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June 2021: In search of the perfect pin socket

A project log for Modular differential probe

100 MHz differential probe for oscilloscopes, with modular accessories to suit both high and low voltage use.

petteri-aimonenPetteri Aimonen 08/06/2021 at 13:030 Comments

2.54 mm pitch pin headers with 0.6 mm square pins are pretty much the de-facto prototyping connector for all low voltage uses. Many grabber hooks and cables are designed to fit this. But there is considerable variation: sometimes the 0.6 mm pins are instead round or U-shaped. And usually the cable-mounted so called "DuPont connectors" do not last very long before they start making a poor connection. I certainly don't want to ruin the probe usability by having a flaky accessory.

Because I want to minimize the probe capacitance, there is the extra complication that the pin socket connector must be mounted on a small PCB with 0603 resistor and capacitor on it. That then gets soldered to the end of a coaxial cable and heatshrinked - and it should still fit between 2.54 mm pitch pins!

After a bit of searching, I found Mill-Max 0279-0-15-15-47-27-10-0 sockets. They are tiny, yet have real gold-plated six-sided spring mechanism inside. This should last much longer than the tin-plated one-sided springs.

Best of all, it fits on a tiny PCB and the width is 2.3 mm with a single layer of heatshrink applied. Because the shaft has hex-shaped protrusions, it should work in a reflow process also - at least if placed manually.

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