newb having issues tracing pcb

Thread Starter

Mr.Incredible

Joined Apr 19, 2020
17
Hello, first of this is my first time trying to create a schematic and pcb. my end goal is to have a board that acts as a 8 channel "relay" using an arduino for control. Below is the schematic i have come up with and i have tested 1 circuit of it on breadboard and it works perfectly. Then next issue is multiplying that 8 times and putting that to a pcb. the whole system should be capable of around 100 amps but will likely only see half that at worst. Below is the schematic i believe to be correct and that doesn't appear to be the issue. The issue is when i want to layout the PCB the auto trace fails only gets about 40% of the connections and i have tried to move things around but to no avail. Any help would be appreciated and if needed i can provide files.

v2PCB.PNG
 

Attachments

jpanhalt

Joined Jan 18, 2008
9,435
Your "blue" lines look like airwires. Or, do you mean then as bottom traces? If the latter, it won't work. If the former, you haven't made a PCB.
 

bertus

Joined Apr 5, 2008
20,540
Hello,

The "blue" lines look like a rats nest to me.
The lines show only wich point is connected to wich point.

Bertus
 

dl324

Joined Mar 30, 2015
10,758
auto trace fails only gets about 40%
It's highly unlikely that the autorouter would be able to complete 100% of the routes in any but the very simplest of layouts. The 40% it did in your case was the easy part.

Eagle has an autorouter. I used it a couple times to see if it was any good. It was brain dead. Manually routed boards are always more aesthetically pleasing. It's an art that some never master.
 

Thread Starter

Mr.Incredible

Joined Apr 19, 2020
17
What connectors are you using? Were you aware that the resistors you're using are surface mount?

Your schematic would be easier to read if you avoided unnecessary wire jogs and scenic routes.
they are male pin headers for the arduino plugs and then barrier screw termials for the in/out for devices. It's my first time even attempting to create a schematic so i don't really know how to make it look good just kind of went for it.
 

dl324

Joined Mar 30, 2015
10,758
It's my first time even attempting to create a schematic so i don't really know how to make it look good just kind of went for it.
Were you copying some style you saw somewhere?

Here is how I would have drawn it:
clipimage.jpg
I drew one pair of MOSFETs and duplicated it.

I can't do a full board layout example for you because I'm using the freeware version of Eagle and it won't let me do more than about a 3"x4" board, but I'll work on a partial layout later.

Are you aware that your trace sizes are going to need to be around half an inch wide in 3 ounce copper to handle the design current?

EDIT: I'd draw the board something like this:
clipimage.jpg
This is the bottom layer (GND fill). The top layer is a pour of V+. I added pads for screw connections, but decided to take the connection from the tab, so overlaid the pad and tab. The thermals on the ground and V+ pads aren't thick enough and should be eliminated in favor of a solid fill.
 
Last edited:

dl324

Joined Mar 30, 2015
10,758
@Mr.Incredible

One thing I learned from people who do layout for microprocessors is that a well drawn schematic helps to create "good" layout. Any that have been in the business for decades are good at compacting layout. The ones who don't develop the knack move on to a different profession.

Note how the schematic I drew has few wire crossings and the flow is from bottom to top. That was intentional. Also note that the placement of the resistors would suggest that they'd be placed near their respective transistor and the components were placed to minimize fly wire crossings.

Your schematic was drawn willy nilly with little attention given to planning, placement, or interconnect. Ditto for your board placement.
 
Last edited:
Top