PCB review. THT board, logic components on breakouts. Basic board. - Page 1
Forum section: electronics / beginners

author: visoft
author_rank: Newbie
timestamp: March 09, 2022, 01:52:00 pm
content: Hi!I have a home automation system controlled by a Raspberry Pi. It works, but everything is on breadboards. [Here is a lengthy rant vid about that][https://odysee.com/@ml-visoft:d/08_homeautomation_rants:8?r=BUyjwzCKiXR92SVpmG78hqyauFDrgDAN]This is the existing mess.Anyway, I decided to make a PCB out of [that|some] mess of wires. This would be my first PCB.Here is a screen capture of the current PCB status:The  complete KiCad project (also a 1st) is here:https://github.com/cristi-zz/ha-pcbInhttps://github.com/cristi-zz/ha-pcb/tree/master/pdfsare some pdfs with the board but I can't really plot nice copper layers without all the fillings.The board is THT because I can't really solder SMDs (maybe bigger components) and bc some chips are not available so I will reuse existing ones (on breakout boards).Please take a look and tell me if I screwed sth. ZERO experience in pcb making so I tried to do my best. Both schematic and PCB pass the check rules, PCB clearances are derived fom JLCPCB but I hope I did not push anything to the limit.

author: nvmR
author_rank: Regular Contributor
timestamp: March 09, 2022, 02:30:29 pm
content: Hi visoft,Very cool for a first board!Just a few things off the bat that I thought about.1) Try to label your PCB with a name and revision number.2) Are your RJ45s vertical? If not, move them towards the edge, it will be easier to get the cable out.3) Try to label #1 pin of each connector, with a #1 or a dot.4) Rounded edges look quite pretty on PCBs, and cost the same.5) For not much more money, you can make the PCB bigger, and attach the Raspberry Pi to the board mechanically. If you get craftier, you can attach the Raspberry pi directly (upside down) to a female connector on your pcb, no cable needed.6) If we are to get even craftier, you can add a usb port, and a dcdc to your board, and supply the raspberry pi. One supply solution.Happy tinkering!

author: matb
author_rank: Regular Contributor
timestamp: March 09, 2022, 02:56:13 pm
content: Can you link the modules you are using.I guess where you wrote "10k pullup" means that there are I2C pull-ups ?Where is the +5V generated, on the raspberry, what is the max current ?Can you like circle sections of the schematic so that it's easier to read ?Maybe a little fuse could be a good addition.

author: matb
author_rank: Regular Contributor
timestamp: March 09, 2022, 03:02:04 pm
content: You have the symbols pins the wrong way around, it's supposed to be like this.not this

author: visoft
author_rank: Newbie
timestamp: March 11, 2022, 01:37:33 pm
content: Hi all!Thank you for the feedback!Some additional questions:1) Some breakouts have pullups some not. I made a budget, is 1.9K pullup. Is it ok? Too strong? On some chips, the lower limit is at 1K. So I guess it is fine?2) The routing of SDA and SCL is very different. Again, afaik there are no timing issues for I2C. But want to double check with you. Have no idea what is the operating frequency [Don't have how to measure it, maybe is ~400KHz]. For sure there are some software settings but until now wasn't in focus.Now some answers:@matb: I put some more love in schematic. Pdf updated in the repo:https://github.com/cristi-zz/ha-pcb/blob/master/pdfs/ha-pcb.pdf> Can you link the modules you are using?Yes, they are in the readme:https://github.com/cristi-zz/ha-pcbQuote from: matb on March 09, 2022, 02:56:13 pm+5V comes from the RaPi. Fed by its microUSB from a wall charger. I bought a UPS with 5V/2A USB but only with the Raspberry the voltage drops to 4.7-4.8V. FAIL. But that's another topic.I don't know how much current the board is drawing, I would estimate that no more than 50-100mA.I have no idea what "circle sections of the schematic " means. Isolate them somehow? Draw some border around them?Fuse, well, I already had a big pain with the BOM (I ordered first then built the schematic). Also, I don't exactly know what to put.Quote from: nvmR on March 09, 2022, 02:30:29 pmHehe, Thank you! It was needed, on actual breadboards, some wires get loose and relays start to resonate. Ugly.Added a revision number. Name . . . well, for the next one!RJs, they supposed to be vertical but the ones I bought had ZERO retention. So I moved to sth I had around. I moved them to the edge of the board now. Thanks!All breakout boards have some pins labeled on silkscreen. Will be easy to match them. Also, some put pin 1 on VCC, others on GND, others, dunno. Labeled as much as I could, just to be sure.Won't do w rounded corners. Don't know yet where I will make them.5+6 I am fan of iterative approach. Next iteration will have SMD parts, no breakout boards and maybe fancier power supply [eg feed the RaPi from some beefier 5V with UPS]. For now, I want to close the cycle sooner rather than later. Doubt that everything will go smoothly.Also, joking around, next iteration will be for "next pandemy". Or alien invasion, who knows? Disease: checked, war: checked, famine: WiP.Now I have to find a manufacturer, mount all the ancillary parts AND write a bit of software (esp testing). So no more hardware experiments are in store, for this board.Cheers to all!Feedback was a nice surprise!p.s. As an afterthought I linked 2 GPIOs to GND through a 1K resistor. I will use them to "read" what board is it from software. Esp tests. Don't want to run tests when board is in production.

author: visoft
author_rank: Newbie
timestamp: January 11, 2023, 12:01:33 pm
content: Thank you for all the help!The board is in production, a bit of sawing before, some bodge wires, but this is life! It took me few weeks to mount it but life kicked in and forgot to update the story.Now I gathered some pics and compiled a blog post:https://www.visoft.ro/beginner/expanding-the-stack-designing-a-pcb/2372/Cheers and keep up the good work!p.s. Board is 6m+ in production and no hiccups.