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?” →

Remoticon 2021: Unbinare Brings A Reverse-Engineering Toolkit Into Recycling

January 6, 2022 by Arya Voronova 5 Comments

Unbinare is a small Belgian company at the forefront of hacking e-waste into something useful, collaborating with recycling and refurbishing companies. Reverse-engineering is a novel way to approach recycling, but it’s arguably one of the most promising ways that we are not trying at scale yet. At Hackaday Remoticon 2021, Maurits Fennis talked about Unbinare’s efforts in the field and presented us with a toolkit he has recently released as a part of his work, as well as described how his background as an artist has given him insights used to formulate foundational principles of Unbinare.

Unbinare’s tools are designed to work in harmony with each other, a requirement for any productive reverse-engineering effort. OI!STER is a general-purpose salvaged MCU research board, with sockets to adapt to different TQFP chip sizes. This board is Maurits’s experience in reverse-engineering condensed into a universal tool, including a myriad of connectors for different programming/debugging interfaces. We don’t know the board’s full scope, but the pictures show an STM32 chip inside the TQFP socket, abundant everywhere except your online retailer of choice. Apart from all the ways to break out the pins, OI!STER has sockets for power and clock glitching, letting you target these two omnipresent Achilles’ heels with a tool like ChipWhisperer.

Continue reading “Remoticon 2021: Unbinare Brings A Reverse-Engineering Toolkit Into Recycling” →

A Simple Touch Probe Made With Basic Tools

January 5, 2022 by Dave Rowntree 14 Comments

Six points of contact detect any displacement.

LinuxCNC contributor and machining enthusiast [Andy Pugh] is certainly not afraid to try making specialised tools to see how well they work out, and this time he’s been busy making a touch probe (video, embedded below) for checking the accuracy of machining operations and general measuring applications.

These things are not cheap, since they are essentially ‘just’ a switch with a long probe, But, as with anything specialised and machined with tight tolerances, you can understand why they cost what they do.

After inspecting and spending some time reverse-engineering such a unit, [Andy] then proceeded to grab some PEEK bar he had lying around and chuck it into the lathe (get it?). He notes Delrin would be more cost effective for those wishing to reproduce this, but as long as you have the ability to machine it and it’s non-conductive, there are many other options you could try.

Using no special tools other than a collet block (like this one) all the angled holes and slots were made with ease, with the help of a specially 3D-printed mount for the vise. A nice, simple approach, we think!

[Andy] tested the repeatability of the probe, mounted over his CNC-converted Holbrook lathe, reporting a value of 1 um, which seems rather good. Centering of the probe tip within the probe body was off a bit, as you’d expect for something made practically by hand, but that is less of a problem as it would seem, as it results in a fixed offset that can be compensated for in software. Perhaps the next version will have some adjustability to dial that out manually?

The whole assembly is formed from two plastic parts, a handful of ground-finished hardened steel pins, and a big spring. The only part remotely special is an off-the-shelf probe tip. During the electrical hookup, you may notice the use of a self-fluxing verowire pen, which was something this scribe didn’t know existed and has already placed an order for!

The reference 3D model for the design is shared from [Andy]’s Autodesk Drive for your viewing pleasure.

Of course, this isn’t the first DIY touch probe we’ve seen, here’s one for example, and over on Hackaday.IO, here’s an attempt to make one using a piezoelectric transducer.

Continue reading “A Simple Touch Probe Made With Basic Tools” →

USB Power Has Never Been Easier

January 5, 2022 by Brian McEvoy 48 Comments

USB cables inevitably fail and sometimes one end is reincarnated to power our solderless breadboards. Of course, if the cable broke once, it is waiting to crap out again. Too many have flimsy conductors that cannot withstand any torque and buckle when you push them into a socket. [PROSCH] has a superior answer that only takes a couple of minutes to print and up-cycles a pair of wires with DuPont connectors. The metal tips become the leads and the plastic sheathing aligns with the rim.

The model prints with a clear plus sign on the positive terminal, so you don’t have to worry about sending the wrong polarity, and it shouldn’t be difficult to add your own features, like a hoop for pulling it out, or an indicator LED and resistor. We’d like to see one with a tiny fuse holder.

If you want your breadboard to have old-school features, like a base and embedded power supply, we can point you in the right direction. If you are looking to up your prototyping game to make presentation-worthy pieces, we have a host of ideas.