Making Custom Curved Mirrors At Home

July 16, 2021 by Tom Nardi 8 Comments

Generally speaking, creating custom mirrors is a complex task that involves a lot of careful grinding, and isn’t something to be taken lightly if you need precision results. Just ask the folks who provided NASA with a wonky mirror for the Hubble. But assuming you’re not working on an orbital space telescope (or even a ground based one, for that matter), [volzo] has recently documented some techniques for producing single and double curved mirrors of reasonable quality using common workshop tools.

The first step is finding something that’s a bit easier to work with than glass. After testing various reflective materials such as PVC foil and painted PETG sheets by comparing the reflections of projected test patterns, [volzo] found that laminated polystyrene gave the most accurate results. If you just want to make a simple bent mirror, he shows how you can pop one of these sheets on a CNC router, make the appropriate cuts, and fold them into shape.

That part might seem a bit obvious, but what about a more complex shape? Here, [volzo] points to how the thin sheets of polystyrene also lend themselves to vacuum forming. As demonstrated in the video below, all it takes is a 3D printed plug and some basic equipment to rapidly produce mirrors in arbitrary shapes.

Now obviously the optical properties of such mirrors will leave something to be desired, but depending on your application, that might not be such a big deal. As examples [volzo] shows off a few projects using these custom mirrors, such as a tabletop camera that captures both sides of the table simultaneously and a circular projector. Laminated polystyrene could potentially even be used to create low-cost variable mirrors.

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Will We Soon Be Running Linux On SiFive Cores Made By Intel?

June 25, 2021 by Jenny List 38 Comments

There’s an understandably high level of interest in RISC-V processors among our community, but while we’ve devoured the various microcontroller offerings containing the open-source core it’s fair to say we’re still waiting on the promise of more capable hardware for anything like an affordable price. This could however change, as the last week or so has seen a flurry of interest surrounding SiFive, the fabless semiconductor company that has pioneered RISC-V technology. Amid speculation of a $2 billion buyout offer from the chip giant Intel it has been revealed that the company best known for the x86 line of processors has licensed the SiFive portfolio for its 7nm process. This includes their latest and fastest P550 64-bit core, bringing forward the prospect of readily available high-power RISC-V computing. Your GNU/Linux box could soon have a processor implementing an open-source ISA, without compromising too much on speed and, we hope, price.

All this sounds pretty rosy, but there is of course a downer for open-source hardware enthusiasts. These chips may rely on some open-source technologies, but sadly they will not themselves be open-source chips as there will be plenty of proprietary IP contained within them. We can thus only hope that Intel see fit to provide the same level of Linux support for them as they do for their x86 ranges, and we’re not left in the same situation with respect to ongoing support as we are with so many other chips. Meanwhile it’s worth remembering that SiFive are not the only player in the world of RISC-V cores, so it’s likely that competitors to the P550 and its stablemates will not be far behind.

If you’d like a more in-depth explanation of the true open-source nature of a RISC-V chip, we’ve featured something on that theme before.

Header image: Gareth Halfacree, CC BY-SA 2.0.

3D Printed Mecanum Wheels For Hoverboard Motors

June 25, 2021 by Tom Nardi 9 Comments

At this point, somebody taking the motors out of a cheap “hoverboard” and using them to power a scooter or remote controlled vehicle isn’t exactly a new idea. But in the case of the FPV rover [Proto G] has been working on, his choice of motors is only part of the story. The real interesting bit is the 3D printed omnidirectional Mecanum wheels he’s designed to fit the motors, which he thinks could have far reaching applications beyond his own project.

Now, that isn’t to say that the rover itself isn’t impressive. All of the laser cutting and sheet metal bending was done personally by [Proto G], and we love the elevated GoPro “turret” in the front that lets him look around while remotely driving the vehicle. Powered by a pair of Makita cordless tool batteries and utilizing hobby-grade RC parts, the rover looks like it would be a fantastic robotic platform to base further development on.

The Mecanum wheels themselves are two pieces, and make use of rollers pulled from far smaller commercially available wheels. This is perhaps not the most cost effective approach, but compared to the alternative of trying to print all the rollers, we see the advantage of using something off-the-shelf. If you’re not sure how to make these weird wheels work for you, [Proto G] has also released a video explaining how he mixes the RC channels to get the desired omnidirectional movement from the vehicle.

If you’re content with more traditional wheeled locomotion, we’ve previously seen how quickly a couple of second-hand hoverboards can be turned into a impressively powerful mobile platform for whatever diabolical plans you may have.

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New Part Day: RP2040 Chips In Single Unit Quantities

June 1, 2021 by Jenny List 27 Comments

Since the launch of the Raspberry Pi Pico back in January the little board with its newly-designed RP2040 microcontroller has really caught the imagination of makers everywhere, and we have seen an extremely impressive array of projects using it. So far the RP2040 has only been available on a ready-made PCB module, but we have news today direct from Eben Upton himself that with around 600k units already shipped, single-unit sales of the chip are commencing via the network of Raspberry Pi Approved Resellers.

This news will doubtless result in a fresh explosion of clever projects using the chip, but perhaps more intriguingly it will inevitably result in its appearance at the heart of a new crop of niche products that go beyond simple clones of the Pico in different form factors. The special ingredient of those two PIO programmable state machines to take the load of repetitive tasks away from the cores raises it above being merely yet another microcontroller chip, and we look forward to that feature being at their heart.

