Advice on first PCB design

Thread Starter

gautam023

Joined Apr 26, 2021
11
Hello Everyone,
I am looking for any advice on my first PCB design. The function of the board is to monitor a battery pack and send the data to a smartphone via BLE.
It also includes a power supply for Arduino and other sensors. I am using LT3958 in the SEPIC configuration for this. I used 20mil for the main power input from the 72V battery pack, and 5V line since I will be using that to charge the smartphone later. And the rest is 6 mil. Should I be using different trace widths for power and signal lines? The current requirements are not that high for +15V and -15V lines.
 

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jiggermole

Joined Jul 29, 2016
4
i usually use an online trace width calculator using my expected worst case scenario of current draw. That's worked well for me so far, as in I haven't blown off a trace yet. I use 6mil for signal lines and 8mil minimum for anything with a current draw. Board houses will have a limitation page on what they can or cannot do. Some like oshpark have a design rule check file that is bundled right with eagle so eagle can do the checking for you.
 

Thread Starter

gautam023

Joined Apr 26, 2021
11
i usually use an online trace width calculator using my expected worst case scenario of current draw. That's worked well for me so far, as in I haven't blown off a trace yet. I use 6mil for signal lines and 8mil minimum for anything with a current draw. Board houses will have a limitation page on what they can or cannot do. Some like oshpark have a design rule check file that is bundled right with eagle so eagle can do the checking for you.
Eagle's default DRC gave no errors. I also went and check trace widths for particular current from the Trace calculator. The width of my traces is higher than what is shown from that calculator. I also checked voltage drop due to widths I used and the drop was within acceptable range
 

jiggermole

Joined Jul 29, 2016
4
BasicPCB is a decent barebones fab house, no real customization, but its cheap and relatively quick.
Oshpark is one that is my current go to. They display the board how its going to be made when you upload so in theory you can see if you messed up. But you get purple pcbs only. I think maybe black.
I've also used seeed studio for boards too. A LOT of customization here, maybe too much. 1oz to 4oz pours, the whole nine yards.

I don't really see any glaring issues in your schematic, though I haven't spent hours working on it like you. The board not being a rectangle may cost you a decent deal more from the fab house. Maybe make it a rectangle with no pours on the cut out area, and cut it out yourself with a bandsaw or something to get it cheaper. I've done this on a board or two. I put a drill hole to mark out where I need to cut. The fab house will gladly put drill holes, but a notch out like what you have will cost more.

And for the DRC I just saw the two wire stub warnings and you already approved the four clearance ones.

Cam processor, load job file, system examples, third party, oshpark 2 layer. Ran it and tried it on oshpark and it failed. it looks like your board outline was broken, thats why it appeared black inside and outside your board in eagle. i redrew it and it passed. If I remember to I should have attached the saved file. You could upload it to oshpark with and without the cutout and see if it will cost you extra with the notch or not.

I over engineer my stuff most of the time but I always expect it to blow up. If it does, you know exactly what trace was too small. Last thing I would go over, is to make sure you can solder the stuff down. Giving yourself enough room around components if you're hand soldering it. If you're going to reflow it, oshpark can make a stencil from your board files. Pololu also does stencils.
 

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Dave Lowther

Joined Sep 8, 2016
57
BasicPCB is a decent barebones fab house, no real customization, but its cheap and relatively quick.
Oshpark is one that is my current go to. They display the board how its going to be made when you upload so in theory you can see if you messed up.
Depending on where the OP lives it might be quicker and cheaper to get a PCB made in China. I live in the UK and the one time I used Oshpark the shipping time was very long, about 6 weeks. I always use PCBWay now. I've had > 10 different PCBs made by them with no problems. They also show an image of the board that will be made. The basic cost for small (not sure of the size limit) PCBs is $5 for 5 off (min quantity is 5). Depnding on how patient one is, the shipping costs can be very low too. I go for the 'PCBWay express' shipping which is not the cheapest option but gives about a 2 week shipping time.
 

Thread Starter

gautam023

Joined Apr 26, 2021
11
BasicPCB is a decent barebones fab house, no real customization, but its cheap and relatively quick.
Oshpark is one that is my current go to. They display the board how its going to be made when you upload so in theory you can see if you messed up. But you get purple pcbs only. I think maybe black.
I've also used seeed studio for boards too. A LOT of customization here, maybe too much. 1oz to 4oz pours, the whole nine yards.

I don't really see any glaring issues in your schematic, though I haven't spent hours working on it like you. The board not being a rectangle may cost you a decent deal more from the fab house. Maybe make it a rectangle with no pours on the cut out area, and cut it out yourself with a bandsaw or something to get it cheaper. I've done this on a board or two. I put a drill hole to mark out where I need to cut. The fab house will gladly put drill holes, but a notch out like what you have will cost more.

And for the DRC I just saw the two wire stub warnings and you already approved the four clearance ones.

Cam processor, load job file, system examples, third party, oshpark 2 layer. Ran it and tried it on oshpark and it failed. it looks like your board outline was broken, thats why it appeared black inside and outside your board in eagle. i redrew it and it passed. If I remember to I should have attached the saved file. You could upload it to oshpark with and without the cutout and see if it will cost you extra with the notch or not.

I over engineer my stuff most of the time but I always expect it to blow up. If it does, you know exactly what trace was too small. Last thing I would go over, is to make sure you can solder the stuff down. Giving yourself enough room around components if you're hand soldering it. If you're going to reflow it, oshpark can make a stencil from your board files. Pololu also does stencils.
Thank you for your advice. (The clearance was from some components internals over which I have no control.)
 

Thread Starter

gautam023

Joined Apr 26, 2021
11
Depending on where the OP lives it might be quicker and cheaper to get a PCB made in China. I live in the UK and the one time I used Oshpark the shipping time was very long, about 6 weeks. I always use PCBWay now. I've had > 10 different PCBs made by them with no problems. They also show an image of the board that will be made. The basic cost for small (not sure of the size limit) PCBs is $5 for 5 off (min quantity is 5). Depnding on how patient one is, the shipping costs can be very low too. I go for the 'PCBWay express' shipping which is not the cheapest option but gives about a 2 week shipping time.
Thank you. I am in Italy. Based on your experience think I will check out PCBWay first.
 

Irving

Joined Jan 30, 2016
1,496
Also look at jlcpcb.com; USD2 for 5 pcb (100mm x 100mm, FR4, 2-side 1oz copper) + USD7 for stencil + USD20 7-10 shipping (Fedex) to Italy = USD29. Currently offering free SMT assembly as long as parts are selected from their online catalog.

I've used their assembly service a couple of times, including leaving off a TSSOP-30 chip I later hand-soldered as it wasn't in their catalog (they did quote but the cost of the 5-off parts plus special handling was silly money for a 4GBP part!).

PCBWay currently USD5 + USD10 for stencil + USD19 shipping (Fedex) = USD34, or USD5 + USD10 + USD30 assembly = USD45 (shipping is free with assembly, parts from their stock).

Can't comment on relative cost of parts from each, but jlcpcb were keenly priced.
 

nerdegutta

Joined Dec 15, 2009
2,681
I second JLCPCB. Besides all the options and choices you have, you're also able to see the different processes your board is going through. Last time I use JLCPCB, I got an extra puzzle:
Screenshot_20210608-065806_Instagram.jpg

The puzzle was not mission critical, but I thought it was fun...
 

Ian0

Joined Aug 7, 2020
2,192
I'll put in a good word for Allpcb. They check things manually before they make them, and ask questions you can understand!
 
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