2
\$\begingroup\$

So, now that I have a bench power supply (0-+/-25V at 0-1A, 0-6V at 0-5A) on my bench, I need a set of test leads for it. Considering that I have had variable experiences with power supply test leads in the past, and that bench clutter is a major issue for me, I was planning on making my own up vs. buying premade leads.

Wire

For the wire, instead of using test lead/prod wire (whether PVC or silicone insulated), I was thinking of using UL AWM 2468 or equivalent "zip lead" that is more typically used for the output leads of DC wall adapters. This has the advantages of keeping the number of leads and the amount of bench clutter down, while having reasonable properties (80°C temperature rating) and availability. It's also available with pre-molded barrel plug ends, which is useful as it's difficult to homebrew proper strain relief for a barrel plug.

However, despite these upsides, I still have doubts as to whether this type of wire would be suitable under workbench-test-lead conditions; furthermore, the thickest I can get it in is 18AWG -- is this thick enough for a set of bench supply test leads, or should I be using thicker wire yet?

Connectors

Other than the barrel plug ends, I am going to be terminating these with header pins (for direct connection to breadboards) and stackable banana plugs (both on the other end of leads that connect to breadboards or PCBs, and in the banana-to-banana case). This leads me to my other main line of inquiry: what is the best way to attach stackable banana plugs to test leads? I have my choices between:

  • Solder-attach (where the wire is put through a hole in the contact piece, soldered, and then folded back into the housing when the housing is fitted)
  • Setscrew-attach (where a clamping setscrew is used to "pin" the lead wire to the contact assembly in a back-wired arrangement), and
  • Spring-clamp-attached (where a pushbutton-operated spring-clamp replaces the setscrew for holding the wire to the contact assembly).

Which one of these would yield the best reliability under bench conditions?

\$\endgroup\$

1 Answer 1

Reset to default
2
\$\begingroup\$

If it is NOT for (semi-)permanent setups, but it is for acutual "heavy-duty" bench work, I'd stay away from anything than silicone-rubber-insulated multi-stranded wires. If a hot soldering iron is around it is extremely easy to melt away a simple PVC insulation, and the fact that the positive and negative wires are kept so close together means a guarantee for nasty shorts if you are unlucky (especially if the power supply can deliver high current spikes).

Moreover, good silicone rubber insulation together with multi-strands makes your life better when handling wires on your bench: they don't stick to each other and to other wires (DMMS, scopes, etc.) and it is easier to move them around without dragging lots of things with them!

Moreover, these kind of wires are made to be moved all the time. Normal PVC insulation might not survive well the "hard life" of the bench top. You could end with an insulation with cracks and cuts that can fail you just in the worst possible moment.

\$\endgroup\$
5
  • 1
    \$\begingroup\$ I'd like to add that actual (real test leads/wire, not the el-cheapo scary ones) test leads are designed for the wire to flex... repeatedly. The conductors in light-duty zip cord will break with repeated flexing. Advice: Don't roll your own. Buy a quality set and be done with it. \$\endgroup\$
    – R Drast
    Nov 8, 2017 at 9:18
  • 1
    \$\begingroup\$ @RDrast Yep, definitely, for the first part. However, you could roll your own, and you could do a good job without spending a fortune. When I was much younger, and having very little money, I rolled my own, and I still have most of those cables. The secret was to buy quality components. They still cost me a lot (especially silicone insulated wire), but the result was ten times cheaper than pre-made ones. Of course you must be reasonably skilled with soldering and crimping and have a decent soldering iron with enough power. \$\endgroup\$
    – Lorenzo Donati support Ukraine
    Nov 8, 2017 at 21:09
  • \$\begingroup\$ @RDrast -- the problem with the "buy them off the shelf" approach is that the commercial sets do things I don't have much use for (alligators, spade lugs) while not providing stuff I do need (pin headers, barrel plugs) \$\endgroup\$
    – ThreePhaseEel
    Nov 10, 2017 at 0:38
  • \$\begingroup\$ @ThreePhaseEel You can roll your own small adapters for those. There are small-diameter silicone-rubber wires which you can fit into a barrel plug on one side and into banana plugs on the other, just for example. \$\endgroup\$
    – Lorenzo Donati support Ukraine
    Nov 10, 2017 at 6:10
  • \$\begingroup\$ @ThreePhaseEel But, as I said in my answer, if you need a (semi-)permanent setup where the wires are almost always plugged in the PS and in a device (i.e. Arduino), and you can ensure the wires don't run across your bench (i.e. they stay out of the way), then zip wire or other PVC wires could be a good solution. But if they are exposed to frequent movements or mechanical/thermal stress you could end up regretting dearly those cost savings. Just the fact that PVC wires tend to be much more rigid could end up annoying you in the long run. \$\endgroup\$
    – Lorenzo Donati support Ukraine
    Nov 10, 2017 at 6:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.