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Jon's Imaginarium – Sparkfun Lock Footprints for PCB Design

Visitor

Well-Known Member
I posted about "lock" footprints in the thread the other day, but this is too important to be buried in a thread if you design your own circuit boards.

When soldering male header pins to a printed circuit board, it can be difficult to get the connector perpendicular to the board. All too often, when you look at the header after soldering, it's at an angle. Trying to square it up results in burned fingers and cuss words, but little change in the final result.

A clever guy named Pete Lewis at Sparkfun came up with a simple way to solve this problem. Alternating pads for a header connector are placed just a bit above the connector centerline and below the centerline., providing a slight interference fit (depending on hole plating) and keeping the connector perpendicular to the board when you insert it. Getting perfect connector alignment is simple with this small change in the PCB footprint. The illustration below shows the small offset from the connector centerline. The horizontal white line is the connector centerline.

Lock Footprints.jpg


The (sometimes) interference fit has a great side effect. Using this footprint for ICSP programming allows you to "plug in" a header connector if you'll only be programming the board a few time.

If you use EasyEDA, please feel free to use my library of lock connector footprints. For headers and Molex KK connectors, I've created patterns for 3 pins up to many. You should be able to find them under owner "jonchandler". I have modified my footprints from those supplied by Sparkfun - Sparkfun footprint origin at pin 1; I put the origin at the center of the pad group (as God intended). When you rotate my footprints, they stay centered in the same place on the board.

Sneaky Footprints - SparkFun Electronics
 

Visitor

Well-Known Member
Hey Mike,

I'll get you the exact file name when I get home.

Search for footprints in the user-provided libraries on the far right side of the screen. I think you can search by user name, but I didn't see how to do it during a quick look earlier.
 

Visitor

Well-Known Member
My luck with searching the user-contributed libraries by user name sometimes works, sometimes doesn't.

If you search by part name, then sort on the contributor column, that may make things easier. If you can't find what you want, let me know and I'll send you the files.

Locking headers are named like this, where n = 3 to 19:

HEADER-1Xn_LOCK

Locking Molex kk headers are named like this, where n = 3, 4, 5, 6:

MOLEX-1Xn_LOCK

Also available are Molex kk headers with the pins numbered in reverse order, since I've always numbered them backwards. 3 - 6 here too:

MOLEX-1Xn_LOCK-REVERSE




To ensure I leave enough clearance around mounting holes, these patterns show nut/standoff and nutdriver clearance in the document layer (which does not print on the silkscreen layer on the board).

MOUNTING_HOLE_&_PAD-3MM/4-40

MOUNTING_HOLE_3MM/4-40




To save time, I've created a standard 100mm x 100mm board outline, with mounting holes or pads. These may be helpful.

BOARD OUTLINE 100MM X 100MM W/PADS

BOARD OUTLINE 100MM X 100MM W/HOLES


Hope you'll find these footprints useful. If not, please feel free to move along without comment.
 

Pommie

Well-Known Member
Most Helpful Member
Can't seem to find them. This is what I see,
jon.png

Do you need to make them Public?

Mike.
 

Visitor

Well-Known Member
There's the problem. You're searching symbol. rather than footprint; the option is at the upper left corner of the search screen.

I use a generic header symbol for the schematic, and switch to my footprint in the properties menu for that component on the schematic view. Sorry I didn't think to mention that detail!
 

Pommie

Well-Known Member
Most Helpful Member
Still can't see them.
Here is what I see,
jon.png

I wish there was a way to only include exact matches.

Mike.
 

Visitor

Well-Known Member
They have some work to do on that.

the 6 pin header file is attached. Change the extension from txt to json and import into EasyEDA.
 

Attachments

  • PCBLIB_HEADER -1X6_LOCK_2021-07-28.txt
    7.1 KB · Views: 2

Visitor

Well-Known Member
Hack-A-Day has an article about lock footprints and alternatives. Be sure to scroll down the comments. A certain member has been immortalized for all the arguments here (since deleted).

 

rjenkinsgb

Well-Known Member
Most Helpful Member
I thought the atmosphere here was rather more pleasant recently - I did not realise why until I read Jon's post above.
A definite lack of obnoxiousness!
 

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