Grinding Coffee Beans The Machine Shop Way

April 28, 2021 by Kristina Panos 31 Comments

Okay, so you bought a bag of heavenly-smelling single-origin beans down at the hipster coffee shop, but forgot to have them ground. What do you do? If you’re [Jimmy DiResta], there’s no way you can run down to Walmart and pick up a grinder for $15. You commune with your tools and spend a few hours building a grinder from stuff lying around in the workshop.

This hand-crank grinder would make a great post-apocalyptic appliance, as long as we still have a way to heat water. [Jimmy] started with an old manual abrasive disc grinder, like for grinding metal, not beans.

After oiling it up to run without a hitch, he pulled out a couple of conical gears and got to work mounting one to the grinder shaft and the other to the business part of a vintage industrial light fixture.

We thought for sure this was going to be a burr grinder, but were a bit disappointed to watch [Jimmy] drill holes through a utility knife blade in order to make a blade grinder. Honestly, we’re kind of surprised that he didn’t machine some burrs, but the result is impressive and lovely nonetheless.

We love that the whole thing quick-disconnects from the grinder thanks to a custom cuff that holds the light bulb just so, we just hope that [Jimmy] gave that light bulb a good cleaning first. Grab a cup of whatever and check out the build video after the break.

Not exactly your kind of shop? You could always print an emergency coffee grinder.

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DIY Grader Box + Rocks = No Need For Shocks

April 27, 2021 by Kristina Panos 17 Comments

Between the mini bike and the nearby woods, [HowToLou] has a lot for the rest of us to be envious of. Unfortunately, the terrain on the dirt path is too bumpy and uneven for a nice ride. But rather than spend hundreds to buy or rent an official grader box, [Lou] looked at his riding mower and said, I can do that myself (YouTube, embedded below).

This grader box is made from a heavy-duty oak pallet, plus a piece of particle board to complete the rocks box. [Lou] hooks up tow straps to the hooks and drags it behind the riding mower a few times to get the path nice and even. The line of lag bolts busts up the bumps, and the boards smooth out the surface under the weight of several large rocks. We think the result looks great, and doubt that [Lou] could have done any better with a fancy grader box. Check it out in action after the break.

Don’t have a riding mower? This is a pretty good excuse to buy one, but if that’s not in the cards, maybe you could build something suitable out of plywood and bike parts.

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Logic Flows, Literally, In This Water Adder

April 26, 2021 by Al Williams 31 Comments

A lot of elementary electronic texts use water as an analogy for electricity. You know, pressure is voltage, flow is current, and pipe diameter is resistance. It is ironic, then, that some people use fluids to build logic gates and, in fact, you can make any logic circuit you like using nothing but water flowing through some structures. Don’t think so? Have a look at the video from [Steve Mould] below.

Fluidic logic isn’t anything new, but it has always been a bit exotic. Usually, replacing electrons with water or even air — which is a kind of fluid — means you are trying to operate in a tough environment or have some other special need. As far as we can tell, [Steve] did it just because he could, and we get that.

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3D-Printed Laser Scanning Confocal Microscope Measures Microns

April 26, 2021 by Dan Maloney 15 Comments

When one thinks about microscopy, it seems to be mostly qualitative. Looking at a slide teeming with bacteria or protozoans is less about making measurements and more about recognizing features and describing their appearance. Not all microscopes are created equal, though, with some being far more optimized for making fine measurements of the microscopic realm.

This 3D-printed confocal laser scanning microscope is a good example of an instrument for measuring really small stuff. As [Zachary Tong] points out, confocal scanning microscopy uses a clever optical setup to collect light from a single, well-defined point within a sample; rather than getting an image of all the points within a two-dimensional focal plane, the scanning function moves the focal point around through the sample in three dimensions, capturing spatial data to go along with the optical information.

The stage of [Zach]’s microscope is based on OpenFlexure’s Delta Stage, an open-source, 3D-printed delta-bot motion control platform that’s capable of positioning samples with sub-micron precision. Above the stage are the deceptively simple optics, with a laser diode light source, an objective lens, and a photodiode detector behind a pinhole. The detector feeds a homebrew trans-impedance amplifier that captures data at millions of points as the sample is moved through a small three-dimensional space. All that data gets crunched to find the Z-axis position corresponding to the maximum intensity at each point.

