- Published: Sunday, 10 July 2011
- Written by Jon Chandler
- Hits: 5407
Header connectors are ubiquitous on dev boards for making connections between boards and for connecting all types of external devices. The TAP-28 board uses 3-pin and 6-pin single-row header connectors for everything.
As prevalent as these connectors are, making connections isn't a trivial matter. Crimp connectors are common, but assembling them isn't simple. A previous article provided some tips on putting these connectors together but it's still been a time-consuming, not-wholly-successful task. After looking at the options, I've found a better method.
Amp's MTA connectors are IDC single row connectors for individual wires. The connectors go together easily and are very inexpensive compared to crimp-type connectors. The photo below shows a few examples of these connectors. They are available with a range of contacts from a number of vendors.
In this photo, you can see the metal IDC contacts and the barbs on the housing to hold the wires in place before they are inserted. The contact cuts through the cable jacket so it's not necessary to strip the cable before assembly. The blue arrows pointing to the white connector show an optional feature - alignment tabs. If a keyed header is used, these tabs ensure that the connector is properly aligned (i.e., not put together one pin off).
The two photos below show a connector mated to a keyed header.
A special punchdown tool is required to assemble these connectors. It's about US$25, which seems slightly expensive, but if you compare the cost of connectors and value your time, the value quickly becomes apparent.
Using these connectors couldn't be any easier (at least not without a much more expensive auto-insert tool). Line the wire up, and poke it down using the tool. I've built a little jig to hold the connector in place which reduces the need to have 3 hands. The next photo shows the wire in place.
And it's a simple matter to insert it using the tool.
The five wires I need are finsihed in seconds.
The connectors are available in two configurations. The photo above shows a closed connector - the wires can only exit from one side. They are also available in an open type - the wires can extend in both directions. In the photo below, the white connector is the open type, the red is a closed type.
Using open type connectors permits making daisy-chain cables with connectors along the length. The cable I'm building here is for use with the TAP-20-USB board - an intermediate connector will be used to connect to the PICkit 2. Each wire continues through the second connector. The photo below shows the wires aligned and ready to be inserted.
And the wires are simply poked home.
Here's the final cable assembly. The far end of the cable will be spliced to a USB-A cable.
As handy as these connectors are, there is one major limitation. The right gauge of wire must be used with each connector. There is no tolerance in this regard. The connectors are color-coded to indicate the wire size.
In case you're wondering why my connectors aren't assembled directly on the end of the USB cable, the power conductors in most USB cables are a larger gauge than the signal conductors. One size of connector cannot accommodate the different gages.
Jameco Electronics has the best prices on these connectors that I have seem. $0.09 each at quantity 1. The punchdown tool is US$30 however. It's considerably cheaper at Digikey. Jameco Catalog Page. You may find better prices elsewhere.