Author: Al Williams

4351 Articles

Upcycled Dryer Motor Makes Budget Disk Sander

September 21, 2020 by 39 Comments

At the most basic level, most shop tools are just a motor with the right attachments. But the details are often far from simple. [DuctTapeMechanic] took a junker clothes dryer, yanked the electric motor from it, and converted it into a disk sander. The price was right at about $10. You can see it all after the break.

As you might imagine, having the motor is only half the battle. You also need a way to mount the thing securely and a way to affix the sanding disk. While this doesn’t pose the same challenges as, say, a drill press, it does take some thought. The motor in the donor dryer didn’t have threads on the shaft, so a bolt and some welding time took care of that. We suspect that’s tricky because you need the shaft and the bolt to be concentric and level.

Once you have a threaded shaft, the rest of the build is anti-climatic. A little carpentry and a little electrical. We would probably cover up the electrical connections a bit more. It seems like you’d want to know which way the motor spins so you could use a reverse thread, if necessary. From the video, we think the motor he has was spinning the right way, but we don’t know if that’s always true.

There’s something satisfying about building your own tools. If you work on smaller things, we’ve seen a miniature sander that might be handy to have around. If you want to go the other way, try finding an old floor polisher instead of a dryer.

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Linux Fu: Simple SSH File Sharing

September 21, 2020 by 28 Comments

If you have more than one Linux computer, you probably use ssh all the time. It is a great tool, but I’ve always found one thing about it strange. Despite having file transfer capabilities in the form of scp and sftp, there is no way to move a file back or forth between the local and remote hosts without starting a new program on the local machine or logging in from the remote machine back to the local machine.

That last bit is a real problem since you often access a server from behind a firewall or a NAT router with an ephemeral IP address, so it can’t reconnect to you anyway. It would be nice to hit the escape character, select a local or remote file, and teleport it across the  interface, all from inside a single ssh session.

I didn’t quite get to that goal, but I did get pretty close. I’ll show you a script that can automatically mount a remote directory on the local machine. You’ll need sshfs on the local machine, but no changes on the remote machine where you may not be able to install software. With a little more work, and if your client has an ssh server running, you can mount a local directory on the remote machine, too. You won’t need to worry about your IP address or port blocking. If you can log into the remote machine, you are good.

Combined, this got me me very close to my goal. I can be working in a shell on either side and have access to read or write files on the other side. I just have to set it up carefully. Continue reading “Linux Fu: Simple SSH File Sharing” →

TI And Cadence Make PSpice Free

September 20, 2020 by 29 Comments

We like simulation software. Texas Instruments long offered TINA, but recently they’ve joined with Cadence to make OrCAD PSpice available for free with some restrictions. You’ve probably heard of PSpice — it’s widely used in academia and industry, but is usually quite costly. You can see a promotional overview video below.

The program requires registration and an approval step to get a license key. The downloaded program has TI models along with other standard models. There seem to be few limits as long as you stick to the supplied library. According to the datasheet, there are no size or simulation complexity limitations in that case. If you want to use other models, you can, but that’s where the limitations hit you:

There is no limitation of how many 3rd party models can be imported into the design. However, if 3rd party models are imported, a user will be able to plot a maximum of 3 signals at a time of their choice when any 3rd party model is imported from web.

We aren’t completely sure what “from web” means there, but presumably they just mean from other sources. In any event, you still get AC, DC, and transient analysis with plenty of options like worst-case timing analysis. Mixed signal designs are supported and there is a wealth of data plotting options, as you would expect.

This is a great opportunity to drive some serious software that is widely used in the industry. The only thing that bummed us out? It runs under Windows. We couldn’t get it to work under Wine, but a Windows 10 VM handled it fine, although we really hate running a VM if we don’t have to.

Still, the price is right and it is a great piece of software. We also liked the recent Micro-Cap 12 release, but we don’t expect any updates for that. Of course, LTSpice is quite capable, too.

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A Big Computer Needs A Big Keyboard

September 19, 2020 by 36 Comments

It seems like many keyboard aficionados have been gravitating towards ever smaller boards, but not [Ren]. He’s mostly completed a 433% keyboard with a whopping 450 distinct keys. Using two off the shelf PCBs and Teensy to control it all, this keyboard means you’ll never need to strain to make some awkward chord.

The PCBs have a diode matrix arrangement for 225 keys, which we would have thought was big enough. After all, a Scrabble board has 225 squares, so we assume that’s why the vendor calls them scrabbleboards. Honestly, we’re jealous someone has the desk space for this monster. We were also thinking what other sorts of switch-like sensors you could use with this board. Imagine a home system, for example, with 225 occupancy sensors, each with its own key you could easily read via USB.

There was a time when building your own keyboard of any sort would have been challenging. But now there’s a cottage industry supplying chips, switches, caps, and PCBs to those looking to craft their own custom input devices. The ready availability of 3D printers has also sparked a minor revolution in custom keyboard enclosures and keycaps.

If you’re a fan of the tiny keyboards, we’ve seen some impressive specimens that might catch your fancy. If nothing else, at least they require less soldering. Especially when they only have seven keys.

Thanks [ptkwilliams] for the tip!

Parsing Math In Python

September 18, 2020 by 10 Comments

Programming computers used to be harder. Don’t get us wrong — today, people tend to solve harder problems with computers, but the fundamental act of programming is easier. We have high-level languages, toolkits, and even help from our operating systems. Most people never have to figure out how to directly read from a disk drive, deblock the data into records, and perform multiplication using nothing but shifts and adds. While that’s a good thing, sometimes it is good to study the basics. That was [gnebehay’s] thought when his university studies were too high level, so he decided to write an arithmetic expression parser in Python. It came out in about 100 lines of code.

Interpreting math expressions is one of those things that seems simple until you get into it. The first problem is correctly lexing the input — a term that means splitting into tokens. For a human, it seems simple that 5-3 is three tokens, {5, -, and 3} and that’s easy to figure out. But what about 5+-3? That’s also three tokens: {5,+,-3}. Tricky.

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Figuro Draws 3D In Browser

September 17, 2020 by 11 Comments

We would have never guessed there would be so many browser-based CAD packages. While TinkerCAD is great for simple things, there are also packages such as OnShape that rival commercial CAD programs. A site calle Figuro claims to occupy the space between TinkerCAD and Blender. We aren’t so sure, but it is an interesting entry into the field. Apparently, Figuro has been around for some time, but has recently had a major face lift. The new interface looks good, but it has invalidated a number of video tutorials on their YouTube channel.

One of the things we like about TinkerCAD is it is highly discoverable. That is, you can fire it up, play with it a bit, and probably do quite a few things. Maybe it is just us, but Figuro didn’t give us the same experience. It is easy enough to draw simple shapes. But trying to multiselect was unreliable. Panning and rotating the view was very sensitive too, so we found we were occasionally lost in the work view with no easy way to reset the view. Even something as simple as subtracting one shape from another was painful.

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TOBOT Is Your Tic Tac Toe Opponent With A Bad Attitude

September 16, 2020 by 4 Comments

[3dprintedlife] is apparently a little bored. Instead of whiling away the time playing tic tac toe, he built an impressive tic tac toe robot named TOBOT. The robot uses a Rasberry Pi Zero and a Feather to control a two-axis robot arm that can draw the board and make moves using a pen. It also uses a simple computer vision system to look at the board to understand your move, and it has a voice too.

The other thing TOBOT has is a bad attitude. The robot wants to win. Badly. Check out the video below and you’ll see what we mean.

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