- Published: Sunday, 01 August 2010
- Written by Jon Chandler
Header pins are ubiquitous on dev boards. Jumpers can be used to make connections during tests and code development but real-world applications need reliable connections. Connectors for single row headers have always been a problem for me, but I've come up with a method to achieve reliable results.
Connectors for single row headers are pretty common. You've probably used them for ISCP and seen them used for connections inside personal computers.
These connectors use crimped terminals and are relatively inexpensive. The down side is the tooling supplied by the manufacturer is extremely expensive - a hand crimper can be over $200 and the options go up from there!
Soldering these terminals is not an option - they just don't fit in the housing when soldered and the locking tab is usually screwed up.
Radio Shack sells a crimper that sort of works for these terminals. It's called a D-Sub Crimper and it costs less than $10. I say it sort of works because it lacks any mechanism to hold the wire in position while the terminal is crimped. The terminals are small and the positioning of the wire is critical.
There are two crimp areas on the terminal. The area towards the contact crimps the conductor. The area at the end of the terminal crimps the insulation to provide a strain relief. The wire must be in the correct position for a good crimp. The "official" crimp tool helps position the wire in the terminal - the cheap alternative does not.
The trick I have found is to use a short length of small-diameter heatshrink tubing as an aid. It serves both to help position the wire in the terminal and as a handle to properly align the terminal in the crimper.
Slip the heatshrink over the strain relief crimp area. Then slide the wire into the terminal, making sure the insulation doesn't extend into the conductor crimp area. The stripped wire must not extend much past the crimp area, or it will interfere with the spring contact.
The crimper has 2 layers - the shape of the crimp areas is slightly different to match the 2 areas on the terminal.
The side with the wire sizes stamped is to crimp the insulation. The unmarked side crimps a little more for the conductor side of the terminal. The terminal must be inserted in the right direction. The terminal tabs should face the rounded part of the crimper. For these terminals, the next to smallest slot on the crimper is the correct one.
Use the heatshrink "handle" to position the terminal in the crimper so that it faces fully into the slot, and the tabs on the terminal end are flush with the side of the crimper. When the terminal is correctly positioned, adjust the wire position if necessary. When everything is correct, squeeze the handles firmly together.
EDIT: At this point I actually crimp the terminal a second time, in the smallest area near the tip of crimper. Be sure to squeeze hard - the flat areas on the crimpers should almost touch with a proper crimp.
The heatshrink is pulled back to reveal a nice crimp. The terminal is ready to be inserted into the housing. The picture below shows the locking tab. Line it up with the slot in the connector shell and push the terminal into the housing until it clicks.
When all the wires are in the connector, I like to twist the wires together.
It goes without saying that the terminals must match the housings. The wire size must also match the terminals.
The following terminals and housings work together.
|Positions||With Locating Ribs||No Locating Ribs|