EAGLE schematic capture and board layout problems

Community PCB Design
1

I’m about to start the manual and then auto routing process of my schematic see the following link for my schematic but before doing this I’ve read quite a lot on different bits of advice on completing the schematic properly before embarking on any routing.

With regards to the routing I’ve read up on main aspects such as the selection of the routing grid in relation to the trace width, avoiding dimension errors and avoiding clearance errors.

Regarding my schematic I’ve got two components with each having a pin that I do not need to connect to anything at all. I’ve followed different pieces of advice and realized there is no “not connected” library in Eagle hence I created mine as per the following link. I then connect this custom symbol to my IC pin but no connection takes place and when I run my ERC check I come across the following errors in relation to both pins:

“No SUPPLY for POWER pin U1 TAB”.

“Unconnected INPUT pin IC1 ADJ”.

https://5a600546-a-62cb3a1a-s-sites.goo … edirects=1

In addition to the above problem, can anyone see any other issues with my schematic? Apart from the values of specific components which I intentionally deleted can anyone see any problem on my schematic that I might have not anticipated? Any help is appreciated.

Now moving on to the board routing (which BTW I undertook before realizing the above mentioned problem), I’ve come learn a lot in the recent days about the following things to watch out for when laying out components and subsequently undertaking the routing:

Selection of the routing grid (in relation to the trace width): I have a routing grid of10 mil and in the DRC sizes setting I have a minimum trace width of 10mil.

Selection of the trace width whilst watching out for current carrying traces.

Avoiding dimension errors.

Avoiding clearance errors.

The following link illustrates the placement of my components before I undertake manual routing and after but if need be auto routing. Just to mention in the image below I have already used the ratsnest tool.

https://5a600546-a-62cb3a1a-s-sites.goo … edirects=1

Can anyone please identify anything at all that would cause me a problem in any way? Again any help is appreciated as it would save me time and effort solving errors.

2

If you know it to be correct, select “Approve” in that same window that’s kicking out the error.

3

I then connect this custom symbol to my IC pin but no connection takes place

If this pin is the one you do not need to connect, then don’t worry about it. But if it’s a pin that you need connected but doesn’t connect, more than likely it’s because the pin is not on the same grid as the net.

I would recommend NOT using the auto-router, it blows. Manual routing is much for efficient, and you have more control, i.e., creating 45 degree corners.

There are tons of tutorials for routing in Eagle. If you need more detailed help, I suggest that you zip up the sch and brd files and attach them to a reply here so I can take a look.

4

Hi skimask,

Thanks for the reply. I read up a little bit more and saw similar advice to your and I’ve approved them.

Hi codlink,

Thanks for the reply. Here are brd and sch files zipped and uploaded: https://sites.google.com/site/bgedsadat … ects=0&d=1

Just to mention by the time I had read your latest post i.e. codlink I had already gone ahead with manually routing and then auto-routing but I have a back up of the unrouted files which is what I have zipped up and uploaded as per the above link.

I’m aware the use of the auto-router is not the best but from the screenshot in the below link could anyone see if I’m missing out on anything or where the auto-router might have messed up?

The link below is my manual and auto routing attempt: https://sites.google.com/site/bgedsadat … edirects=0

I appreciate any help.

Thanks.

5

There should be no 90 degree corners in the traces. I see some traces touching the pads of the button on the left side. That’s all can see with the low quality image. You can follow [this tutorial to export images directly from Eagle instead of ‘print screen.’ (You can skip step 7 and for step 8, just make sure to change the DPI so the resolution is above 1000px on the shortest side)

Or you just upload the routed brd file.](http://blog.microcasts.tv/2013/11/03/eagle-how-to-export-board-image)

6

Hi codlink,

Thanks for the reply. Thanks for spotting the error regarding the touching of the pads of the button on the left side. Here are my updated brd and sch files.

I’ll correct the 90 degree triangle issue in my next design.

Can you identify any other issue/potential problem?

Thanks.

7

If you run ERC on the schematic you will see several errors. The ones about VSS and VDD can be “approved”. The others are about a lack of value for the part. For example, what is the value of C9? There is a bug in the symbol for the LM335 (IC4). I noticed that inside the part’s outline that there are -2- GNDs. Thus it appeared that a 3-pin chip had 2 pins connected to GND and the 3rd one was floating, which made no sense. After I looked at the LM335 data sheet, I understood what was going on. This is not your fault but is the fault of whoever created the library part for the LM335.

Do you need to use a TO220 version of the 5 volt regulator? If you use less than 100mA on 5VDD, then you can use a TO92 package (similar to IC4) instead, or perhaps a surface mounted part. The Autorouter left traces connecting to the pads of IC1, and to the SMD pads of IC2, IC3 and IC7 at odd angles. Traces to SMD pads of chips should only be connected to the end of the pads, and not the sides or corners. This is the fault of the Autorouter and not you, but you should correct them.

HTH

8

Quick question, how

9

The ERC is a test run on the schematic screen. There is a button on the left toolbar close to the bottom. Once you see the results, dave told you what to approve so it won’t throw an error the next time you test the schematic. DO NOT APPROVE ALL OF THEM! Some errors could be critical.

You will need to run a DRC check as well. This test is done on the board screen. You will need to get the specifications from your fab house. Hopefully they will have a DRU file to download so you can load it into the DRC check. The DRC button is by the ERC button.

These tutorials are widely accessed by searching Google.

10

Hi all,

@dave: Thanks for the advice. I’m in the process of re-routing the board which I’m doing manually and I’ll take note of connecting the traces to the SMD pads of the chips to the end of the pads.

I’m also making changes based on my board house design rules.

These are:

Change 1: Using net classes I’ll change the size of the of all +5V and +3.3V carrying traces from 10mils to 24mils. I’ll manually route these traces.

Change 2: Connect +5v to pin 1 of the DA-15 connector and GND to pin 8 of the DA-15 connector. This would supply power to the EasyDAQ card. On my breadboard setup I am supplying power to the EasyDAQ card using my breadboard setup hence on the PCB this shouldn’t be an issue. I’ll manually route these traces.

Change 3: Change of LM335 temperature sensor device in schematic as custom sensor device created from LM35 (as LM335 and LM35 have the same footprint ) indicates the +5v pin as a GND pin as opposed to a +5V pin. See this link for download of the .bxl file which you will convert to the desired CAD format i.e. Eagle.

Change 4: Manually re-route majority of the traces to keep them on top layer whilst avoiding of right angle traces. This might mean fewer vias but what impact on the board (i.e. apart from making the manufacturing of the PCB cheaper)?

Change 5: Connection of resistor directly between RX/pin 18 of zigbee module to Tx/pin 17 of PIC18F2580.

Change 6: Re-positioning of the temperature sensor based on the ground plane advice.

@codlink: thanks for the reply. The errors were not critical but I get your point always check them individually.

Thanks.

11

Manually re-route majority of the traces to keep them on top layer whilst avoiding of right angle traces. This might mean fewer vias but what impact on the board

Traces will generally be shorter thus reducing trace resistances and inductance. Also possibly less important these days, but I was taught that gentle angles were less likely to have etching problems during manufacturing. Plus, I think it looks more professional and is pleasing to the eye.

(i.e. apart from making the manufacturing of the PCB cheaper)?

What board house charges you for how many angles are on a board? If your manufacturer does, you are using the wrong one.