How to neatly attach wires to four SF 4x4 buttonpads?

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How to neatly attach wires to four SF 4x4 buttonpads?

Postby bitbutter » Mon Jun 16, 2008 7:44 am

Hello, i'm pretty new to electronics and I'm trying to figure out the neatest way to wire up the four sparkfun 4x4 button pad pcbs that i have for a monome clone project.

I saw this image on flickr which looks like a smart solution
http://www.flickr.com/photos/unsped/2320709948/sizes/o/

But i'm having a hard time seeing exactly how the wires have been attached to the vias here. Can anyone see how this has been done? are there pins being used somehow?, how does this approach deal with attaching several wires to one via? Are there specific names for connectors/sockets etc i should look up to help with realising something like this?

(i mailed the guy who created the image, but have had no reply yet, so i'm casting about for other insights)

Thanks in advance!
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Re: How to neatly attach wires to four SF 4x4 buttonpads?

Postby bigglez » Mon Jun 16, 2008 10:44 am

Greetings (No First name Supplied),
bitbutter wrote:But i'm having a hard time seeing exactly how the wires have been attached to the vias here. Can anyone see how this has been done? are there pins being used somehow?, how does this approach deal with attaching several wires to one via? Are there specific names for connectors/sockets etc i should look up to help with realising something like this?


In that PIX the flexible wires are anchored to the PCB
with headers (not sure of the brand or type). The PCB
has four identical sections, and could be singulated in
to four identical boards, so there are connectors near
the centre of the PCB that would be on the edge of
idividual boards. There are insulated wire "busses"
from the centre to the edge in this PIX, but you can
place the mating connectors near the PCB middle and
skip the buss wiring altogether.

The pads and holes on the bare PCB are designed to
accept standard headers, allowing the flexible wires to
be removed for installation and servicing.

It would be easy to solder the flexible wires directly
to those pads, but you'd loose the freedom to unplug.

Typical headers in 100mil (0.1inch) pitch can be
found at most supply houses. For example,
KK4030 by Molex. The mating female shells are these.

There's a wide range of styles and vendors - take a
look on line in the supplier's catalog for options. Usually,
the female contacts are sold separately.

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Postby bitbutter » Mon Jun 16, 2008 11:29 am

Thanks, your reply is very informative.

There's one thing i'm still unsure about. In the photograph, there are places where more than one flexible wire is connected to a single via. This is necessary to extend electrical signals from the 'first' pcb to the other (identical) three.

This is particularly noticeable with the connections on the right hand edge of the four pcbs in the photo.

Does some kind of stackable header(connector?) for flexible wires exist?, or have multiple flexible wires just been soldered directly to the same pin here somehow?
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Postby bigglez » Mon Jun 16, 2008 12:07 pm

Greetings (Still No First Name Supplied),
bitbutter wrote:There's one thing i'm still unsure about. In the photograph, there are places where more than one flexible wire is connected to a single via. This is necessary to extend electrical signals from the 'first' pcb to the other (identical) three.

A lot depends upon your final design goal. Are you copying
this design? If so, the author of the PIX should help
you instead of us guessing.

bitbutter wrote:Does some kind of stackable header(connector?) for flexible wires exist?, or have multiple flexible wires just been soldered directly to the same pin here somehow?

Therre are stacking connectors, but probably not what
you require. Take a look at the on-line catalogs from
Digi-key or Mouser.

With care two (possibly three) small flexible wires
can be crimped or soldered into the female contacts.
Looking at the PIX again I don't think there are two
connectors, instead the wires are soldered to the
posts (male headers).

Without a schematic it would be hard to determine
whether multiple wires are required. The easy way
to drive the group of four would be with four times
the circuitry for one PCB. Trying to extend the MUX
scheme to drive 64 LEDs would probably require
stronger drivers.

What is your first name?

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Postby bitbutter » Tue Jun 17, 2008 5:59 am

re. my name: Sorry, I know it might not look very friendly but i'd like to remain as anonymous as possible.

I would be very interested to speak with the person who built this project, but so far that hasn't been possible. I think I would like to copy this design, but to be sure, i'm trying to understand how it has been built.

Looking at the PIX again I don't think there are two
connectors, instead the wires are soldered to the
posts (male headers).


I see. This would work for me too. Do you know if there's a 'best practice' way to solder wires to posts in this way? my googling around so far hasn't turned up any guides, or photos.

Thanks again for your help!
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Postby bigglez » Tue Jun 17, 2008 10:49 am

bitbutter wrote:re. my name: Sorry, I know it might not look very friendly but i'd like to remain as anonymous as possible.


Sure, I understand. Good luck with your project!
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Postby unsped » Tue Jun 17, 2008 3:30 pm

http://www.flickr.com/photos/unsped/2260394671/sizes/o/

please don't pay any attention to the connections off the board as they are not correct, but this shows you how i hooked the boards up.

i used solid core wire and bent the ends at right angles then poked them through the holes in the pcb where the headers would be.

for the ends where 2 wires into one via ... i wonder if i can explain this well.

i used standard .1" headers, and soldered them in, then i soldered all the wires to this header, the solid header gave me an easy to solder point, it can get a little tight. i think put liquid plumbers tape over these connections to prevent any future shorting.

i would take better pictures but i no longer have this prototype. and if i had to do it again i probably wouldn't use headers again, i would just feed one wire through the via (so i dont have to worry about traces ripping and solder it and build up a nice pad, then solder the thinner braided wire to the pad.
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Postby bitbutter » Thu Jun 19, 2008 12:03 pm

Hi unsped. Thanks very much for the clarification, that makes sense.

I already have the diagram you posted, it's been a very helpful aid--as have all your other photos too.

While you're here, do you ave the arduino code that you used, on your computer, and if so would you mind sharing it?
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Postby unsped » Wed Jun 25, 2008 10:54 am

you may actually want to look at this site:

http://bricktable.wordpress.com

they did a rewrite of the code, i havent tested it but its potentially alot more stable. although it is 40h and not 64, however that shouldn't matter much.
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Postby bitbutter » Wed Jun 25, 2008 11:29 am

Thanks. I've been following the bricktable project too, good to know it gets your endorsement :) (i'm hoping the group buy plan for you pcb design goes ahead too)
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