Our team will soon be switching to V5, and we were wondering if it was possible to power strip LEDs with the V5 Brain. If this is possible, could someone please explain how to wire it? I can’t seem to find any straight answers on this subject.
I saw it once at a comp. Is it legal?
Yes, as long as you power it with the VEX power supply. Problem is, I don’t know how to do that.
I’m not sure I would recommend even trying given the relatively fragile nature of current V5 electronics. I personally would stick to functional, first-party electronic components only; that is, motors and sensors from VEX.
With that said, you can probably get enough power for a low-intensity and/or relatively short LED strip from the legacy 3-pin ports: the 2 pins on the outside will have 5V across them, while the center pin would carry data. You would use a multimeter to determine the polarity of the outer pins and correspondingly connect your LED strip to them; the center pin would go unused.
And MOST DEFINITELY heed the warning below from @536Mentor.
I would be VERY careful trying to run it from the legacy ports. Not only are they only 5V, but they are not set up for much of a current draw either.
Hmmm… what type of strip were you planning to use? Typically you have single colour strips or RGB strips that run off 12V, or WS2812B “Neopixel” strips that run off 5V. (And are rather fussy about their 5V, thank you very much.)
The Red and Green of the 12V strips can run at lower voltages, but the blue is pretty fussy about getting at least 10V or so.
The advantage of the 2812B strips is that the LEDs are RGB and individually addressable, allowing you to create cool animations. The disadvantage is that you need to send them a control signal to activate the LEDs… it’s easy from Arduinos as there is a library for that purpose. Perhaps someone needs to create a library for the V5 or Cortex. Actually… a WS2812B/Neopixel driver board would be a really cool product for VEX to come up with. (Once they have a bit of spare time, that is… I understand they’re busy at the moment.)
You do want to keep an eye on current consumption. The 12V strips shouldn’t be too bad as they connect with three LEDs in series, but the Neopixels can draw up to 60mA per LED when set to full white. You can “throttle” the LEDs, selecting only some of them to be on, or using only one colour (full red is about 20mA/LED) or using dimmed colours. If you’re using NeoPixels connected to the V5 legacy ports (they’re at 5V) then you’ve got a maximum of 2A total across all the ports. You should be able to handle 20 NeoPixels at full brightness with no problem. 30 would be pushing it a bit for continuous use, particularly if you’re doing anything else with the ports. https://www.vexrobotics.com/v5-architecture.html
There is less information about the V5 motor ports… in fact I’ve been able to find frighteningly little. We know the motors can handle 2.5A at stall, so each motor port can handle putting out 2.5A fairly continuously I’d assume, but I can’t find a document saying which pins are power and gnd or what the voltage is… should be easy to figure out with a multimeter. I’d guess that the motor port is a fairly direct connection to the battery, so this might be ideal for powering the 12V strips.
I wouldn’t worry too much about using the strips with V5. They’re a fairly passive load… just make sure you don’t go creating short circuits as I haven’t seen anything on what the fusing is like for each of the motor ports. I’m sure they’re protected… well, pretty sure, at least.
It can definitely be done… but why not try lighting your strips using a breadboard (and Arduino for the Neopixels) and power supply first, then reading the specs for your “brain” to see which ports will match the power demands most adequately. This way you’ll also get some experience soldering the wires to make neat, reliable connections before attaching them to your robot. I suspect the V5 is pretty resistant to any damage that might be caused by a bad connection… but if I’m wrong, it is much easier to replace a breadboard and an Arduino than to replace a V5!
But how do you connect the strip to a 3 pin port?
- 1 Futaba-J or Dupont 3-pin housing
- 3 Dupont female pins
- Some wire, with 2 or more conductors
- Some solder (I recommend lead-based for beginners)
- A Dupont crimping tool
- A wire stripper
- A soldering iron
Notes on ordering:
- Virtually all listed items can be found cheaper on sites other than Amazon (Ebay, Ali Express, etc.).
- Significantly cheaper crimping tools and soldering irons are available; these cheaper alternatives will be fine if you do not plan on using them regularly.
- I recommend ordering as much as possible from Robosource to be sure you’re getting the correct items.
- See this thread for more info on sourcing the right parts.
To make the connection, first cut a length of wire 4 inches longer than necessary, just to be safe. If using wire with more than 2 conductors, peel apart any 2 conductors from the rest in the length you cut. Strip about 0.25 inches of insulation from one end of the cut wire. Separate the conductors as necessary and solder these stripped ends onto your LED strip. On the other end, follow the instructions in Robosource’s video to crimp the connectors and place them in the outer slots of the housing.
We found LED strips that has the same connection for the charging port for the V5 batteries. We are wary of overcurrent or the battery breaking, so we don’t know if it would be worth even attempting plugging the LEDs into the battery charging port.
I doubt there would be battery voltage on the charge port anyway. It’s on the wrong side of the charging circuit.
I played around with this for a bit and got something working:
Thanks, that should help. A few questions:
- How did you connect to the brain?
2)What brand are these?
3)Did you have to code these yourself?
4)What parts would I need to replicate this?
USB tester: https://www.amazon.com/gp/product/B01D9Y6ZFW
Strip lights: https://www.amazon.com/gp/product/B06XBY86BR
Motor Controller 29 connected to 3 wire port, USB extension cut up to connect USB cable (you could also just cut the cable on the USB light strip)
Code (such as it is) attached
ledtest.vex (2 KB)
Do you need the usb tester? And what wires go where when soldering?
The usb tester is just for testing. I wanted to see what power draw there was.
You need to connect the power and 5v from the USB wire to the two leads on the motor controller. Depending on what cord you cut open, they may vary in color, but usually they are red (5v) and black (ground). As you might be able to see in the video, I ended up needing to connect red to black and black to red on the motor controller. If it doesn’t work that way, flip it around.
About now is the time I need to say you would do all this at your own risk. It all worked for me, but if you manage to fry your V5 brain trying to do this, that’s on you.
So I would need to cut the USB end off of the cable?
The motor controller isn’t actually necessary. It doesn’t contribute anything in this scenario. You can get 5V directly off of the outer pins of the 3-wire connection.
How do you connect the USB to the mc29?
After some more testing, I was able to get 5V off of the middle pin, with the third pin (furthest down) being ground. I didn’t have the ability to turn it on or off, though, it was just on without a program running. I couldn’t get anything to work on just the outer pins. With the MC29, I can turn the LED strip on and off the way I have it set up.
I cut a USB extension cable, cut back the shielding, stripped the wires, crimped on some pins, and put on a recycled connector housing. You could also recycle a motor or sensor connector if you don’t have the pins.
Could you show a wiring diagram? I am really lost on how to do this. Which of the wires do you crimp to?