Why do bot builders keep there wires loose in stead of using a PCB to mount all there electrics to
expensive, custom, fragile/non-compliant, etc etc. some people have done it particularly in higher weight classes but it’s not worth the extra hassle for most cases.
also moved this topic to questions and help as this is not a thread about a build.
Mostly cost but also it is worth considering the amount of force applied to a PCB mounted component during an impact. Not just a direct impact from a weapon but the shockwave through a board when hitting a wall etc.
Most mounted components rely on either very small mechanical constrain or just a solder joint. You will see larger components with epoxy around the base or dampening material to help dissipate energy (like in a car crash with crumple zones etc.).
Another reason is repairability, where reconnecting a wire cut by a spinner is possible, and more wire can be added if it’s now too short, with a PCB you pretty much would have to replace the entire thing if it was directly struck and a connection broke. At least that’s my understanding.
Some of us do this! My beetleweight Fatal Deviation has every electronic component (except the receiver, drive motors, and weapon servo) integrated onto one PCB. I did a (very) big writeup on it in the build thread here: Fatal Deviation, my over-engineered beetleweight - #41 by IrregularJoe
I do it because I get a kick out of putting together a really compact and tightly integrated robot, so being able to make a custom PCB that fits a space exactly and puts all the connectors and solder pads in just the right spots is a big draw. I like to have the opportunity to run custom software on my robots so I can play with concepts like electronic stability control. I can calculate every component rating, so I know 20A really means 20A and not “Aliexpress 20A”. Also RGB underglow.
The big downside is that to do it properly, in a way that doesn’t just introduce a bunch of risk and cause your robot to blow up all the time*, takes a bunch of time. There’s probably at least 40 hours in Fatal Deviation’s PCB, and that’s the complete version 2 redesign. If you do go this route expect to need multiple revisions - I have designed many dozens, maybe hundreds of PCBs at this point and still only get it right on revision 1 some of the time. There’s often a bodge wire or a software hack to make things work.
*I am very proud of my record of never having experienced an electrical or electronic failure in the arena, but if the Hockey Pucks of Death meltybrain discord server is anything to go by, it will blow up, a lot. It takes everyone a few goes before they have something that doesn’t blow up sometimes.
Having said all that, if anyone is considering designing their own robot electronics it is a fun challenge and it does let you do things you couldn’t otherwise*. I will disagree with some of the other comments about mechanical robustness too - there’s nothing special about the PCBs that make up an ESC or receiver and they (usually) handle combat just fine. You just have to be sensible about component sizes, how you attach wires (copy the ESCs and receivers you like), and soft mount things as best you can (always a good idea). Electrical and thermal robustness is another story, and that’s the harder part IMO.
*I used the drive PCB as a frame rail in Ultimate Ninja which is going go to really well or really badly we’ll find out as soon as JLC ship my damn parts.