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mystery air wire in my project [message #171558] Tue, 05 September 2017 09:16 Go to next message
Eric Chapin
Messages: 4
Registered: June 2017
Junior Member
https://www.dropbox.com/s/p0y0s7xhj8qqhb7/LED%20cube%20board.brd?dl=0 my current WIP at this point.

Can anyone explain the air wire between GND and VCC near the bottom?  Picture: https://imgur.com/on0AMd8 the pink arrow.  There's also a few yellow X's where the trace connects with decoupling capacitor pins, like Eagle doesn't know those traces are connected with capacitor's leg.

I don't have the schematic for this one, I got the original one from https://www.oshpark.com/shared_projects/LyWFDL0A There was some mistakes with the original board, some grounds rails weren't connected, and the decoupling capacitor was in series between VCC rail and the chip's VCC pin, this would have isolated and prevented all 9 chips from getting power. I changed the caps so all VCC pins were connected directly to VCC rail, and the capacitor now connects from VCC to ground. Also fixed a couple missing ground connections to the 16 transistors and to ground pin of one of the chip.  It's almost like the previous person designed the board without using Eagle's schematic for some reason?  Oh and I added text of pin function with the 2 pin headers, marked all 9 chips, and noted all resistor (except one marked 330) and all capacitors are the same value 100 and 0.1uF

Anyway can someone double check that I don't have VCC and ground crossed and see why there's air wire trying to connect that 2?  It'd be around $60 down the drain if the board was useless because I missed something.

Still to do: replace 16 pin header with 12 as 4 of the pins aren't used and one pin (15) is in the way of the circuit trace.

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Re: mystery air wire in my project [message #171559 is a reply to message #171558] Tue, 05 September 2017 10:45 Go to previous messageGo to next message
Morten Leikvoll
Messages: 1351
Registered: November 2007
Senior Member
On 05.09.2017 11:16, Eric Chapin wrote:
> https://www.dropbox.com/s/p0y0s7xhj8qqhb7/LED%20cube%20board.brd?dl=0 my current WIP at this point.
>
> Can anyone explain the air wire between GND and VCC near the bottom?  Picture: https://imgur.com/on0AMd8 the pink arrow.  There's also a few yellow X's where the trace connects with decoupling capacitor pins, like Eagle doesn't know those traces are connected with capacitor's leg.
>
> I don't have the schematic for this one, I got the original one from https://www.oshpark.com/shared_projects/LyWFDL0A There was some mistakes with the original board, some grounds rails weren't connected, and the decoupling capacitor was in series between VCC rail and the chip's VCC pin, this would have isolated and prevented all 9 chips from getting power. I changed the caps so all VCC pins were connected directly to VCC rail, and the capacitor now connects from VCC to ground. Also fixed a couple missing ground connections to the 16 transistors and to ground pin of one of the chip.  It's almost like the previous person designed the board without using Eagle's schematic for some reason?  Oh and I added text of pin function with the 2 pin headers, marked all 9 chips, and noted all resistor (except one marked 330) and all capacitors are the same value 100 and 0.1uF
>
> Anyway can someone double check that I don't have VCC and ground crossed and see why there's air wire trying to connect that 2?  It'd be around $60 down the drain if the board was useless because I missed something.
>
> Still to do: replace 16 pin header with 12 as 4 of the pins aren't used and one pin (15) is in the way of the circuit trace.

The VIA there is logically connected to that blue net, and I think it is
not connected to the overlapping. Yellow cross means there is an
vertical airwire between layers.

Use show on the nets or vias and you will see the whole net highlighted,
and maybe find connections that shouldnt be there.

Also remember (BEFORE MANUFACTURING!) to do DRC and assert # of
airwires=0 after ratsnest.
Re: mystery air wire in my project [message #171566 is a reply to message #171558] Tue, 05 September 2017 17:56 Go to previous messageGo to next message
Rob Pearce
Messages: 484
Registered: September 2012
Senior Member
On 05/09/17 10:16, Eric Chapin wrote:
> Can anyone explain the air wire between GND and VCC near the bottom? Picture: https://imgur.com/on0AMd8 the pink arrow. There's also a few yellow X's where the trace connects with decoupling capacitor pins, like Eagle doesn't know those traces are connected with capacitor's leg.


As Morten said, that via is associated with the upper trace net, not the
one it's placed over. If you move the via you should see that the
airwire follows it, whereas if you move the lower diagonal trace (and
the unconnected end of the horizontal bit it doesn't connect to) the
airwire will stay still.
Re: mystery air wire in my project [message #171569 is a reply to message #171559] Tue, 05 September 2017 19:35 Go to previous messageGo to next message
Eric Chapin
Messages: 4
Registered: June 2017
Junior Member
> CadSoft Guest wrote:
>
> The VIA there is logically connected to that blue net, and I think it is
> not connected to the overlapping. Yellow cross means there is an
> vertical airwire between layers.
>
> Use show on the nets or vias and you will see the whole net highlighted,
> and maybe find connections that shouldnt be there.
>

Using show, I noticed that the 2 vias for the power connector were both connected to VCC rail when one should be GND, that explains the air wire. Now to fix the yellow X's and check for sneaky air wires

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Re: mystery air wire in my project [message #171570 is a reply to message #171566] Tue, 05 September 2017 19:56 Go to previous message
Eric Chapin
Messages: 4
Registered: June 2017
Junior Member
Yes I got it thank you.  I did manage to find one more sneaky airwire by typing in command "display none unrouted" which hid everything but unrouted.  All other unrouted are tiny and within the hole for component leg so it'd be connected when it's soldered in place.

Checked top layer only for crossed lines, then checked bottom layer for crossed lines.   And finally ran error to find any more issue. Nearly all reported clearance issue with trace at vias and pads but those should be OK since they are supposed to be connected.  I didn't find any trace touching pad or vias where they aren't supposed to be.

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