Printed Parts Turn Ruler Into Marking Gauge

November 7, 2018 by Tom Nardi 19 Comments

For Hackaday readers who spend more time with a soldering iron than a saw, a marking gauge is a tool used to put parallel lines on a piece of wood (and occasionally metal or plastic) for cutting. The tool is run across the edge of the piece to be marked, and an adjustment allows the user to set how far in the line will be made. As an example, if you wanted to cut a board into smaller strips, a marking gauge would be an ideal choice for laying out your lines ahead of time.

But as with many niche tools, it’s not something you’re going to use every day. For [chaosbc], this meant he wanted to see if he could come up with a DIY solution on the cheap. Plus he could have it in hand now, rather than waiting for it to take the slow boat from overseas. With the addition of a few clever 3D printed components, he was able to turn his trusty aluminum ruler into a serviceable marking gauge for the cost of filament and a few bits of hardware.

The general design of a marking gauge is fairly simple: there’s a block that rides up and down a graduated shaft (known as the headstock) which allows you to set the depth of the line, and then a piece on the end which holds your marking tool. The marking tool could be a blade if you’re working with something soft enough, but for wood is usually going to be a pencil.

[chaosbc] provides all the STL files for his DIY marking gauge, though they might need adapting as they were created for his specific ruler. Luckily the parts aren’t that complex so it shouldn’t be too difficult to get it sorted out. He also has a useful hint for anyone looking to duplicate his work: a few drops of super glue on the bolt used to lock down the headstock is enough to create a non-marring surface so you don’t tear up your ruler.

We’ve got a few other tips for woodworking on a budget, as well as a primer about this whole making stuff with dead trees concept.

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Junkbox Constant Current Source Helps With Kelvin Sensing

November 7, 2018 by Dan Maloney 3 Comments

Is it ironic when a YouTube channel named “The Current Source” needs to build a current source? Or is that not ironic and actually just coincidental?

Regardless of linguistic considerations, [Derek], proprietor of the aforementioned channel has made and disassembled a few current sources in his day. Most of those jobs were for one-off precision measurements or even to drive a string of LEDs in what he describes as a pair of migraine-inducing glasses. Thankfully, The junk box current source presented in the video below is more in service of the former than the latter, as his goal is to measure very small resistances in semiconductors using Kelvin clips.

The current source uses a 24-volt switch-mode power supply and the popular LM317 adjustable voltage regulator. The ‘317 can be configured in a constant current mode by connecting the chip’s adjustment pin to the output through a series resistance. A multiturn pot provides current adjustment, although the logarithmic taper is not exactly optimal for the application. We spotted a pair of what appear to be optoisolators in the build too, but there’s no schematic and no discussion of what they do. [Derek] puts the final product to use for a Kelvin measurement of a 0.47-Ω 1% resistor at the end of the video.

We’re glad to see [Derek] in action; you may recall his earlier video about measuring his own radiation with a Geiger counter after treatment for thyroid cancer. Here’s hoping that’s behind him now.

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Teardown Of A (Relatively) Cheap Thermal Camera

November 7, 2018 by Tom Nardi 32 Comments

The cost of tools and test equipment has largely been on the downward trend for years, making it now more affordable than ever to get into the hacking and making scene. This is particularly visible with something like the venerable oscilloscope: a piece of equipment that was near unobtainium for the home hacker a decade ago, you can now get digital pocket scope for as little as $20 USD. But there are still pieces of gear which haven’t quite hit the sort of prices we’d like to see.

A perfect example are thermal imaging cameras. The cheap ones are usually so low resolution they might as well just be thermometers, but the higher resolution ones can cost thousands. [Rob Scott] recently wrote in to tell us about a very promising middle ground, the HTI HT-A1. But he didn’t just point it out to us, he also tore it down and laid its internal’s bare for our entertainment. Now that’s our kind of introduction.

[Rob] walks us through the disassembly of the device, which is made unnecessarily difficult due to the fact that half the screws are hidden under a glued on screen bezel. That means a heat gun, a thin tool, and patience are in order if you want to get inside the device. It’s bad enough they use these kinds of construction techniques on modern smartphones, but at least they’re so thin that we can understand the reasoning. Why this chunky thing needs to resort to such measures is beyond us.

Eventually he cracks the HT-A1 open and is greeted with a single double-sided PCB. The top side is pretty much bare except for the buttons and the LCD display, and the flip side is largely just a breakout for a quad-core Allwinner A33 daughterboard. [Rob] theorizes this is to keep costs down by allowing reuse of the modular A33 board on other devices. Given the A33’s use in so many cheap tablets, it’s also possible HTI simply purchased these daughterboards as a drop-in component and designed their own board around it.

There’s not much else inside the HT-A1 beyond the rechargeable battery pack and thermal camera, both attached to the device’s rear panel. [Rob] noticed that the date on the thermal camera PCB is a full two years older than the date on the main PCB, leading one to wonder if HTI might have gotten a good deal on a bunch of these slightly outdated sensors and spun up a whole device around them.

The HT-A1 is high enough resolution that you can actually pick out individual components on a PCB, and at $400 USD is approaching a reasonable price point for the individual hacker. Which is not to say it’s cheap, but at least you get a useful tool for your money. We wouldn’t suggest you buy this device on a whim, but if you do a lot of diagnostic work, it might pay for itself after a couple repairs.

If that’s still a little too rich for your blood, we’ve covered a handful of DIY options which might better fit your budget.

