Improved Technique For Resistive Divider Keypads

June 9, 2021 by 22 Comments

[Lauri Pirttiaho] from the [Swiss Knife of Electronics] channel explains how to simplify your resistive divider keypad design on Hackaday.io.

The usual method involves building a resistive ladder that gives unique and equally spaced voltages for each keypress. If you have just four or five discrete buttons, it isn’t terribly difficult, but if you have a 12- or 16-keypad matrix, things get complicated. [Lauri] looked into the past to come up with a better way, specifically a 646 page, 1 kg textbook from 1990 — Analogue Ic Design: The Current-Mode Approach by Toumazou, Lidgey, and Haigh. He learned that sometimes what’s hard to do in the voltage domain is easy in the current domain.

Normally you’d throw in some resistors to form different voltage dividers depending on which key is pressed, and read the resulting voltage off of a voltage divider with an ADC. But that means using the voltage divider equation, and the difference in voltage between keys can get very small. Dropping the voltage divider and measuring the current through a current mirror generates a linear voltage across its output load resistor that can be easily read by your microprocessor. And [Lauri] has posted an example of just such a program on his GitHub repository for an Arduino.

Heavy analog electronics, for sure, but something to keep in mind if you’re reading more than 12 keys. Do you have any examples of solving problems by looking into old and/or less-common techniques? Let us know in the comments below.

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Historical Hackers: Ctesibius Tells Time

June 9, 2021 by 11 Comments

People are obsessed with the time and the weather. We’ve talked about the weather since we were all cave dwellers hunting with spears. But the time is a different matter. Sure, people always had the idea of the passage of time. The sun rising and setting gives a natural sense of days, but daylight and dark periods vary by the time of year and to get an accurate and linear representation of time turns out to be rather difficult. That is unless you are a Greek engineer living in Alexandria around 250 BC.

Legend has it that and engineer working in his father’s barbershop led him to discover not only the first working clock, but also the pipe organ, launching the field of pneumatics in the process. That engineer was named Ctesibius and while his story is mostly forgotten, it shows he has a place as a historical hacker.

You might think there were timekeeping devices before 250 BC, and that’s sort of true. However, the devices before Ctesibius had many limitations. For example, a sundial can tell time, but only if the sun is shining. At night or during a storm it is worthless.

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3D Printed Calipers Work Like Clockwork

June 9, 2021 by 31 Comments

Most of us use calipers when working with our 3D printers. Not [Albert]. He has a clockwork caliper design that he 3D printed. The STL is available for a few bucks, but you can see how it works in the video below. We don’t know how well it works, but we’ll stick with our digital calipers for now.

The digital readout on this caliper is more like a sophisticated watch. A window shows 10s of millimeters and two dials show the single digits and the number after the decimal point.

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What Is Ultra Wideband?

June 9, 2021 by 36 Comments

If you’ve been following the world of mobile phone technology of late, you may be aware that Apple’s latest IPhones and AirTag locator tags bring something new to that platform. Ultra wideband radios are the new hotness when it comes to cellphones, so just what are they and what’s in it for those of us who experiment with these things?

An Apple AirTag being paired with an iPhone. Swisshashtag, CC BY-SA 4.0.
An Apple AirTag being paired with an iPhone. Swisshashtag, CC BY-SA 4.0.

Ultra wideband in this context refers to radio signals with a very high bandwidth of over 500 MHz, and a very low overall power density spread over that  spectrum. Transmissions are encoded not by modulation of discrete-frequency carriers as they would be in a conventional radio system, but by the emission of wideband pulses of RF energy across that bandwidth.  It can exist across the same unlicensed spectrum as narrower bandwidth channelised services, and that huge bandwidth gives it an extremely high short-range data transfer bandwidth capability. The chipsets used by consumer devices use a range of UWB channels between about 3.5 and 6.5 GHz, which in radio terms is an immense quantity of spectrum. Continue reading “What Is Ultra Wideband?” →

Flat Transformer Gives This PCB Tesla Coil Some Kick

June 9, 2021 by 16 Comments

Arguably, the most tedious part of any Tesla coil build is winding the transformer. Getting that fine wire wound onto a suitable form, making everything neat, and making sure it’s electrically and mechanically sound can be tricky, and it’s a make-or-break proposition, both in terms of the function and the aesthetics of the final product. So this high-output printed circuit Tesla should take away some of that tedium and uncertainty.