It takes a while to gather all this data — up to several days for even a small sample — but it works pretty well. [Zach] already has some ideas for reducing noise and speeding up the scan time; perhaps a stage based on DVD parts like this one would be faster than the delta stage. We look forward to seeing his improvements.

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Clay Pot MP3 Player Whipped Up With The Freedom-K64F

April 24, 2021 by Lewin Day 13 Comments

In the streaming era, few of us think about MP3s on a day to day basis anymore. Our music collection is managed by warring executives in streaming companies from far-off lands. However, for [vinod], they’re still useful — seeing as he just built himself an MP3 player that fits in a clay pot.

The build is based on the FRDMK64F development board, packing a powerful 120 MHz ARM chip. This has enough grunt to decode MP3s on the fly, using the Helix MP3 decoder library. The MP3s themselves are streamed off an SD card, using the faster SDIO access method rather than relying on slower SPI. Once decoded, the resulting PCM audio data is shifted out via a DAC using the chip’s DMA hardware, allowing for smooth, glitch-free playback. Output to a big woofer is via a 15 W class D amplifier, with the whole rig powered from a USB powerbank.

With all the electronics piled on the back of a big woofer speaker with lashings of hot glue, the final result is quite imposing; all the more so when installed neatly inside a clay pot acting as a bass reflex enclosure. We’ve seen some concrete cast speakers before, but not nearly enough hacker projects in clay. Please rectify this, and inform us once you’ve done so. Thanks in advance — video after the break!

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Modding A Hot Wheels Car Into A Radio Controlled Drift Weapon

April 23, 2021 by Lewin Day 14 Comments

Hot Wheels are some of the most popular diecast toy cars worldwide. The car bodies are faithful recreations of the real thing, though the models are mere stationary playthings. That wasn’t good enough for [Jakarta Diecast Project], who set about modifying a little BMW E30 M3 into an awesome radio-controlled drift car.

The build starts by disassembling the original car, and pulling out the original wheels. The baseplate is then modified to accept a new rear suspension and axle assembly. A small DC motor is mounted to the assembly to drive the rear wheels. A set of front steering knuckles are then installed up front, with their own suspension and hooked up to a tiny servo for steering. Everything’s controlled by a compact off-the-shelf RC receiver, which even features a gyro to help keep the tiny car straight under acceleration. The bodyshell is then stripped of paint, and given a sweet bodykit, before receiving a lurid orange paint job and decals. It’s reattached to the car’s baseplate via magnets, which make taking the car apart easy when service or modifications are required.

While the build doesn’t go into the nitty gritty on some of the harder parts, like the construction of the incredibly complex front knuckles, it’s nonetheless a great guide to building such a tiny and well-presented RC car. In looks and performance, the result trounces typical commercial offerings in the same scale, as you’d expect from such a hand-crafted masterpiece. It may not be the smallest RC car we’ve featured, but it is one of the coolest. Video after the break.

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Pi-Based Spectrometer Puts The Complexity In The Software

April 23, 2021 by Dan Maloney 43 Comments

Play around with optics long enough and sooner or later you’re probably going to want a spectrometer. Optical instruments are famously expensive, though, at least for high-quality units. But a useful spectrometer, like this DIY Raspberry Pi-based instrument, doesn’t necessarily have to break the bank.

This one comes to us by way of [Les Wright], whose homebrew laser builds we’ve been admiring for a while now. [Les] managed to keep the costs to a minimum here by keeping the optics super simple. The front end of the instrument is just a handheld diffraction-grating spectroscope, of the kind used in physics classrooms to demonstrate the spectral characteristics of different light sources. Turning it from a spectroscope to a spectrometer required a Raspberry Pi and a camera; mounted to a lens and positioned to see the spectrum created by the diffraction grating, the camera sends data to the Pi, where a Python program does the business of converting the spectrum to data. [Les]’s software is simple by complete, giving a graphical representation of the spectral data it sees. The video below shows the build process and what’s involved in calibrating the spectrometer, plus some of the more interesting spectra one can easily explore.

We appreciate the simplicity and the utility of this design, as well as its adaptability. Rather than using machined aluminum, the spectroscope holder and Pi cam bracket could easily be 3D-printer, and we could also see how the software could be adapted to use a PC and webcam.

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