Quadcopter flight control board routing

Question

I am in the process of redesigning my quadcopter flight control board from running brushed to brushless motors . This necessitated me adding a 5v buck boost regulator and some other minor changes as well as completely relocating or re-orientating virtually every component on the board. As you can no doubt tell from my board layout I am a novice when it comes to PCB routing but I have done the best that I can so far. The circuit is proven so it is just a matter of finalising the routing so I can get some test PCB's made and build them out at home which I am completely comfortable and experienced at doing. Even with the first successful brushed version of this board the Iteadstudio DRC would flag clearance errors on the Atmega, MPU6050, and Molex connectors and this has not proved to be an issue as I have made around twenty of these boards with no issues and they perform flawlessly. With this in mind I am wary of believing some clearance issues being flagged by the DRC on this board but would just like someone to cast an eye over what I have done and point out any glaringly obvious omissions or mistakes that may stop the board from functioning from what they can see. Being a novice I realise that a seasoned professional would make a much more elegant job of the routing but I am not after perfection or anything close to it, just something that will work and that I can hand assemble. When I run rats nest I can see a lot of un-routed airwires but if I run a "run length ulp" it only shows two un-routed wires. I have not checked through all the clearance errors but as I said the only ones that I would be concerned with are trace to trace and/or via clearances. Thank you for any help or advice of a constructive nature and thanks for your time, Pedro 
 Attachments: Final _Gyro Oriented same as AF CN.zip

autodeskguest · Accepted Answer

On 19.10.2016 05:15, Peter Newman wrote: Thanks for your advice and suggestions Morten, I appreciate your time. The battery and USB powering is used only during fIrmware and bootloader flashing. Thanks for the suggestion on the adjustable buck boost I'll look into that but these are only limited production runs done at home. The logic level output is only used as a signal into the Electronic Speed Controller for each motor and the motor is independently powered from another battery. Regarding your suggestions on adjusting my min clearance settings in the DRU check, I am not certain of exactly where to adjust those settings but I assume it may be in Edit > Net Classes? Any chance that you could be more specific as there are quite a few different places to adjust things in all those tabs. Thanks again you have been a big help. Yes, you are right regarding the location of the net classes edit. (The general clearance stettings are under a tab in the DRC settings box). In the net classes box, you will find the last "clearance" column for class 0 set to 10mil. Set it to 0, and for class1 and class2, set it to 8. Now rerun a DRC. The clearance errors that are left can be fixed by modifying the routing slightly. But as I mentioned, first fix the airwire issues. Read the lower left status message after a ratsnest is done. It will tell you how many airwires are left. Unfortunately Eagle doesn't report those in the DRC issue list, although it has been a topic on the suggest forum for a while.

autodeskguest · Answer

On 17.10.2016 12:42, Peter Newman wrote:

I am in the process of redesigning my quadcopter flight control board from running brushed to brushless motors . This necessitated me adding a 5v buck boost regulator and some other minor changes as well as completely relocating or re-orientating virtually every component on the board. As you can no doubt tell from my board layout I am a novice when it comes to PCB routing but I have done the best that I can so far. The circuit is proven so it is just a matter of finalising the routing so I can get some test PCB's made and build them out at home which I am completely comfortable and experienced at doing.

Even with the first successful brushed version of this board the Iteadstudio DRC would flag clearance errors on the Atmega, MPU6050, and Molex connectors and this has not proved to be an issue as I have made around twenty of these boards with no issues and they perform flawlessly.

With this in mind I am wary of believing some clearance issues being flagged by the DRC on this board but would just like someone to cast an eye over what I have done and point out any glaringly obvious omissions or mistakes that may stop the board from functioning from what they can see. Being a novice I realise that a seasoned professional would make a much more elegant job of the routing but I am not after perfection or anything close to it, just something that will work and that I can hand assemble. When I run rats nest I can see a lot of un-routed airwires but if I run a "run length ulp" it only shows two un-routed wires. I have not checked through all the clearance errors but as I said the only ones that I would be concerned with are trace to trace and/or via clearances.

Thank you for any help or advice of a constructive nature and thanks for your time,
Pedro

-The schematic is missing, so I can't look at the circuits or even

identify the components functions, wich is somewhat important for

layout, especially when it comes to smps regulators.

-When I do ratsnest, there are 26 serious airwires left. Maybe you need

to add gnd vias around here and ther?

-A quick look at clearances tell me these are probably fine.

-A quick look at the +5v net suggests that you have been sloppy with

decoupling capacitors. Since this board contains a xyz sensor, I'd be

careful with power- and ambient noise. A smps reg just next to it may

have undesired effects.

If I were you, I would add another two layers (dedicated gnd and

+5v/vcc) and get this manufactured in China at very low cost.

autodeskguest · Answer

On 17.10.2016 21:08, Peter Newman wrote: For some reason I could not attach the schematic as well as the board file in my initial post, presumably because of size restrictions so I am now doing so Thanks Some comments on the schematics (yea, I know you said the circuit is proven, but still): -I am not sure if you can plug the battery direct to USB like that. That is outside my knowledge, and I would have to check it out. Maybe the battery type allows this, or maybe you dont care if its overcharged, and maybe it doesn't matter if it catches fire during charging -For easier BOM management and to optimize volume pricing, I'd consider replacing the U3 (TPS63001) and U$3 (TPS63002?) with the same adjustable output voltage chip (TPS63000). (For tidyness, you may want to rename U$3) - How are the brushless motors driven, and what current do they need? Driving with a logic output sounds harsh. If the motors have a speed control input, at least I would assume you need some direct voltage. And, I would also expect some reverse voltage protection diode over the motor drive. Back to the layout -Make the VCC track routing wider. Make sure there is a thick wire from the battery to the regulators. Also make sure the gnd wire/fill is just as thick. The other power tracks could do with some improving too. Some tracks take totally wild directions, like 5v below u$3. -You default class 0 clearance has been set to 10. Set it to 0 and use general 6mm clearance rule. Also, the 10mil clearance set on the vcc and gnd is impossible to meet because of pad sizes and placement. Get rid of them, or set them to min (8mil seems to do). The clearances left now can be resolved by fine tuning. -There is an excess of layer crossings. You can optimize that if you want. -Personally I prefer to route stuff to grid and 45deg angles. That helps me keep tidyness and I know if I see something off, I know something was moved and needs some cleanup. I see yours is a bit messy, although it will work if the DRC and airwire issues are cleared. -Check the position of the xyz sensor. If its in a quadcopter, I would assume the ideal position would be at the center of the copter, but maybe that can be offset in software? Or maybe the pcb is slightly offset on the copter itself? In any case, make sure its far away from noisy components (maybe there is a note about that in the datasheet?) L2 looks a bit threatening. -And, like last time, check the need for decoupling caps. Before you go on fixing the routing, I suggest you fix the airwires. To fix them you need to add several vias, and they may need you to move stuff around, creating new clearance issues.

Quadcopter flight control board routing

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