The Broadcom systems-on-chip that power Raspberry Pi’s existing range of Linux-capable boards have famously remained unavailable on their own, meaning that this move to being a chip vendor breaks further new ground for the Cambridge-based company. It’s best not to think of it in terms of their entering into competition with the giants of the microcontroller market though, because a relative minnow such as the RP2040 will be of little immediate concern to the likes of Microchip, ST, or TI. A better comparison when evaluating the RP2040’s chances in the market is probably Parallax with their Propeller chip, in that here is a company with a very solid existing presence in the education and maker markets seeking to capitalise on that experience by providing a microcontroller with that niche in mind. We look forward to seeing where this will take them, and we’d hope to eventually see a family of RP2040-like chips with different package and on-board peripheral options.

New Part Day: ESP32-WROOM-DA

May 21, 2021 by Jenny List 38 Comments

We’re always interested in the latest from the world’s semiconductor industry here at Hackaday, but you might be forgiven for noticing something a little familiar about today’s offering from Espressif. The ESP32-WROOM-DA has more than a passing resemblance to the ESP32-WROOM dual-core-microcontroller-with-WiFi module that we’ve seen on so many projects over the last few years because it’s a WROOM, but this one comes with a nifty trick to deliver better WiFi connectivity.

The clever WiFi trick comes in the form of a pair of antennas at 90 degrees to each other. It’s a miniaturised version of the arrangement with which you might be familiar from home routers, allowing the device to select whichever antenna gives the best signal at any one time.

We can see that the larger antenna footprint will require some thought in PCB design, but otherwise the module has the same pinout as the existing WROVER. It’s not much of a stretch to imagine it nestled in the corner of a board at 45 degrees, and we’re sure that we’ll see it appearing in projects directly. Anything that enhances the connectivity of what has become the go-to wireless microcontroller on these pages can only be a good thing.

Shop Exhaust Fan Salvaged From Broken Microwave

May 20, 2021 by Tom Nardi 7 Comments

You don’t have to look hard to find a broken microwave. These ubiquitous kitchen appliances are so cheap that getting them repaired doesn’t make economical sense for most consumers, making them a common sight on trash day. But is it worth picking one of them up?

The [DuctTape Mechanic] certainly thinks so. In his latest video, he shows how the exhaust fan from a dead microwave can easily and cheaply be adapted to blow smoke and fumes out of your workshop. While it’s obviously not going to move as much air as some of the massive shop fans we’ve covered over the years, if you’re working in a small space like he is, it’s certainly enough to keep the nasty stuff moving in the right direction. Plus as an added bonus, it’s relatively quiet.

Now as you might expect the exact internal components of microwave ovens vary wildly, so there’s no guarantee your curbside score is going to have the same fan as this one. But the [DuctTape Mechanic] tries to give a relatively high-level overview of how to liberate the fan, interpret the circuit diagram on the label, and wire it up so you can plug it into the wall and control it with a simple switch. Similarly, how you actually mount the fan in your shop is probably going to be different, though we did particularly like how he attached his to the window using a pair of alligator clips cut from a frayed jumper cable.

Got a donor microwave but not in the market for a impromptu shop fan? No worries. We recently saw a dud microwave reborn as a professional looking UV curing chamber that would be the perfect partner for your resin 3D printer. Or perhaps you’d rather turn it into a desktop furnace capable of melting aluminum, copper, or bronze.

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Practical Sensors: The Hall Effect

May 20, 2021 by Al Williams 22 Comments

Measuring a magnetic field can be very easy with some pretty low tech, or it can be very high tech. It just depends on what kind of measurement you need and how much effort you want to expend. The very simplest magnetic sensors are reed switches. These are basically relays with no coil. Instead of a coil, an external magnet gets close enough to make or break the contacts in the reed. You see these a lot in, for example, door alarm sensors.

Then again, there’s no real finesse to a reed. It changes state when it sees enough of a magnetic field and that’s about all. You could use a compass with some sort of detection on the needle to get some more information about the field, but not much more. That was, however, how early magnetometers worked. Today, you have lots of options, including the nearly ubiquitous Hall effect sensor.

You might use a Hall effect to measure the magnetic button on a keyboard key coming down when you press it or the open and closed state of a valve. A lot of Hall effects see service as current monitors. Since a coil generates a magnetic field proportional to the current through it, a magnetic sensor can estimate the current in a coil of wire without any physical contact. Hall effects can also watch a magnet go by in a linear motion system or a rotating system to get an idea of position or speed. For example, check out this brushless motor controller that uses three sensors to understand the motor’s position.

History

Edwin Hall identified the effect in 1879. The basic idea is simple: an electrical conductor carrying current will exhibit changes due to an external magnetic field nearby. These changes show up as voltage you measure across the conductor. Normally, the voltage across a conductor will be nearly zero, but with a magnetic field, you’ll get a non-zero reading in proportion to the magnetic field strength in a particular plane, as we’ll see shortly.

Hall effect sensors are just one type of modern magnetometer. There are many different kinds including those that use inductive pickup coils that may or may not rotate or a fluxgate, which is a special type of coil. Some use a scale or a spring to measure force against another magnet — sometimes microscopically. You can even detect a magnetic field using optical properties like the Kerr effect or Faraday rotation.

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