Frequency Tells Absolute Temperature

January 18, 2023 by 21 Comments

It is no secret that semiconductor junctions change their behavior with temperature, and you can use this fact to make a temperature sensor. The problem is that you have to calibrate each device for any particular transistor you want to use as a sensor, even if they have the same part number. Back in 2011  1991, the famous [Jim Williams] noted that while the voltage wasn’t known, the difference between two readings at different current levels would track with temperature in a known way. He exploited this in an application note and, recently, [Stephen Woodward] used the same principle in an oscillator that can read the temperature.

The circuit uses an integrator and a comparator. A FET switches between two values of collector current. A comparator drives the FET and also serves as the output.  Rather than try to puzzle out the circuit just from the schematic, you can easily simulate it with LT Spice or Falstad. The Falstad simulator doesn’t have a way to change the temperature, but you can see it operating. The model isn’t good enough to really read a temperature, but you can see how the oscillation works

You can think of this as a temperature-to-frequency converter. It would be easy to read with, say, a microcontroller and convert the period to temperature.  Every 10 microseconds is equal to a degree Kelvin. Not bad for something you don’t have to calibrate.

Thermistors are another way to measure temperature. Sometimes, you don’t need a sensor at all.

Retro Gadgets: Tired Of The Beatles On 8 Track? Try The Police

January 18, 2023 by 48 Comments

In the 1970s, 8-track audio players were very popular, especially in cars. For a couple of bucks, you could have the latest album, and you didn’t have to flip the tape in the middle of a drive like you did with a cassette. We’ve seen plenty of 8-tracks and most of us a certain age have even owned a few players. But we couldn’t find anyone who would admit to owning the Bearcat 8 Track Scanner, as seen in the 1979 Popular Electronics ad below.

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3D Printing Giant LEGO-Like Blocks To Build Big Toys

January 18, 2023 by 21 Comments

[Ivan Miranda] is all about big 3D prints. He’s now set about printing giant blocks in the vein of LEGO Technic to build himself a full-sized rideable go kart. The project is still in progress, but [Ivan] has made great progress with his design.

The benefit of 3D printing giant blocks like this is that they open up the possibilities for rapid prototyping of big projects. It’s already easy to snap together a little LEGO tank, boat, or car at the small scale. Bigger blocks would make that possible for larger builds, too. Plus, once you’ve got plenty of blocks, there’s no need to wait for the 3D printer to churn out parts. You can just play with your toolbox of existing components.

[Ivan]’s design has faced some teething problems along the way. He struggled to solve various coupling problems for joining the blocks in various orientations, and made iterative changes to solve the issue. Eventually, he realized if he just eliminated an offset between the top and side holes of his beam design, everything would neatly work out. Plus, he learned that he could print a tiny scale version of his big blocks in order to test out designs without using as much plastic.

We love the idea of having a garage full of adult-sized LEGO-style blocks for big projects. The only caveat is that you really need a giant printer like [Ivan’s] to make them. Continue reading “3D Printing Giant LEGO-Like Blocks To Build Big Toys” →

Punycodes Explained

January 18, 2023 by 18 Comments

When you’re restricted to ASCII, how can you represent more complex things like emojis or non-Latin characters? One answer is Punycode, which is a way to represent Unicode characters in ASCII. However, while you could technically encode the raw bits of Unicode into characters, like Base64, there’s a snag. The Domain Name System (DNS) generally requires that hostnames are case-insensitive, so whether you type in HACKADAY.com, HackADay.com, or just hackaday.com, it all goes to the same place.

[A. Costello] at the University of California, Berkley proposed the idea of Punycode in RFC 3492 in March 2003. It outlines a simple algorithm where all regular ASCII characters are pulled out and stuck on one side with a separator in between, in this case, a hyphen. Then the Unicode characters are encoded and stuck on the end of the string.

First, the numeric codepoint and position in the string are multiplied together. Then the number is encoded as a Base-36 (a-z and 0-9) variable-length integer. For example, a greeting and the Greek for thanks, “Hey, ευχαριστώ” becomes “Hey, -mxahn5algcq2″. Similarly, the beautiful city of München becomes mnchen-3ya. Continue reading “Punycodes Explained” →

Spray-On Keyboard Is As Light As It Gets

January 18, 2023 by 19 Comments

We’ve all seen those ‘nothing’ keyboards, where the keys themselves are not much more than projected lasers, and users are asked to ritually beat their poor fingertips into the table — which has little give and even less clack. Well, a team at the Korea Advanced Institute of Science and Technology have come up with a way to eschew the keyboard altogether.

