Consultation for Final PCB and Circuit Schematic Design (Fire Alarm Sensor Node)

Hello guys from the Arduino Forum.

This post marks the completion of our project's hardware component which I was working on for more than 4 months already, and tomorrow or perhaps the other day I would be submitting its final PCB and schematic design.

Honestly, I still feel deeply anxious on the overall design since I have no experience in any hardware and everything else I did was out of the dire need to complete the project. I also believe I completed it in a funny way where I will mount some ready-made modules on the PCB, as someone told me. It just felt like I was going to waste time to start things from scratch if I did it the other way around.

Is there any place where I could ask some questions or have someone quickly point out rules of thumb that I could apply for the design of our PCB and some of its electronics?

I've been reading books and sources as well but I just want anyone else with experience to assure me that what I've been doing so far is right on track. My anxiety keeps me from submitting the PCB design to the fabrication facility.

Sorry for the long post. Thank you. I'm not forcing anyone to answer my question. I do understand that this will take some of your time, and it's okay if you don't answer.

Post your PCB design and schematic and I'm sure someone will look at it. You can make pictures easy for people to vies by attaching and embedding them following these instructions:

Here they are. The PCB layouts were the only ones I was able to convert to .png by opening the pdfs and using the Snipping Tool. The sch files became blurry by that so I just attached their pdf form. Should that suffice?

I am still about to place power and ground planes but I'm quite unsure about grounding them to the same plane since I have voltages in the circuit around 24 (buzzer), 9 (smoke detector), 5 (MCU, sensor, XBee, etc), and 3.7V from the battery itself which is Li-ion. I'm also thinking about possible noise for the battery analog reading that's why I'm still kind of hesitant to not isolate the battery GND, though it seems I already tied it to the same ground.

lower_schem.pdf (54.1 KB)


upper_schem.pdf (55.6 KB)


Fixed images

Good morning guys. I'm sorry. Should I try to submit the PCB design right now and have a single set fabricated? Perhaps I still could revise it, but yeah it's the cost I'm worried about. I'll just have to share any concern I find with it once it's done with some testing. What do you guys think?

Go for it. Set of PCBs from will cost you $10 each plus shipping, not much cost at all.
If you find a mistake, thru hole parts are easy to change values, or you can use sockets and socket strips for them all.
Cut a trace or two and add a wire or two will be fairly easy as well.

layouts were the only ones I was able to convert to .png by opening the pdfs and using the Snipping Tool. The sch files became blurry by that so I just attached their pdf form.

Pardon the hijack, but what did you use to produce these layouts? , what is an sch file? was the PDF an export from the design tool?

I think I'm getting too old to wire proto boards, but I'm afraid it probably means that I'm too old to use a PCB CAD.

Nahh the fabricator has lots of that. They will provide everything for the creation of the PCB. But yeah, I only considered using through hole resistors and caps. :smiley: Will also be using sockets for the IC and Pro Mini.

I used EagleCAD. I think an .sch file is the file produced by Eagle when you're creating a circuit schematic, while .brd for PCB layouts. The pdf is an export, yes but it is produced using the "Print" option, weirdly. :slight_smile:

Time to learn how to make a ground polygon, so you don't have to draw any ground traces.
Try this:
Click on the polygon icon, and draw a closed square on the outline of the board (top and/or bottom layer).
Box is now a dotted line.
Right-click the polygon line, and click 'name', and name it 'GND'.
Click on the green cross (ratsnest), to flood-fill and connect every ground together.


Thanks! I knew that already and I was just aiming to let you guys see a visible image of what I was doing for the other connections. The PCB is on its way for fabrication and its just a prototype. Hopefully it works. And hey, I already added some karma to most of you guys. Thank you from the very beginning. I've spent most of my time learning about actual electronics here on Arduino, even though it seems that I just keep on asking questions and never even bothered answering one. It's just that someone else who knows better than me answers earlier than I do. I'm now on my casing design using Fusion 360 and it's almost finished, and I just started a few days ago. I might ask again about it on PG. Sorry for the long reply. :smiley: