Author: Al Williams

4510 Articles

Tech In Plain Sight: Tough As Nails

March 15, 2022 by 17 Comments

When you think of machines you see around you every day, you probably think about your car, computer, or household appliances. However, the world is full of simple machines. One simple machine in particular, the inclined plane, shows up a lot. For example, think of the humble nail. If you are a woodworker or even a homeowner you probably have bags of them. They certainly are all around you if you are indoors and maybe even if you are outdoors right now. Nails have been the fastener of choice for a very long time and they are a form of a wedge which is a type of inclined plane.

What else can you say about nails? Turns out, there is a lot to know. Like other fasteners, there are nails for very specific purposes. There are even nails with two heads and — no kidding — nails with two points. Exactly what kind of nail you need depends on what you are doing and what’s important to you.

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3D Printing Snap Fit Joints

March 14, 2022 by 10 Comments

Owning a 3D printer seems to progress through stages. You start printing simple shapes. Then you get serious about calibration and quality. Eventually, you move to trying to design and build practical things. To get practical, you often need to join parts together and that requires glue, fasteners, threaded inserts, and plastic welding. However, you can also make parts that fit together using friction and the springiness of plastic. For example, [Lucas Carolo] recently had a look at 3D printing snap-fit joints. These are commonly seen on the end of straps so that you can connect two ends together.

Of course, you can use them anywhere you need a secure connection. However, you might want to consider that since the jaws compress, there will be repeated stress on the part, so it might not be a good choice for items that you will frequently snap together. Also, brittle plastic such as PLA might not be the best choice of materials. There are several different kinds of joints. The cantilever version has a hook that bends into place and, as mentioned earlier, is common on luggage or backpack straps. The post offers tips on how to design a durable hook. In particular, the orientation of the hook during printing is critical because of the stress involved.

Another type of snap-fit joint is the kind you find on many snap electronic enclosures or things like pen caps. In these joints, a large bump (a boss) fits into a similar groove on the other part. The post has a little less information on these but does mention that you should form the bosses with a chamfer. If you want more details, the post links to a great guide and an enclosure tutorial that you should check out.

We’ve covered this topic before and have some other guides to check out. We’ve also seen some pretty innovative connecting methods.

Clock Testing Sans Oscilloscope?

March 11, 2022 by 18 Comments

Like many people who repair stuff, [Learn Electronics Repair] has an oscilloscope. But after using it to test a motherboard crystal oscillator, he started thinking about how people who don’t own a scope might do the same kind of test. He picked up a frequency counter/crystal tester kit that was quite inexpensive — under $10. He built it, and then tried it to see how well it would work in-circuit.

The kit has an unusual use of 7-segment displays to sort-of display words for menus. There is a socket to plug in a crystal for testing, but that won’t work for the intended application. He made a small extender to simplify connecting crystals even if they are surface mount. He eventually added a BNC socket to the counter input, but at first just wired some test leads directly in.

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Is Your Tape Dispenser Radioactive?

March 11, 2022 by 26 Comments

Do you have anything radioactive in your house? Most people will say no, but they are probably wrong. A host of things ranging from glow-in-the dark timepieces to smoke detectors have some amount of radioactivity. But as [Wheeler Scientific] points out, so do some old Scotch tape dispensers. You can watch the video, below.

The dispenser in question is the C-15 which was very common around offices, military bases, and homes for years. They were made up until the 1980s. You have to wonder why a tape dispenser would be radioactive, and [Wheeler] has the explanation.

When you pull tape from the dispenser, you don’t want the dispenser to slide around the desk, so it needs to be heavy. But no one wants to have a giant dispenser nor do you want to pay for one made from a dense metal. So the plastic dispenser contains a ballast to make it heavier. In the case of the C-15 that ballast is thorium-containing monazite sand. A vintage counter shows the radioactivity which isn’t much, of course, but still way less than the ordinary sand used in newer models. You can also see in the video that the material is paramagnetic.

Monazite used to be a primary source of lanthanides but getting rid of the thorium led to alternate sources in the 1960s although it is still used as an ore for thorium. We know some lenses are radioactive. If you want to search your home for radioactivity and you don’t have a Geiger counter, you don’t need much to build one.

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Short Circuit Tracer For A Buck

March 10, 2022 by 22 Comments

Almost every meter you find today will have a continuity tester. Connect the probes and it will beep if there is a short and won’t if there isn’t. But where is the short? That’s another problem when trying to measure a component that is connected to many other components. [Learn Electronics Repair] wanted to have a tool to find shorts on a board and wanted to build a tester that uses 4-wire resistance measurement to isolate the device under test without having to do surgery on the circuit. His $1 build appears in the video below.

The first part of the video talks about the theory behind resistance measurement with two and four wires. Let shows several diagrams, but he mentions that at one point he shows an incorrect schematic (at 12:03) instead of the early correct one (at 10:35) and mentions it, but if you are skimming the video, you might get confused.

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Fumik: An Arduino Wall Drawing Robot Jellyfish

March 10, 2022 by 16 Comments

If you’ve ever wanted to build a large format plotter but didn’t have the floor space, maybe put it up against the wall and make it cute. That’s the idea behind Fumik, the wall-drawing robot. As you might expect, the little device is just a motion base with a pen. We hope there’s paper against the wall since not everyone wants computer-generated art on their drywall.

The maximum size is apparently 5 m wide by 3 m tall, plenty of room to express yourself. The controller is an Arduino Mega, and stepper motors with a CNC shield drive the whole assembly. Interestingly, the motor and electronics are all onboard the jellyfish itself, rather than the wall.

The device only holds one pen at a time, but you can draw with one color and then manually change the pen. The files on GitHub are good, but you’ll need to intuit some of the mechanics from the videos. However, since it uses off-the-shelf hardware, it should be pretty easy to figure it out. This looks like a cheap and cheerful wall plotter, and the results speak for themselves.

We have seen similar wall plotters. More than once, even.

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Reflow Hotplate Teardown Uncovers The Bare Minimum

March 10, 2022 by 13 Comments

[EEforEveryone] is trying to find a good hot plate for reflow soldering. After trying one cheap unit, he got another one. He was a bit underwhelmed. The grounding was suspect and the bed wasn’t totally flat. He tore it apart and was surprised that there was very little inside. While the construction wasn’t perfect, it was better than the previous unit. You can see a video of the teardown and review below.

Before powering it up, the first order of business was to rewire the ground system. After that, it was time to try it. However, by confusing Fahrenheit and Centigrade, he set the temperature much higher than necessary which creating a little smoke. Fixing the temperature helped, but there was still a bit of a smoky smell that eventually subsided.

The verdict? The hot plate worked well enough, but you probably do want to check the ground wiring before using it. That’s often a good idea where cheap equipment is concerned, anyway. But the real takeaway is that it looks like you could homebrew something equivalent without much trouble. The controller is an off-the-shelf module. A switch and a plug aren’t hard to figure out. The heating element could be a silicone heater or PCB heater meant for a 3D printer.

Of course, there are other options. You could use a wok. Or why not a waffle iron? You can also make a custom PCB.

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