I keep being asked how I made my LED strips for the V5 brain. I finally put together a video, so here it is:
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The legacy ports on the V5 brain use a regulated 5V supply for sensors so only relatively small currents can be drawn.
I don’t know if the brain has any kind of over current shutoff or what kind of regulation it uses but if it
uses a simple linear voltage regulator, the power dissipation of the regulator will be the difference between the battery voltage and 5V output multiplied by the current so at one amp the regulator will make (12V-5V)*1A = 7W of heat which would probably do bad thing to the brain after a while.
For small LED strips you’ll probably be OK but it would be a good idea to check the current draw of your LEDs before you use them.
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The lights are 5 volt
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I updated the description with links to the materials and the code on GitHub.
2:00 If you’re just going to chop off the 4-pin end anyway, you have no need for a specific cable. You just need literally any cable with a female USB-A connector on one end.
4:40 You really should not solder or twist together the wires (unless directly connecting to an MC-29 as you mention later in the video). You should crimp new pins on the end of the USB cable and add a housing. If crimped properly, the cable will be much more robust (soldering or twisting creates a weak point in the middle of the cable).
6:08 The light strip really doesn’t need to terminate to a USB connector. This is just an arbitrary choice to make it work with your adapter cable. In reality, virtually any connector will work as long as it provides the 2 pins for +5V and ground and you can electrically connect it to a motor controller 29.
6:48 That’s not strictly true. You could always just resolder a USB connector or other connector to your LED strip.
8:00 VCS text-based, VEXcode text-based, RMS C++, and PROS C++ all share the same language (C++). However, only VCS and VEXcode share the same API.
8:55 For a tutorial like this, it is better to provide the minimum viable code based on the template rather than making unnecessary stylistic changes (moving things to vex.h, changing 1 to true, etc.).
10:09 You should not have definitions in a header file.
It may seem like I am being overly harsh on the video, but I am of the opinion that people needing a video tutorial like this probably should not mess with powering 3rd-party devices off the Brain. You should have a basic idea of electronics and circuits before trying anything like this (partly because of additional considerations like what @marinmersenne mentioned), and, with that basic understanding of electronics and circuits, a video like this then becomes trivial.
For those without the electronics knowledge, you can still put LED strips on your robot. Just use a small USB power bank instead of trying to power your LEDs from the Brain, since that is now legal this season.
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Yes. I understand your concerns, however I made this as a simple way of getting it to work, not necessarily the best way of getting it working. Cable crimping would require tools and parts that not necessarily everybody has. I spent a significant amount of time last year figuring out an easy method of getting this to work, and I am happy with how it turned out.
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