Electronic Lead Screws – Not Just For Threading Anymore

January 18, 2022 by Dan Maloney 6 Comments

An electronic leadscrew is an increasingly popular project for small and mid-sized lathes. They do away with the need to swap gears in and out to achieve the proper ratio between spindle speed and tool carriage translation, and that makes threading a snap. But well-designed electronic leadscrews, like this one from [Hobby Machinist], offer so much more than just easy threading.

The first thing that struck us about this build was the polished, professional look of it. The enclosure for the Nucleo-64 dev board sports a nice TFT display and an IP65-rated keyboard, as well as a beefy-looking jog wheel. The spindle speed is monitored by a 600 pulses-per-revolution optical encoder, and the lathe’s leadscrew is powered by a closed-loop NEMA 24 stepper. This combination allows for the basic threading operations, but the addition of a powered cross slide opens up a ton more functionality. Internal and external tapers are a few keypresses away, as are boring and turning and radius operations, both on the right and on the left. The video below shows radius-cutting operations combined to turn a sphere.

From [Hobby Machinist]’s to-do list, it looks like filleting and grooving will be added someday, as will a G-code parser and controller to make this into a bolt-on CNC controller. Inspiration for the build is said to have come in part from [Clough42]’s electronic leadscrew project from a few years back. Continue reading “Electronic Lead Screws – Not Just For Threading Anymore” →

KiCAD 6.0: What Made It And What Didn’t

January 18, 2022 by Dave Rowntree 56 Comments

I’ve been following the development of KiCAD for a number of years now, and using it as my main electronics CAD package daily for a the last six years or thereabouts, so the release of KiCAD 6.0 is quite exciting to an electronics nerd like me. The release date had been pushed out a bit, as this is such a huge update, and has taken a little longer than anticipated. But, it was finally tagged and pushed out to distribution on Christmas day, with some much deserved fanfare in the usual places.

So now is a good time to look at which features are new in KiCAD 6.0 — actually 6.0.1 is the current release at time of writing due to some bugfixes — and which features originally planned for 6.0 are now being postponed to the 7.0 roadmap and beyond. Continue reading “KiCAD 6.0: What Made It And What Didn’t” →

Glitch Your Way To Reverse-Engineering Glory With The PicoEMP

January 15, 2022 by Dan Maloney 9 Comments

Most of our projects are, to some extent, an exercise in glitch-reduction. Whether they’re self-inflicted software or hardware mistakes, or even if the glitches in question come from sources beyond our control, the whole point of the thing is to get it running smoothly and predictably.

That’s not always the case, though. Sometimes inducing a glitch on purpose can be a useful tool, especially when reverse engineering something. That’s where this low-cost electromagnetic fault injection tool could come in handy. EMFI is a way to disrupt the normal flow of a program running on an embedded system; properly applied and with a fair amount of luck, it can be used to put the system into an exploitable state. The PicoEMP, as [Colin O’Flynn] dubs his EMFI tool, is a somewhat tamer version of his previous ChipSHOUTER tool. PicoEMP focuses on user safety, an important consideration given that its business end can put about 250 volts across its output. Safety features include isolation for the Raspberry Pi Pico that generates the PWM signals for the HV section, a safety enclosure over the HV components, and a switch to discharge the capacitors and prevent unpleasant surprises.

In use, the high-voltage pulse is applied across an injection tip, which is basically a ferrite-core antenna. The tip concentrates the magnetic flux in a small area, which hopefully will cause the intended glitch in the target system. The video below shows the PicoEMP being used to glitch a Bitcoin wallet, as well as some tests on the HV pulse.

If you’re interested in the PicoEMP and glitching in general, be sure to watch out for [Colin]’s 2021 Remoticon talk on the subject. Until that comes out, you might want to look into glitching attacks on a Nintendo DSi and a USB glitch on a Wacom tablet.

Continue reading “Glitch Your Way To Reverse-Engineering Glory With The PicoEMP” →

An Oil Diffusion Vacuum Pump From Thrift Store Junk

January 12, 2022 by Dan Maloney 13 Comments

It seems like creating a vacuum should be a pretty easy job, but it turns out that sucking all the air out of something is harder than it seems. A cheap vacuum pump will get you part of the way there, but to really pull a hard vacuum, you need an oil diffusion pump that costs multiple tens of thousands of dollars.

Or, you need a bunch of thrift store junk, a TIG welder, and a can of WD-40. At least that’s what [Lucas] put into his homebrew oil diffusion pump. The idea of such a contraption is to vaporize oil in a chamber such that the oil droplets entrain any remaining gas molecules toward an exhaust port. His low-budget realization of this principle involved a lot of thrift store stainless steel cookware, welded together with varying degrees of success, with liberal applications of epoxy to seal up any leaks. And an electric smores cooker for the heating element, which was a nice touch. The low-budget approach extended even to the oil for the pump; rather than shelling out for expensive specialty oil, [Lucas] distilled some from a WD-40 silicone spray lubricant.

The video below details all the travails [Lucas] encountered along the way, plus the testing process. The results were at least encouraging — the diffusion pump was pulling vacuum far in excess of what the roughing pump was capable of. He clearly still has some work to do, but getting as far as he did with the scrap heap of parts he cobbled together is pretty impressive.

