Homebrew Curve Tracer Competes With The Big Guns

When we first saw the VBA curve tracer, we thought it might have something to do with Visual Basic for Applications. But it turns out it is a mash up of the names of the creators: [Paul Versteeg], [Bud Bennett], and [Mark Allie]. [Paul] designed an original prototype back in 2017. Since then, the project has grown and lessons were learned. The final curve tracer is pretty impressive in more ways than one.

If you’ve never used a curve tracer, they allow you to characterize components using their characteristic curve of voltage versus current. You use an oscilloscope as an output device. This instrument is often used by engineers trying to understand or match devices like diodes, transistors, or — in some cases — even tubes. So if you want to measure the collector-emitter breakdown voltage, for example, or the collector cutoff current, this is your go-to device. You can also match gains in circuits where that matters (for example, a push-pull circuit where two transistors amplify different parts of the same signal).

If you want to understand more about how it works, there are a series of blog posts covering the evolution of the device. You can also find the design files on GitHub. There is also a handy post showing many types of measurements you might want to make.

This is a good-looking project. We’ve seen it done on the cheap, but slowly. Or spend $15 and do better. We doubt any of these have high enough voltages to do most tubes, but they made the same basic instrument for tubes back in the 1950s.

Upside-down c-clamp held in a frame, forming a crude press

C-Clamp Becomes Light-Duty Arbor Press

[ThingaUser] made a tool to solve a specific problem of theirs, but the design also happens to be a pretty good way to turn a c-clamp into a poor man’s light duty arbor press.

The frame is made for a common 4-inch c-clamp.

The problem they had was a frequent need to press nuts and occasionally bearings into other parts. Some kind of press is really the best tool for the job, but rather than buy a press, they opted to make their own solution. By designing and 3D printing an adapter for a common 4-inch c-clamp, a simple kind of light duty press was born.

Sure, one has to turn the handle on the clamp to raise and lower the moveable jaw, and that’s not the fastest operation. But the real value in the design is that the clamp can now stand by itself on a tabletop, leaving the operator to dedicate one hand to manipulating the part to be pressed, while twisting the clamp’s handle with the other hand. There’s no need for a third hand to keep the clamp itself stable in the process. As a bonus, it can print without supports and the clamp secures with zip ties; no other fasteners or glue needed.

Not all c-clamps are the same, so there is a risk that this frame that fits [ThingaUser]’s clamp might not fit someone else’s. In those cases, it’s best to have access to not just the STL file, but also to a version in a portable CAD format like STEP to make it easy to modify. But there are still ways to make changes to an STL that isn’t quite right.