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.

What You Should Know Before Buying An Industrial Sewing Machine

January 4, 2022 by Kristina Panos 48 Comments

I’ve been sewing off and on since I was a kid, and I really started to get into it about ten years ago. Even though I technically outgrew my little 3/4 size domestic machine pretty quickly, I kept using it because it always did whatever I asked it to. I even made my first backpack on it before deciding it was time for something bigger. Don’t ask me how I managed to not kill that machine, because I have no idea.

Left: a 3/4 size Janome 11706. Right: a full-size Singer Heavy Duty 4452.

Last year, I got a so-called heavy duty Singer that claims to have 50% more power than a standard domestic machine. This bad boy will make purses and backpacks with ease, I thought. And it does. Well, most of the time.

I found its limits when I tried to make a bag out of thick upholstery material. And honestly, when it comes down to finishing most bags — sewing the thickest and most difficult seams — the machine often lifts up from the table on the end opposite the needle.

What I really need is an industrial sewing machine. Not to replace the Singer at all, but to complement it. I can totally justify this purchase. Let me tell you why.

Continue reading “What You Should Know Before Buying An Industrial Sewing Machine” →

Angel Investor Gives Open Source PnP A Massive Boost

January 4, 2022 by Dave Rowntree 18 Comments

We love it when an Open Source hardware project grows up and turns into a sustainable business, bootstrapped with nothing but hard work and great ideas, but it’s a really tough prospect to do it using your own money, ploughing the profits from any sales back into development and not taking a dime in wages whilst you do so. People obviously need an income to live off, and that time spent working on a startup is time you can’t spend earning your keep. So it’s with great pleasure that we can bring you the latest news from [Stephen Hawes] and his pick-and-place machine plans. In the year since we last checked in with the project, development has continued at a steady pace, with the guys quickly outgrowing the garage workspace, whilst they prepare PnP machine kits ready for sale.

The big news is that [Joel Spolsky], co-founder of Stack Exchange, creator of Kanban management tool, Trello, and angel investor, has made a sizable ($100K USD) investment in the company which has allowed them to take on a 3,000+ sq. ft office space, and given them the funds for stock and all that boring business overhead stuff. [Stephen] takes time to explain that [Joel] will not have any control of the company, and all hardware and software will remain fully Open Source. For those interested [Joel] implemented his investment as a SAFE note (Simple Agreement for Future Equity) and as such, [Joel] will only make a return in the form of a small share allocation, if they hit the big-time in the future. Can’t really say fairer than that!

[Stephen] did recently receive a ‘cease and desist’ notice regarding his use of the ‘Index’ name for the project, since that is already a trademarked term, defended by somebody else, the project will need change name very soon. A minor setback, but it is a bit annoying that a chunk of that investment now has to go to a lawyer to make sure that the name they do eventually choose isn’t already taken and is safe to use.

In terms of the machine itself, it is now is fully operating, with multiple automatic tape feeders, featuring up and down-facing machine vision, and all that OpenPnP goodness. It has even been demonstrated placing parts for its own custom motherboard PCB, reprap style. Nice!

We wish [Stephen] and partner [Lucian] all the success they deserve, and hope they get those kits out there, because there are people around these parts that need an affordable, hackable, desktop PnP machine ASAP, this scribe included!

Here’s the earlier story covering the machine, but it’s not the only Open Source PnP machine we’ve seen – here’s another one from a few years ago.

Continue reading “Angel Investor Gives Open Source PnP A Massive Boost” →

Need A Small, Cheap Ammeter? Blinkenlights To The Rescue!

January 3, 2022 by Ryan Flowers 3 Comments

You know how it is. You’ve got that new project running, and while it doesn’t consume much power, it also doesn’t give much indication of whether it’s functioning or just sitting there with a dead battery. What you need is an ammeter to check power consumption, even from across the room. And it just so happens that [Manuka] has Just The Circuit You Need, complete with a demonstration in the video after the break!

Oh sure, you could grab a cheap ammeter at your favorite tool import store or site, but those are bulky and take batteries. You could put in an LED that gets dimmer as voltage drops. But wait- is that the sun shining on it? or is it on? Or has something gone awry and it’s consuming too much power?

What [Manuka] gives us is a circuit that is designed to be built into your project or project’s power supply. Using only an ultra-bright white LED, red blinking LED, PNP transistor, and a diode, the circuit gives a strong visual indication of current consumption by blinking brighter and more frequently as current increases. With a bit of calibration, accurate measurements can be obtained. All of this is made possible by using the Flashing LED as a driver for the ultra-bright LED, which is a pretty slick hack!

Flashing LEDs have a great number of uses, like protecting your family from lions. Yes, really. Got a cool tip for flashing LEDs, blinkenlights, 555’s, or any odd thing that strikes your hackers fancy? Let the tip line know!

Continue reading “Need A Small, Cheap Ammeter? Blinkenlights To The Rescue!” →