First attempt at PCB design - Page 1
Forum section: electronics / projects

author: Skutov
author_rank: Newbie
timestamp: September 11, 2014, 03:02:57 pm
content: Hi there,I've been a follower of Dave for some time. I'm a programmer by trade but my job has recently required me to develop the hardware for a project that I'm working on. The project is an environmental monitoring solution that is meant to be a deploy and forget device that can be placed inside a building for 6 months upwards to collect data and stream it to a database server. I have been developing the project using the Arduino platform as the hardware designs for most of their boards are open source, meaning I can copy and paste parts that I need without having to design them myself.Today I made my first attempt at designing a PCB in CAD, I used Eagle as I've heard some good things about them and don't know enough to disagree, the project files areup here. If people could take a look and point out any glaring errors/improvements/laugh at how terrible it is then please do, I'm hoping that I'll be bale to have a prototype of the board made in a couple of weeks so any help with making sure it won't release the magical blue smoke would be much appreciated.Thanks,// Skutov

author: Dongulus
author_rank: Regular Contributor
timestamp: September 11, 2014, 03:37:15 pm
content: People on the forums are always willing to give advice on the designs of others, but it helps to make it very easy on others to view the design. I suggest exporting your schematic and layout files to a PDF or, at the very least, take a screen captures and save them as images that can be easily viewed within your post.

author: Wilksey
author_rank: Super Contributor
timestamp: September 11, 2014, 04:21:07 pm
content: Hi,Where to begin....First of all, you don't appear to have any pull ups on your I2C bus.I can see you have copied (almost identically) the GSM arduino shield that uses the Quectel M10, unfortunately you haven't quite copied it correctly as the VBAT pins on the M10 are not connected!As for the PCB, it looks autorouted and a bit squiggly, functionally though, I would check your power track widths can take the peak current burst for your M10 module (nominally 2A).I only looked briefly at the files though, but those are my immediate thoughts.HTH!

author: Skutov
author_rank: Newbie
timestamp: September 11, 2014, 07:17:58 pm
content: Quote from: Dongulus on September 11, 2014, 03:37:15 pmGood point, here are PDF's with the changes Wilksey suggested.Board LayoutSchematicBlock DiagramQuote from: Wilksey on September 11, 2014, 04:21:07 pmThe ATMEL 2560 has internal pullups AFAIK.QuoteCorrect, that was something I deleted before I actually realised how nets work in Eagle (did I mention this was my first time ever designing a PCB?)QuoteAstute observation, indeed it is autorouted, I didn't really have any idea where to start so I tried to place the parts logically and let the autorouter take care of it, now that I actually have a working design I can fall back to I'm going to try and improve it. Also you raise a good point about the power tracks, I have widened some of them and I will check over the original shield design so I can see what they used.QuoteMuch appreciated, you've given me some things to think about tomorrow.// Skutov

author: marshallh
author_rank: Unknown
timestamp: September 11, 2014, 08:06:36 pm
content: Not bad for a first attempt. But i'll be honest, the layout is crap. Luckily you will only get better.Developing a sense of layout and part placement just takes practice.The process goes like this:1. Separate design into functional units2. While drawing the schematic keep in mind how it will be routed on the pcb.3. Group together parts in the same unit on the PCB, and place/orient them so that they can be routed efficiently4. Route5. Erase your routes, move parts again, and route againAfter a few tens of PCBs you will be able to layout the parts directly where they should go the first time. Hand routing in eagle is terrible, so check out Freerouting to assist with that (its very good for hand routing)Your U1 pads are extremely small. Instead of making footprint off the part's mechanical drawing, refer to the suggested footprint, or compensate by making things larger.

author: Skutov
author_rank: Newbie
timestamp: September 12, 2014, 01:08:47 pm
content: Quote from: marshallh on September 11, 2014, 08:06:36 pmThanks for the advice, I'll give freerouter a go. In the mean time I've tried to tidy up some of the auto-routed bits and make it a bit neater, here's thelatest version.// Skutov