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Circuit Board Design - DIP Switches? Jumpers?

Ernest George

Jul 18, 2014
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Hi Folks!

I have a really weird question (of course!). I'm building a board, and for prototyping purposes I left 4 traces disconnected like this;

A A
B B
C C
D D

with the idea being that I could join them up later after I had determined their correct positions. For instance, it could be
A joins to C, D joins to A etc.

I'm making a new version of the circuit board but I still have this issue - I will never know ahead of time how the lines should be connected until I see the application.

I'd love to come up with a way to install a component that would allow me to hard connect each line from the first column to any line in the second column and be able to do this for all 4 connections.

Do you catch my meaning? It's kind of hard to explain. But A on the left might go to anywhere from A to D on the right. Same thing with B, C, & D - each one of those circuits could go to any position on the right.

Would a DIP switch do that or do you know of any way to accomplish this from a hardware perspective? Feel free to ask for further clarity if needed!
 

Gryd3

Jun 25, 2014
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Hi Folks!

I have a really weird question (of course!). I'm building a board, and for prototyping purposes I left 4 traces disconnected like this;

A A
B B
C C
D D

with the idea being that I could join them up later after I had determined their correct positions. For instance, it could be
A joins to C, D joins to A etc.

I'm making a new version of the circuit board but I still have this issue - I will never know ahead of time how the lines should be connected until I see the application.

I'd love to come up with a way to install a component that would allow me to hard connect each line from the first column to any line in the second column and be able to do this for all 4 connections.

Do you catch my meaning? It's kind of hard to explain. But A on the left might go to anywhere from A to D on the right. Same thing with B, C, & D - each one of those circuits could go to any position on the right.

Would a DIP switch do that or do you know of any way to accomplish this from a hardware perspective? Feel free to ask for further clarity if needed!
I think dip switches or jumpers would make this kind of complicated... possible, but complicated.
Considering there would be numerous cases for the traces to overlap requiring jumpers or numerous dip switch rows.
What is the purpose of those 4 lines?
If they are to be connected to an external source, it may be worth while to print labels on the enclosure and use a terminal block to connect the wires to in the required order.
 

Ernest George

Jul 18, 2014
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Terminal blocks is a good idea but it's not really possible in this particular configuration (at least, in it's current design). I was hoping that there would be a way to do it on the circuit board through switches or something. I have little experience with circuit board design which is why I was hoping someone would say, 'oh sure, use one of these' - hahahaha :)

I've attached a pic of the two sides of the traces that would need to be joined. For prototyping purposes I just solder jumper wires between them, which is OK, but for production this would not work. In the real-world different applications will require connections between them to vary.
 

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KrisBlueNZ

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What comes to mind is a grid formed by four tracks on one side of the board, and another four track at a 90° angle on the other side, with some way to interconnect them. Here's my first thought; you can probably improve on it.

grid interconnect idea.png

The blue tracks (underside) are A~D from the driving device(s), and the red tracks (top side) are A~D to the receiving device(s). The round bits are just vias, and I've included a square copper fill on the top side with a void in the solder mask. There's also a void in the solder mask on each of the red tracks where they pass a via.

So you would just put solder blobs between vias and tracks, all on the top side, to choose what connects to what. You might have to experiment with the sizes of the voids in the solder mask to prevent accidental shorts, depending on how you get the board assembled.

That's just a general idea.

Edit: You only need three columns of vias because each via can be soldered to a track on either side. Actually you don't even need the middle column of vias.
 

Ernest George

Jul 18, 2014
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That's an interesting design Kris - thank you for posting it!

It still pre-supposes different manufacturing options according to customer needs. What I was hoping for was something like DIP switches so that every board could be stamped out the same and then you customize the switches accordingly depending on application.

Ultimately, the wires are connected to an external harness by means of a connection block. So, in theory, I could run the lines straight across, label them on the outside, and have them end in bullet connectors so the end user can mix 'n match them at will as Gryd3 mentioned. This might end up being the best way - more thought will be required!
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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It also depends on how configurable you want it to be.

You could use a 4x2 pin female header and push links into them. Alternately you could use an 8 pin IC socket and make up a small daughter board with 8 pins and wire the connections onto it. This could then be plugged in. These solutions are good if you want to be able to field-program it without soldering to the board.

The pluggable option is better for less skilled operators (maybe end users). You could even go to the effort of using a ZIF socket. If you used a 16 pin socket you could provide 2 configurations by turning the plug around, or have it encoded so that it works the same way no matter the orientation (A true "dummies" solution).

Kris' solder jumper solution is a good one for a more permanent solution.

Another option would be to have 4 small PCB mounted rotary switches you could turn to connect each individual input to A, B, C, or D. This would not prevent you connecting more than one together and may be the most expensive option. This would be, in effect, similar to having 16 individual DIP switches, although that would allow you to do even more wrong.

However, your solution of labelling the wires and then connecting them to the correct points on the board sounds even better.
 

KrisBlueNZ

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A 4x2 header won't work with simple jumper shunts. Here's maybe the simplest option if you want to use jumper shunts.

grid idea 2.png

As before, the blue tracks (underside) are the incoming signals, and the red track at the top are the outgoing signals. Every circle is a pin, and they're spaced at 0.1" pitch in each dimension. You use four standard 0.1" jumper shunts to connect each blue signal to the appropriate red signal. The jumper shunts are placed horizontally, between columns 1-2, 2-3, 4-5 or 5-6 as necessary.

Edit: clearer diagram
 
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Ernest George

Jul 18, 2014
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A 4x2 header won't work with simple jumper shunts. Here's maybe the simplest option if you want to use jumper shunts.

View attachment 17441

As before, the blue tracks (underside) are the incoming signals, and the red track at the top are the outgoing signals. Every circle is a pin, and they're spaced at 0.1" pitch in each dimension. You use four standard 0.1" jumper shunts to connect each blue signal to the appropriate red signal. The jumper shunts are placed horizontally, between columns 1-2, 2-3, 4-5 or 5-6 as necessary.

Edit: clearer diagram


Wow - this looks like it might just be the answer! Did you get new CAD software? If so, good on ya!
 

KrisBlueNZ

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Wow - this looks like it might just be the answer! Did you get new CAD software? If so, good on ya!
No, it's very old CAD software!

Also, you could put a small gap e.g. 25 or 50 thou between the first three columns and the second three columns to make it impossible to put jumpers between columns 2 and 3.
 

dablakh0l

Sep 19, 2014
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I have done just what Kris showed on a board I had designed, however I did it with vias and solderable spaces, so that you didn't even have to use wire, just a small solder dot would join the tracks. If cost is a concern for large scale production, I often use 0-ohm resistors for these types of locked junctions.

Your mileage may vary.
 
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