[Lucas]’ goal with all this? A fusion reactor. No, not that kind. This kind. Continue reading “An Oil Diffusion Vacuum Pump From Thrift Store Junk” →

Production PCB And Pogo Pins Produce A Clever Test Jig

January 7, 2022 by Dave Rowntree 13 Comments

[Hans Summers] runs a site qrp-labs.com, selling self-assembly kits mostly for radio gear and GPS applications, and had some production problems with his QCX-mini QRP transceiver kit. They were using an assembly house that had some problems with a sub-contractor going under during the pandemic, and the replacement service was somewhat below the expected level of quality, resulting in a significant number of SMT populated boards coming out non-functional. Obviously, not wanting to pass these on to customers as a debug problem, they set to work on an in-house QA test jig, to give them the confidence to ship kits again. The resulting functional test jig, (video, embedded below) takes a fairly interesting approach. Skip the video to 9:00 for the description of the test jig and detailed test descriptions.

By taking an existing known-good PCB, stripping off all the SMT parts, and moving the through hole components to the rear PCB side, pogo pins could be soldered to strategic locations. Building the assembly into a rudimentary enclosure made from sawn-up raw copper clad board, with the pogos facing upwards, and a simple clamp on top, allowed the PCB-under-test (let’s call it the UUT from hereon) to be located and clamped in place. This compressed the pogos in order to make a firm electrical contact. A piece of MDF that had been attacked with a dremel did duty as a pressure plate, with cutouts around the SMT component areas to achieve the required uniform board pressure and keeping the force away from the delicate soldered parts. All this means that with an UUT connected via pogo pins to a through-hole only test PCB, the full circuit would be completed, if and only if the UUT was completely functional, and that means defect-free soldering and defect-free components.

Next the firmware was rewritten to do duty as the test controller, which when powered up would step through a sequence of test scenarios and measurements, logging the results to an OLED display and a serial interface. This rig survived 1,000 SMT tests without failing, giving [Hans] the confidence to ship out new kits and providing a database of datalog results as a backup should a customer have an issue during final assembly. All-in-all a smart idea to solve a difficult problem, with nary a custom test jig PCB in sight!

These pages have been graced with many a pogo-based test rig over the years. Here’s one to start, and if you’ve got a handy laser cutter and some scrap wood, making an accurate test rig is no bother either.

Continue reading “Production PCB And Pogo Pins Produce A Clever Test Jig” →

A Savage Discussion Of Measurement And Accuracy

January 7, 2022 by Ryan Flowers 69 Comments

It’s commonly said that the great thing about standards is that there are so many of them. Of course, that’s talking about competing standards. But there’s another kind of standard that you want a lot of: Measurements. Without standard measurements, the Industrial Revolution wouldn’t have been facilitated to the extent it was. The illustrious [Adam Savage] takes a deep dive into the art of measurement in the video below the break, and if you have 45 minutes to spare, you will not be disappointed.

We don’t want to give away any big spoilers, but [Adam] starts out with things we can all relate to if we’ve done any kind of measuring for accuracy: measuring between the given lines on a standard tape measure. From there he goes into calipers and other tools for measurement.

Then, out come the Big Guns. The ceramic blocks so flat that… well you’ll just have to watch it. But the discussion goes deep into nanometers, microns, and jeweled movements.

Whether you’re a machinist or a garage hacker with nothing more than a stick welder and an angle grinder at your disposal, or anywhere in between in any segment of being a maker, this video is for you. [Adam]’s enthusiasm is off the charts in this diatribe, and we have to admit- it’s contagious! We’ve never been so excited about measuring things.

Of course, if you need to measurement tool, you can just build a measurement tool. It’s all subjective, after all.

Continue reading “A Savage Discussion Of Measurement And Accuracy” →

How Many Wires Do You Need To Measure A Resistor?

January 7, 2022 by Al Williams 13 Comments

Measuring resistance doesn’t seem to be a big deal. Put your meter leads across two wires or terminals and read the value, right? Most of the time that is good enough, but sometimes you need better methods and for those, you need more wires, as [FesZ] explains in his recent video that you can see below.

In the usual case, the meter applies a known voltage and measures the current which, by Ohm’s law, gives you the resistance. It is also possible to control the current and measure the voltage — doesn’t matter. [FesZ] shows how many meters measure voltage across a known resistor and the unknown so that a precision voltage or current source isn’t necessary.

But there are a number of problems with this simple method. For one thing, the test leads have resistance as well. So some voltage will drop across them, contributing to measurement error. Sure, that extra 0.5 ohms won’t matter if you are looking at a 100K resistor, but if you are trying to measure, say, the heated bed of a 3D printer, that extra 0.5 ohms is a large percentage of the total measurement.

Bench meters for lab use often support 4-wire measurements. As [FesZ] shows, this method measures three different voltages to try to negate some of the measurement errors. We liked that he used three different meters to show how it works and the difference between a 2-wire and 4-wire measurement on a small resistor.

There’s an even stranger method using 3 wires to save on wiring for, say, a sensor a long distance away. There are actually at least two ways to use 3 wires, and the video covers both of them.

For measuring resistors in a circuit, though, you need a whopping six wires. This technique uses the two extra wires to control a balance voltage that keeps the current between the unknown resistor and the rest of the circuit at zero. This prevents current flowing except for the measurement current. You’ll see a simulation of how this works in the video.

We’ve looked at 4-wire measurements before if you want some practice simulations to try. Probes for this measurement are a popular project, too.

Continue reading “How Many Wires Do You Need To Measure A Resistor?” →