Just finished my first custom PCB build — a few observations

Congrats on getting there, that first board that actually powers on is a good feeling. Mine took three spins before I had one I was happy with, and the thing that bit me hardest was placing the module right next to a ground pour without leaving clearance around the antenna. Wi-Fi range dropped to almost nothing til I cut the keep-out area properly, so check that before you finalize anything if you're using a module with an onboard antenna. Your point about verifying power draw when everything wakes up at once is spot on. I had a situation where my sensors and the radio all spiked during boot and the regulator would brown out randomly. Took me ages to figure out it was a peak current thing, not a wiring mistake. Adding a bigger bulk cap near the module sorted it. On the layout learning curve, what helped me was doing a paper sketch of my sections first, power in one corner, the radio far from the noisy stuff, sensors grouped where the wires come in. Once I stopped routing trace by trace and started thinking in zones, the whole thing came together way faster. Also, order a few spare boards. I guaranteed myself at least one fried board per revision by being careless with the soldering iron, and having spares meant I didn't have to wait two weeks to try a fix.

Funny thing, my expirience went the other direction after my first couple boards. The tidy single board felt amazing for about a month, then I swapped one of the sensors for a newer model and realized I had locked myself in. No way to adapt without cutting traces and bodging wires everywhere, which undid all that neatness fast. Now I design in a row of header pins for anything I might want to change, even if it looks less clean in the photos.

I also stopped fighting with hand layouts and just send everything to a cheap fab house in China. Two layers, solder mask, silkscreen, the works, and it shows up in two weeks for less than what I used to spend on coffee. The first one I ever ordered back in 2019 was about five bucks shipped and I was amazed it worked at all. One thing I'd add on the power side, since you checked simultaneous sensor draw. I got caught once by a sensor's startup surge being way higher than its running draw, and the brownout only showed up intermittently, which drove me nuts for a week. Adding a bigger bulk capacitor near the sensor rail sorted it, but I only found it by staring at the board with the enclosure closed, because the temperture inside shifted things just enough to trigger it.

I've been trying to fit all the small parts onto one of these boards and it is getting super crowded. Trying to get everything to sit close togehter feels like a massive jigsaw puzzle where the pieces don't quite fit. I used a different type of tiny sensor and my whole layout had to shift around to make room. It gets stressful when you are trying to keep all the wires neat and organized. How do you decide where to put the big chip versus all the little pieces around it?

The whole PCB thing is fine, but you gotta remember the days before all this tiny footprint stuff. I always started with the cheap development kits and modules because you just needed to see if the logic worked before you spent time drawing layers and routing traces. That prototyping stage felt way more brutal, wrestling with jumpers and breadboard spaghetti. If the concept didn't hold up on those simple modules, then no amount of careful component placement was gonna save the project anyway.

Switching from a single layer to a two-layer board made a huge difference in my noise issues. I actualy saw signal integrity improve by about 15 percent once I implemented a solid ground plane on the back side. That helps keep the wireless comms clean. I usally keep my power distribution simple, using just one inductor and cap combo for all my peripherals. It keeps the BOM low and the assembly simple.

Update: still going strong after a couple weeks. Took the antenna advice and shifted the wireless module away from the pour with a clear zone around it, range is solid now. Also added spare pads near each sensor after reading the point about getting boxed in when swapping parts later. Saved myself a future headache.