Author: Al Williams

4505 Articles

A Magnetron Tear Down

December 5, 2019 by 28 Comments

Microwave ovens are everywhere, and at the heart of them is a magnetron — a device that creates microwaves. [DiodeGoneWild] tore one apart to show us what was inside and how it works. If you decide to do this yourself, be careful. The magnetron may have insulators made of beryllium oxide and inhaling dust from the insulator even one time can cause an incurable lung condition.

Luckily, you can’t get a lung problem from watching a video. In addition to just seeing the guts of the magnetron, there are also explanations about how everything works with some quick sketches to illustrate the points.

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FreeCAD TechDraw Workbench Tutorial

December 3, 2019 by 33 Comments

FreeCAD started out a little shaky, but it has gotten better and better. If you are trying to draw a schematic, it probably isn’t the best way to do it. However, it is a great graphical alternative to OpenSCAD for 3D printing and even incorporates OpenSCAD if you don’t want to choose. However, if you have a 3D part — regardless of how you want to create it in real life — having a proper mechanical drawing is very valuable. FreeCAD’s TechDraw workbench makes this very easy and [Joko] has a tutorial that shows exactly how to do it.

Machinists everywhere are used to looking at these drawings that typically show a top view, a front view, and a side view. The program will automatically project the views you select and then allows you to pick dimensions. It creates them and keeps them up to date if you change them in the model later.

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Almond: Open Personal Assistant From Stanford

December 1, 2019 by 19 Comments

The current state of virtual personal assistants — Alexa, Cortana, Google, and Siri — leaves something to be desired. The speech recognition is mostly pretty good. However, customization options are very limited. Beyond that, many people are worried about the privacy of their data when using one of these assistants. Stanford Open Virtual Assistant Lab has rolled out Almond, which is open and is reported to have better privacy features.

Like most other virtual assistants, Almond has skills that determine what it can do. You can use Almond in a browser, on a Google phone, or as a command line application. It all lives on GitHub, so if you don’t like something you are free to fix it.

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Manual Mesh Bed Levelling For 3D Printers

December 1, 2019 by 18 Comments

In 3D printing, we often talk about leveling the print bed, although that’s not an accurate term. A bed that is level in our terms presents a flat surface that is parallel to the path of the print head, but within reason we care little about that. Instead we care more about it being parallel to the path of the head than it being perfectly flat. If we had a perfectly flat bed — say a sheet of glass — you’d think it might be pretty easy, but for some other materials it could be convex or concave or even have ripples all over the place. [Teaching Tech] shows you how to manually “level” the bed using a mesh but without using an automatic sensor. You can see the technique in the video below.

When you use adjustments to level the bed, you are tramming it, but only the very pedantic use that term for fine adjustment. But no amount of adjusting bed springs will get rid of bulges and ripples. A common solution is to use a sensor to measure the distance to the bed and form a mesh correction. Then, as the printer head moves in the XY plane, the software will adjust the Z-axis to rise over bumps and go down if there is a concave portion of the bed. What [Teaching Tech] is doing, however, is a manual mapping. You won’t need to add a sensor to your printer to take advantage of the method. 

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DeepPCB Routes Your KiCAD PCBs

December 1, 2019 by 36 Comments

Computers can write poetry, even if they can’t necessarily write good poetry. The same can be said of routing PC boards. Computers can do it, but can they do it well? Of course, there are multiple tools each with pluses and minuses. However, a slick web page recently announced deeppcb.ai — a cloud-based AI router — and although details are sparse, there are a few interesting things about the product.

First, it supports KiCAD. You provide a DSN file, and within 24 hours you get a routed SES file. Maybe. You get three or four free boards –apparently each week — after which there is some undisclosed fee. Should you just want to try it out, create an account (which is quick and free — just verify your e-mail and create a password). Then in the “Your Boards” section there are a few examples already worked out.

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Multi Material 3D Printing Makes Soft Robot

November 30, 2019 by 8 Comments

When you zoom in on a fractal you find it is made of more fractals. Perhaps that helped inspire the Harvard 3D printers that have various arrays of mixing nozzles. In the video below you can see some of the interesting things you can do with an array of mixing nozzles. The coolest, we think, is a little multi-legged robot that uses vacuum to ambulate across the bench. The paper, however, is behind a paywall.

There are really two ideas here. Mixing nozzles are nothing new. Usually, you use them to mimic a printer with two hot ends. That is, you print one material at a time and purge the old filament out when switching to the new filament. This is often simpler than using two heads because with a two head arrangement, both the heads have to be at the same height, you must know the precise offset between the heads, and you generally lose some print space since the right head can’t cross the left head and vice versa. Add more heads, and you multiply those problems. We’ve also seen mixing nozzles provide different colors.

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DSP Spreadsheet: Talking To Yourself Using IQ

November 29, 2019 by 12 Comments

We’ve done quite a bit with Google Sheets and signal processing: we’ve generated signals, created filters, and computed quadrature signals. We can pull all that together into an educational model for two SDRs talking to each other, but it’s going to require two parts: modulation and demodulation. Guess what? We can do that with a spreadsheet.

The first step is to generate a reference clock for the carrier. You’ll need a cosine wave (I) and sine wave (Q). Of course, you also need the time base. That’s columns A-C in the spreadsheet and works like other signal generation we’ve seen.

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