Essentially, the user wears a thin, breathable mesh of silver nanowires coated in gold, which is then embedded in a polyurethane coating. The mesh is sprayed onto their forearms and hands on the spot, and the mesh terminates in a small enclosure that is also worn on the skin. This contains a small Bluetooth unit that beams data back to a computer, a machine, or potentially another user wearing the same type of unit.

As the skin stretches and contorts, the mesh senses small electrical changes within. These changes become meaningful with applied AI, which maps the changes to specific gestures and manual tasks. To do this, the team started with teaching it to distinguish between patterns from tasks like typing on a phone, typing on a regular keyboard, and then holding and interacting with six differently-shaped simple objects.

The team isn’t stopping there — they plan to try capturing a larger range of motion by using the nanomesh on multiple fingers. In addition to facilitating communication between humans and machines, this could leave a huge fingerprint on gaming and VR.

Grass Gauge Tells You When The Lawnmower’s Catcher Is Full

January 18, 2023 by 20 Comments

If you’re not mowing your lawn regularly, you’re probably familiar with the hassle of overfilling your catcher. Grass clippings end up scattered everywhere, and you end up with a messy yard after all your hard work. [Dominic Bender] designed a mower fill gauge to eliminate this problem which shows you when your catcher is getting full.

The concept behind the gauge’s operation is simple. Catcher-based mowers rely on airflow from the spinning blades to carry grass into the catcher. That airflow is, in this case, also used to push up a flap mounted in the top of the catcher. As the catcher fills with grass, that airflow no longer reaches the flap, which sinks down, indicating the catcher is getting full. The basic design is a simple 3D printed flap and housing that uses a short piece of filament as a hinge. There’s also a small mesh guard to stop the flap getting clogged by the incoming grass clippings.

If you’re the forgetful sort, or your enthusiastic children aren’t always emptying the catcher when they should, this gauge might be a useful tool for you. Alternatively, consider robotizing your mowing in the vein of other builds we’ve seen, including one by yours truly. If you’ve got your own nifty gardening hacks, be sure to drop us a line!

One-Size-Fits-All Wrench Points To A Nut Job

January 17, 2023 by 37 Comments

When [Hand Tool Rescue] came across a 1919 patent for a one size fits all wrench, he couldn’t help but recreate it. Described in the patent as “a new, original, ornamental design for a wrench”, the wrench had a slot for possibly every fastener that the inventor could think of. Not only did it have slots for several hexagonal fasteners, but many others for octagonal, square and even a pentagonal fastener.

[Hand Tool Rescue] reckons there are 47 slots for various sizes and types of fasteners, not counting the ones whose purpose he could not fathom. Just in case he missed any fastener sizes, the original designer decided to add an alligator wrench at the other end of the handle, potentially negating the need for any of the other slots. The tool even features a sharp edge along one of the sides, possibly for use as a scraper of some kind.

Why such a crazy design was patented, or what were the functions of some of its slots are questions that will likely remain unanswered. At best, we can all take guesses at solving the mystery of this tool. [Hand Tool Rescue] scales the original drawing such that one of the slots has a width of 1 inch, and then uses that as a template to recreate the wrench. He starts with a slab of 3/8th inch thick, grade 4140 steel, which has a high strength to weight ratio and can be case hardened after machining, making it suitable for this ornamental project.

He then embarks on his journey of excessive milling, drilling, filing, band sawing and shaping (using a slotting attachment), totaling about 11 hours worth of drudgery. Of course, one could argue that it would have been much easier, and accurate, to have used modern machining methods. And we are spoilt for choices here among laser cutting, water jet cutting or even EDM machining, any of which would have done the job faster, cleaner and more precisely. But we guess [Hand Tool Rescue] wanted to stick to traditional methods as would have been available in 1919 to an inventor who wanted to make a prototype of his awesome, all in one wrench.

If you can help explain the overall function of this wrench, or identify some of the more vague slots in it, then [Hand Tool Rescue] would be happy to get the feedback. And talking about less desirable wrenches, check out how this Sliding Wrench Leaves a Little to be Desired.

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