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Homebrew Attachment Turns Angle Grinder Into Slimline Belt Sander

November 5, 2018 by Dan Maloney 7 Comments

If there’s a small power tool as hackable as the angle grinder, we haven’t found it yet. These versatile tools put a lot of power in the palm of your hand, and even unhacked they have a huge range of functionality, from cutting to grinding to polishing and cleaning, just by choice of what goes on the arbor.

With a simple homebrew attachment, [Darek] turned his angle grinder into a micro-belt sander that’s great for those hard-to-reach places. The attachment that clamps where the disc guard normally lives adds a drive roller to the grinder’s arbor; idler rollers ride on the end of a small pneumatic spring that keeps the belt under tension. The belts themselves are cut down from wider sanding belts, and the attachment can take belts of various widths. And best of all, he did it all without any fancy machine tools. No lathe? No problem – the drive roller was ground to the proper crowned profile needed to keep belts centered using the angle grinder itself. The only problem we see is that the attachment can’t be easily removed from the grinder, but that’s OK. Grinders are like potato chips, after all – you can’t stop at one.

This isn’t [Darek]’s first angle grinder hacking rodeo, of course. And if you’re looking for inspiration on how to hack yours, look no further: a floor sander, a precision surface grinder, or even an e-bike can be built.

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Scratch Built Toe Clamps Keep Your Work In Place

November 5, 2018 by Donald Papp 15 Comments

[Kevin] owns a benchtop CNC mill that has proven itself to be a capable tool, but after becoming familiar with some of its shortcomings, he has made a few modifications. In order to more efficiently hold and access workpieces on his custom fixturing table, he designed and made his own toe clamps and they look beautiful.

The usual way to secure a piece of stock to a fixturing table is to use top-down clamps, which hold the workpiece from the top and screw down into the table. However, this method limits how much of the stock can be accessed by the cutting tool, because the clamps are in the way. The most common way around this is to mount a vise to the table and clamp the workpiece in that. This leaves the top surface completely accessible. Unfortunately, [Kevin]’s benchtop Roland MDX-450 has a limited work area and he simply couldn’t spare the room. His solution was toe clamps, which screw down to the table and have little tabs that move inwards and downward. The tabs do the work of clamping and securing a piece of stock while maintaining a very low profile themselves.

The clamp bases are machined from stainless steel and the heads are brass, and the interface between the two is a set screw. Inserting a hex wrench and turning the screw moves the head forward or back, allowing a workpiece to be clamped from the sides with minimal interference. His design was done in Fusion 360 and is shared online.

Another option for when simple clamps won’t do the job is a trick from [NYC CNC], which is to use an unexpected harmony of blue painter’s tape and superglue which yields great results in the right circumstances.

Flexible Battery Meter Bends Over Backward To Work

November 2, 2018 by Dan Maloney 7 Comments

A lithium-ion battery tester seems like a simple project, at least electrically. But when you start thinking about the physical problem of dealing with a huge range of battery sizes, things get a little more complicated. Sure, you can 3D-print adapters and jigs to accommodate the different batteries, or you can cheat a bit and put the charger and tester circuit on a flexible PCB.

Maybe it’s the Kapton talking, but we really like the look of [Androkavo]’s project. The idea is simple – rather than use a rigid FR4 printed circuit board, a flexible polyimide film PCB a little longer than the biggest battery to be tested was fabricated. With large contacts on each end, the board can just be looped across the battery to take a reading. For charging, neodymium magnets on the other side of the board keep the charger in contact with the battery. The circuit itself is built around an STM8S003 8-bit microcontroller and a handful of discrete components. There’s a bar graph display for battery voltage that covers 2.0 to 4.9 volts, and a USB port for charging. The charger works with everything from the big 21700 cells down to the short 14500s. With the help of another magnet to keep the board from bending too sharply, even the diminutive 10180 can be charged. Check out the video below, which has some of the most relaxing music and best microscope shots of SMD soldering we’ve seen.

Flexible PCBs are versatile things. Not only can they make projects like this successful, but they can also wriggle around, swim, or even play music.

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Cut Through The Noise, See Tiny Signals

November 1, 2018 by Bryan Cockfield 18 Comments

An oscilloscope is a handy tool for measuring signals of all kinds, but it’s especially useful if you want to measure something with a periodic component. Modern oscilloscopes have all kinds of features built-in that allow you sample a wide range of signals in the hundreds of megahertz, and make finding and measuring your signal pretty easy, provided you know which buttons to push. There are some advanced oscilloscope methods that go beyond the built-in features of even the best oscilloscopes, and [AM] has a tutorial on one of them.

The method used here is called phase-senstitive detection, and allows tiny signals to be found within noise, even if the magnitude of the noise is hundreds of times greater than the signal itself. Normally this wouldn’t be possible, but by shifting the signal out of the DC range and giving it some frequency content, and then using a second channel on the oscilloscope to measure the frequency content of the source and triggering the oscilloscope on the second channel, the phase of the measured signal can be sifted out of the noise and shown clearly on the screen.

In [AM]’s example, he is measuring the intensity of a laser using a photodiode with a crude amplifier, but even with the amplifier it’s hard to see the signal in the noise. By adding a PWM-like signal to the power source of the laser and then syncing it up with the incoming signal from the photodiode, he can tease out the information he needs. It’s eally a fascinating concept, and if you fancy yourself a whiz with an oscilloscope this is really a tool you should have in your back pocket. If you’re new to this equipment, we do have a primer on some oscilloscope basics, too.

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