Now, PCB coils are nothing new — we’ve seen plenty of examples used for everything from motors to speakers. We’ve even seen a few PCB Tesla coils, but as [Ray Ring] points out, these have mostly been lower-output coils that fail to bring the heat, as it were. His printed coil generates some pretty serious streamers — a foot long (30 cm) in some cases. The secondary of the coil has 6-mil traces spaced 6 mils apart, for a total of 240 turns. The primary is a single 240-mil trace on the other side of the board, and the whole thing is potted in a clear, two-part epoxy resin to prevent arcing. Driven by the non-resonant half-bridge driver living on the PCB below it, the coil can really pack a punch. A complete schematic and build info can be found in the link above, while the video below shows off just what it can do.

Honestly, for the amount of work the PCB coil saves, we’re tempted to give this a try. It might not have the classic good looks of a hand-wound coil, but it certainly gets the job done. Continue reading “Flat Transformer Gives This PCB Tesla Coil Some Kick” →

Old DSLR Lens Becomes Useful Soldering Magnifier

June 9, 2021 by 10 Comments

Soldering tiny stuff is hard, if not impossible, without some optical assistance. [Ad_w00000] was having just this problem, so built himself a soldering magnifier to help.

The magnifier uses a variety of components [Ad_w00000] had lying around. For the optical side of things, an old Canon DSLR zoom lens was pressed into service as the main magnifying element. The lens was then fitted with an old laptop webcam, which was glued into an old lens extender to avoid modifying the main lens itself. The webcam is hooked up to an Asus Tinkerboard fitted with a touchscreen display to show the images. The whole lens assembly is then fitted onto an old TV stand to enable it to sit far enough above the work surface to focus properly.

The build is a great example of building something useful out of whatever you have on hand. Sometimes, that’s cheaper and quicker than spending money and waiting for something to ship. It also has the bonus that you’ll learn useful skills along the way.

We’ve seen other great soldering hacks recently, too, like this gimbal to help steady hand tremors. If you’ve got your own coming together, be sure to let us know!

Nintendo DS Transformed Into Gameboy Macro

June 8, 2021 by 7 Comments

Nintendo’s Game Boy line were the world’s most popular handheld gaming systems, but did have their drawbacks. Most notably, the Game Boy didn’t receive a backlit color LCD until the Game Boy Advance SP launched in 2003. Of course, you can always build your own Game Boy that rectifies this and other shortcomings, and that’s what [JoshuaGuess] did with this Gameboy Macro build.

The build ends up like a bigger version of the Game Boy Micro, the final release in the Game Boy line.

The build is based around a Nintendo DS Lite, one of Nintendo’s later handhelds featuring dual screens. In this build, the top screen is removed and discarded entirely. The motherboard is then hacked with a resistor on some test points to allow it to still boot with the top missing. The shell of the bottom half is then cleverly modified with epoxy clay and paint in order to hide the original hinge and give a clean finished aesthetic.

The final result is essentially a larger version of the Game Boy Micro, the final handheld in the Game Boy line. It also has the benefit of a bigger, brighter screen compared to virtually any Game Boy ever made. The only thing to note is that the DS hardware can only play Game Boy Advance games, not the earlier 8-bit titles.

It’s a fun build, and one that goes to show you don’t have to throw a Raspberry Pi in everything to have a good time. That can be fun too, though. If you end up building the Game Boy Nano or Game Boy Giga, please let us know. Be sure to include measurements to indicate how it’s scaled in SI units relative to the Game Boy Micro itself.