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submitted 1 day ago by cm0002@lemdro.id to c/memes@sopuli.xyz
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[-] Aceticon@lemmy.dbzer0.com 2 points 3 hours ago* (last edited 1 hour ago)

FYI, the actual circuit properly designed is stupidly simple:

  • The 5V and Ground power lines come in from USB on dedicated pins
  • Since that's a USB-C connector you need 2x resistors for it CC lines (they let the USB Host on the other side know that something is connected to it and wants power of a certain maximum current, and to figure out the orientation of the cable since it can be plugged in two orientations)
  • To light the LED you need the actual LED and a resistor that limits the current that goes to the LED (since LEDs themselves don't limit it and without external current limitation they'll just light up very brightly and then release some "magic smoke" and stop working)

That's it.

Now, assuming R3 and R4 are properly connect CC line resistors (though WHY THE FUCK are the two lines of R3 routed on the other side of the board!!?), the only two other things needed are R1 and D1, nothing else.

Instead, there are way too many extra components, most notably this thing on the middle, supposedly a microchip (judging by the "U" code, can't see the actual writting in the device), maybe a voltage regulator but what would be the point!?

Worse, all 3 legs of that U1 device are wired together. If we're really really lucky, they go nowhere. Otherwise at least one ends up connected to a Ground line (ultimatelly coming from USB) and the other to a power (most likely the 5V from USB) - in other words, it's a short circuit of the power from USB. Not, just not good, but actually a seriously bad "I've never touched electronics in my life" mistake: there is literally no topology where the 3 pins of a 3-pin component are wired together like that, since electrically that's the same as not having it there at all (so even if connected to something else than 5V + GND, at best that component would never do anything). This is like something you figure out in the first hour of learning Electronics.

This shit is not just a little bad, it's incredibly bad and probably a danger to connect to anything over USB.

this post was submitted on 15 Apr 2026
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