap for the V5 Brain)?

Very long story, I’ll type up some info later.

What are the exact specs of your lights?

@TaranMayer,

Not sure exactly what you need, but here is what is on the box:

Power: 36W (although the strips themselves have a 24 rail?)
Brightness: 450 lumens
16 colors

That’s all the box had, hope it helps!

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Could you share a picture of your light strips? I’m not sure exactly what you have.

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Yeah, here are some pics, Ik it’s not a ton of info but it’s what I have.

image image image

we used RGB strips before by soldering it with the old 393 motor controllers, then powered it through the 3 wire port. Id assume you can’t use red or blue in matches since that can mess with color and vision sensors, and cause confusion as to which teams robots which

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Any chance of a wiring diagram, or anything of the sort?

image
This is an arduino, but it looks like you should be able to use 3 ports to control the strip. I don’t think you would need a breadboard as long as you send out the right signals from the brain

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That kinda makes sense, but how would i wire the 4 ports on the led strip to the 2 prongs of the mc 29?

You use a motor controller for RGB, though I’m not sure how you’d ground it. Also this example needs 12v of power which you couldn’t supply from a brain. You could use 1 motor controller to tell an arduino what color to make the strip display, but that would add some complexity

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Edit: See below


You need one Motor Controller 29 for each color channel. Connect the positive outputs of each MC29 to the color channels and any one MC29’s negative output to the ground bus of the LED strip (all the grounds will be tied together anyway).

Note that either output of an MC29 can be the positive output. For simplicity, in your code make sure you only ever drive the MC29s with a positive or zero power level. Determine which output is the ‘positive’ output based on that restriction.

(Disclaimer: this post is not written like a tutorial and will require basic electronics skills to follow)

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Actually… These are 24V LED strips. There is no way you can power them from a V5 Brain.

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That’s seems like it would work. For clarification, would such a method (I.e 3 motor controllers connect to brain) work if all negative ports are linked and connected to the negative terminal of an external powers once, like a battery? If so, what would be considered legal by VEX?

In addition, what would code look like, what instructions would be sent to the motor controllers for the various colors or color cycling?

You are not allowed to use any external power source. Period.

Technically there is a small exception to this rule, but it doesn’t apply in your case anyway. Check the game manual for further details.


As for the code, changing the power level of any individual motor controller will change the intensity of the color it is associated with. 100% power would be full intensity, and 0% would obviously be off.

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Hey, so since my only problem now is power, I did some thinking in MultiSim. (disclaimer, not really all that experienced, only know basic concepts of electronics)

Screenshot 2020-11-18 at 7.54.16 PM

If you ignore the lack of connections for the smart ports and the 3-wire ports for the MC 29s, it should be self-explanatory? I was looking at maybe powering the 24V rail using multiple smart ports, two are only shown, but more could be wired in series to increase the voltage (is it series, if there are multiple “power sources”?). Anyway, appreciate the help so far, and could use some feedback.

Also, I didn’t include the data wires of the smart cables, just wanted to confirm they are unnecessary, since the ports are only providing power?

Firstly, what you have drawn puts two Smart Ports in parallel, not series, and so you are left with the same +12V and 0V available.

However, it is impossible to connect them in series without damaging the electronics (making a slight, but likely, assumption about the circuitry in the Brain — I don’t remember exactly how it’s laid out). This is because all the negatives are connected together and all the positives are connected together inside the Brain.

The only way to get 24V is to use a boost converter circuit, but that seems really overkill for what you’re doing. Furthermore, you can’t run MC29’s at 24V anyway. I would just get a different LED strip if you really want it to work; perhaps get an addressable one based on WS2811 or WS2812 even.

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Okay then. If i were still going to use the same strip, roughly, how would the brightness be impacted?

It would probably be pretty faint. Try connecting 5V or 12V between ground and one of your color channels, and see exactly how it is for yourself.

It’s also worth noting that I’m not 100% sure if MC29’s will even work at 12V, since battery voltage of the Cortex system never exceeded ≈9V.

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