Introduction: New Terminal Connector Options for Circuits

A common way to connect wires to a circuit is to use a male or female header. While this type of connection is useful, it has two drawbacks - 1) a connector must be fitted to any connecting wires and 2) it isn't a very reliable connection. Screw terminals are often used to remedy these problems, but they are much larger (having 0.2" spacing instead of 0.1") and require tools to connect the wire. I have found two connectors that address these problems. They both have only 0.1" pin spacings just like headers, and one is spring-loaded and requires no tools.

Spring Loaded Terminals
In the first photo, you can see both a 2-pin and two 4-pin spring terminals in action. These terminals are surprisingly inexpensive and readily available at Digikey. They offer only 0.100" spacing between pins and require only a finger to hold the clamp away from the wire while the wire is inserted. Releasing your finger will secure the wire. They are really easy to use.

Their drawbacks are the extra depth they require for the spring mechanism and the staggered pin locations. You must be careful of this fact when creating your footprints. The manufacturer always puts the rightmost pin (when looking at the front) closest to the front. See the 2nd and 3rd photos for details. You also need to note that the connector has a little part on the left which keeps them from being stacked like screw terminals. You can still stack them, but you need to plan your PCB in advance. The 1st and 3rd photo shows two 4-pin terminals side by side. You can see the extra spacing required.

PCB Tip: If you look at photo #3, you can see that I created two sets of pads for each pin. I also connected these together. That way, I have the option of using these spring terminals, or something else such as headers or screw terminals.

You can obtain these parts for only about 10 cents per pin at Digikey. Here are some Digikey part numbers:
  • 2-pin:  277-1794-ND
  • 3-pin:  277-1795-ND
  • 4-pin:  277-1796-ND
  • 6-pin:  277-1798-ND

Small Screw Terminals
Screw terminals are another great option for attaching wires to your PCB. The main drawback is their huge size. Their pins are 0.197" apart. For smaller boards, this becomes a big problem. There is a solution. Digikey also carries a small screw terminal with only 0.100" spacing.

If you examine the last three photos, you can see that these connectors are identical to their bigger cousins - they have inline pins, they are stackable, and use a screw on the top to clamp the wire in place.

The drawbacks to these connectors are two:
  1. They require a small jeweller or eyeglass screwdriver to operate. Most people don't have such a small screwdriver.
  2. They are a little pricey in comparison to the larger ones.
Despite these two drawbacks, you can't beat the size advantage or the fact they are a drop in replacement for a row of headers. You can also buy these at Digikey. Here are some part numbers:
  • 2-pin:  A98333-ND
  • 3-pin:  A98334-ND
  • 4-pin:  A98335-ND
  • 6-pin:  A98337-ND
Last Remarks
Both of these terminals come in other pin configurations as well, so check out the Digikey pages for what you need.

I have Diptrace footprints for the spring terminals, so if you use Diptrace and would like a copy of these footprints, let me know and I'll try to post them to my website.

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