Thursday, August 25, 2016

Workbench: Screw Terminal Adapters and Lever-Nuts

Having collection of connectors with screw terminals or lever clamps is very useful.  In a pinch you could do a field-repair on a headset, a rig interface, or resurrect a broken power cord with just a pocket knife and a screwdriver.  Here are some of my favorites:

DC Barrel Connectors - these can be used to make a quick disconnect (in lieu of a switch) or an extension cord.  If you just want the plug to match an existing device, you'll have to measure the outer diameter and inner pin.  Most of the time the outer dimension is 5.5mm, and the inner pin is either 1.7mm, 2.1mm, or 2.5mm.

2.1 x 5.5mm paired DC Barrel Connectors

TRS "Phono" Connectors - these are really useful for building test cables or attaching a rig interface to the ADC port on an Arduino or ESP8266.  When you get to the mountain for a SOTA activation and realize your 5 year-old has yanked the end off your headphones, you'll want one of these.

1/8" (3.5mm) Tip-Ring-Sleeve "phono male" plug

1/8" (3.5mm) Tip-Ring-Sleeve "phono female" jack

For pocket tools, I prefer the Leatherman ES4 Squirt.  ( It's a ham's dream tool, with a wire stripping jaw, knife, scissors, file, and a screwdriver bit that works well on these screw terminal adapters.

Other interesting stuff....

Wago Lever-Nuts - these are really useful for quick repairs or experiments where you want to easily connect and disconnect wires.  You can use them to quickly add sections of wire for tuning dipole antennas.  Lift the lever, slide in a wire (or wires plural) and drop the lever - done.  Made a mistake?  Lift the lever, change, drop the lever.  They'll handle up to 400 VAC and 20 amps, so they can be used for household electrical repairs or rig power cords.  I keep a handful of these in my field bag, some my glove compartment, and a bunch on my bench.  I prefer the newer 221 Series because the lever is wider and easier to manipulate.

BNC Female w/ screw terminal - these are 75 ohm, designed for CCTV installs, but for receiver testing or low-power transmit they'll work OK.  Be aware that some adapters like this actually have baluns, which you don't want for RF testing.

RJ45 screw terminal plug - kinda bulky, but it's great for designing cables on a bench.  When I'm done and have a working design, I build a real cable using CAT6 and an RJ45 crimper or a punch-down terminal block.


Jon Linthacum said...

Great Tips! Thanks David!

Jon Linthacum said...

Thanks for the tips!