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Double-Check My Schematic & PCB Please!

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Im working on a purpose-built Arduino knockoff, and Ive finished my schematic and PCB. Could you please look it over, and let me know if you see any obvious errors? Also, if you have any tips or constructive criticism for schem capture or PCB layout that I could (might?) benefit from, feel free! Please keep in mind that I will be etching this board myself, so Id like to keep the number of top traces to a minimum. Since most components sit flush with the board, its hard to solder to a top-side trace under a component. Also, any vias I use need to have a wire put through the hole, and soldered to the top and bottom, so Im trying to cut back on those aswell.

8871-ardschem.png

8872-ardboard.png
 
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Mr RB

Well-Known Member
They look closer to 10, maybe 8. But they could be a lot thicker that's for sure.

And the isolate could be a lot larger, there's no need to have ground plane running between every single pad of the IC, that' sjust gonna cause soldering problems etc.

I'd rotate C2 90' to position it better, and make the tracks from C1 and C2 to the IC power pins nice thick short tracks.
 
They look closer to 10, maybe 8. But they could be a lot thicker that's for sure.

And the isolate could be a lot larger, there's no need to have ground plane running between every single pad of the IC, that' sjust gonna cause soldering problems etc.

I'd rotate C2 90' to position it better, and make the tracks from C1 and C2 to the IC power pins nice thick short tracks.
They are indeed 10mil. How big should I make them? I need to keep at least part of them this thin for them to fit between the RJ45 connectors.

And Yeah I suppose youre right about the ground plane - Ive only made PCBs with a proper solder mask and silkscreen before - so I should be thinking more about solderability. How would I go about excluding the areas I dont want the plane in from the polygon? Ive tried drawing multiple polygons and naming them all GND to connect to the GND tracks but that stopped working after two polygons. It also gave me an error about an invalid polygon when I tried to draw multiple polygons in one shot.
 
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Upped the traces to 16mil each. Is the distance between the RJ45 pads fine?

Also, still waiting for an answer to my previous question about the ground plane.

8883-ardboard.png
 

3v0

Coop Build Coordinator
Forum Supporter
The bottom RJ45, two pads up from the square. That trace comes in from the left between two pads. It looks like you can route the trace up from the processor pin and come in from the right of the connector without going between pads.

On the rest of the traces that go between the RJ45 pins I would reduce the size. to .01 or 012 inches. They look tight.

3v0
 

MrDEB

Well-Known Member
Looking at the board design you need to correct

ALL the 90 degree bends. You want 45's.
trying to determine where c1 (as noted in another post) is located??
thinkng this board could be single sided. really not dofficult but not easy to home etch a 2x board.
 
C1 and C2 are power supply filter caps, so either cap on the board could be considered C1 or C2. Why do you want 45's? I read that 90's were fine for low-speed digital circuits.

How do I neck down the traces in between the pads, without changing the entire trace?
 

MrDEB

Well-Known Member
using 90s may cause a bad trace

not a good idea. I understand that the etching solution may cause a narrower trace than wanted.
Look at professional pcb no 90's
board could be designed one sided = way easier to do.
 
I have made some changes:
8886-ardboard.png


Also, you say 90's can cause a bad trace. Is this only for home-etched boards, or for boards from, say BatchPCB, aswell?
 
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MrDEB

Well-Known Member
board looks better

its just not common practice to have 90's.
are you going to home etch or send out?
for one off its much cheaper to home etch.
expresspcb has a pretty cheap service if sending out.
trying to redesign your board for one sided, no jumpers but lead spacing of caps and crystal part number would help as I only have for a 4 pin crystal
caps should maybe be polarized as its for the power supply??
 

Mr RB

Well-Known Member
Tracks look good. I would still increase the isolate value for your ground plane. Increase it a couple mil at a time and see if you can get better soldering clearance without too many orphans. And you should probably turn thermals ON.
 
Ill play with Isolate. Thanks for the tip about thermals!

DEB, Im going to etch this one myself (rather, at school) so I will have to try for fully single sided. Also, the caps are ceramics (100nF) so they arent polarized.
 

MrDEB

Well-Known Member
look at power supply schematics

everyone I have seen use polarized caps.
reason not sure.
BUT you do have your actual power supply off board so I assume its filtered well so you might get away from using polarized caps??
what weight of boards you going to use? stay away from 2 oz as undercutting of thin traces may ocure.
found using 1 oz or even the 1/2 oz boards are very quick to etch.
 

3v0

Coop Build Coordinator
Forum Supporter
If you have not discovered DRC restring yet give it a try. Using a larger restring will increase the size of the pads. You may find the ones you have on the resistors and RJ connectors are on the small side for DIY.

3v0
 
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Im not sure what the boards we use at school are, but Im pretty sure they arent 2oz. More than likely 1/2oz but possibly 1oz. Im used to seeing a 100uF cap and a 100nF (0.1uF) cap for the power supply, and since the supply is already filtered well, I didnt think the 100uF caps would be necessary.

3v0, I asked our lab teacher today to look over the printout and he thought the pad and trace sizes were alright - he makes a few PCBs every day so I felt that he was capable of judging what the system we have at school is(n't) capable of.

Also, I wasnt able to etch the board today, so I made another couple changes, and added a battery, DS1307 and DS32kHz chip to the board (instead of being attached through the "RTC" header) since these things will always be connected. Turned thermals on too. Lemme know how this one looks:

8888-ardboard.png
 
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So I definately forgot to drill a few via's.

Note to self: next time, MUCH LARGER VIAs! Sheesh, theres barely any ring to solder to! Ahwell, lesson learned.
 
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