Reverse Time Back To The Days Of RPN

September 26, 2024 by Bryan Cockfield 68 Comments

While Texas Instruments maintains dominance in the calculator market (especially graphing calculators), there was a time when this wasn’t the case. HP famously built the first portable scientific calculator, the HP-35, although its reverse-Polish notation (RPN) might be a bit of a head-scratcher to those of us who came up in the TI world of the last three or four decades. Part of the reason TI is so dominant now is because they were the first to popularize infix notation, making the math on the calculator look much more like the math written on the page, especially when compared to the RPN used by HP calculators. But if you want to step into a time machine and see what that world was like without having to find a working HP-35, take a look at [Jeroen]’s DIY RPN calculator.

Since the calculator is going to be RPN-based, it needs to have a classic feel. For that, mechanical keyboard keys are used for the calculator buttons with a custom case to hold it all together. It uses two rows of seven-segment displays to show the current operation and the results. Programming the Arduino Nano to work as an RPN calculator involved a few tricks, though. [Jeroen] wanted a backspace button, but this disrupts the way that the Arduino handles the input and shows it on the display but it turns out there’s an Arudino library which solves some of these common problems with RPN builds like this.

One of the main reasons that RPN exists at all is that it is much easier for the processor in the calculator to understand the operations, even if it makes it a little bit harder for the human. This is because early calculators made much more overt use of a stack for performing operations in a similar way to Assembly language. Rather than learning Assembly, an RPN build like this can be a great introduction to this concept. If you want to get into the weeds of Assembly programming this is a great place to go to get started.

Lathe Outfitted With Electronic Gearbox

September 19, 2024 by Bryan Cockfield 45 Comments

Running a metal lathe is not for the faint of heart. Without proper knowledge and preparation, these machines can quickly cause injury or destroy expensive stock, tools, or parts. The other major problem even for those with knowledge and preparedness is that some of their more niche capabilities, like cutting threads with a lead screw, can be tedious and complicated thanks to the change gear system found on some lathes. While these are useful tools for getting things done, [Not An Engineer] decided that there was a better way and got to work building an electronic gearbox to automate the task of the traditional mechanical change gear setup in this video.

What makes change gears so tricky is that they usually come as a set of many gears of different ratios, forcing the lathe operator to figure out the exact combination of gears needed to couple the spindle of the lathe to the feed screw at the precise ratio needed for cutting a specific thread pattern. It is possible to do this task but can be quite a headache. [Not An Engineer] first turned to an Arduino Nano to receive input from a rotary encoder connected to the shaft of the lathe and then instruct a motor to turn the feed screw at a set ratio.

The first major problem was that the Arduino was not nearly fast enough to catch every signal from the encoder, leading to a considerable amount of drift in the output of the motor. That was solved by upgrading to a Teensy 4.1 with a 600 MHz clock speed. There was still one other major hurdle to cross; the problem of controlling the motor smoothly when an odd ratio is selected. [Not An Engineer] used this algorithm to inspire some code, and with that and some custom hardware to attach everything to the lathe he has a working set of electronic change gears that never need to be changed again. And, if you don’t have a lathe at all but are looking to get started with one, you can always build your own from easily-sourced parts.

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Build Yourself A Beautiful Interactive Light Toy

September 5, 2024 by Lewin Day 7 Comments

Sometimes, we build things with LEDs as indicator lamps or to illuminate something important. Sometimes, we build things with LEDs purely to glow and be beautiful. This interactive light toy from [Jens] falls into the latter category.

The build uses a 16×16 addressable LED matrix. [Jens] then ported some “Bouncy Bubbles” Processing code from Keith Peters to the Arduino Mega, and set it up to display on the matrix. An accelerometer was used to control the bouncing ball animations, while a second Arduino was then tapped to act as a musical synthesizer to add more vibes. The whole kit was then built into a 3D-printed housing with a nice hazy diffuser to give the LEDs a smoother, even look. [Jens] steps through how he got the diffuser just right, including a support structure that made all the difference to the aesthetic of the finished product. Getting diffusion right is key to making a nice LED project, and [Jens] got it very right here.

It’s a nice little art piece that looks kind of relaxing to play with in a dark room. We love a good glowable project here at Hackaday, so if you’ve built your own—don’t hesitate to let us know! Video after the break.

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A keyboard built into a commercial foot rest.

Floorboard Is A Keyboard For Your Feet

September 4, 2024 by Kristina Panos 8 Comments

Whether you have full use of your hands or not, a foot-operated keyboard is a great addition to any setup. Of course, it has to be a lot more robust than your average finger-operated keyboard, so building a keyboard into an existing footstool is a great idea.

When [Wingletang]’s regular plastic footrest finally gave up the ghost and split in twain, they ordered a stronger replacement with a little rear compartment meant to hold the foot switches used by those typing from dictation. Settling upon modifiers like Ctrl, Alt, and Shift, they went about designing a keyboard based on the ATmega32U4, which does HID communication natively.

For the switches, [Wingletang] used the stomp switches typically found in guitar pedals, along with toppers to make them more comfortable and increase the surface area. Rather than drilling through the top of the compartment to accommodate the switches, [Wingletang] decided to 3D print a new one so they could include circuit board mounting pillars and a bit of wire management. Honestly, it looks great with the black side rails.

If you want to build something a little different, try using one of those folding stools.

Supercon 2023: Teaching Robots How To Learn

September 3, 2024 by Lewin Day 2 Comments

Once upon a time, machine learning was an arcane field, the preserve of a precious few researchers holed up in grand academic institutions. Progress was slow, and hard won. Today, however, just about anyone with a computer can dive into these topics and develop their own machine learning systems.

Shawn Hymel has been doing just that, in his work in developer relations and as a broader electronics educator. His current interest is reinforcement learning on a tiny scale. He came down to the 2023 Hackaday Supercon to tell us all about his work.

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Two types of polymer clay hand warmers with a digital temperature controller.

Adjustable Electric Hand Warmers

August 30, 2024 by Kristina Panos 6 Comments

It may be the last gasp of summer here in the Northern Hemisphere, but it’s always cold somewhere, whether it’s outdoors or inside. If you suffer from cold, stiff hands, you know how difficult it can be to work comfortably on a computer all day. Somehow, all that typing and mousing does little to warm things up. What you need are hand warmers, obviously, and they might as well be smart and made to fit your hands.

Fifteen-year-old [Printerforge] created these bad boys in an effort to learn how to code LCDs and control heat like Magneto controls ferrous metals. Thanks to digital control, they can heat up to specific temperatures, and they happen to run for a long time.

Power-wise, these warmers use a 18650 cell and a TP4056 charging module. Everything is controlled by an Arduino Nano, which reads from both a thermistor and a potentiometer to control the output.

[Printerforge] really thought this project through, as you’ll see in the Instructable. There’s everything from a table of design requirements to quick but thorough explanations of nichrome wire and basic electronic theory.

And then there’s the material consideration. [Printerforge] decided that polymer clay offers the best balance of heat conductivity and durability. They ended up with two styles — flat, and joystick grip. The best part is, everything can fit in a generous pocket.

Clay is good for a lot of things, like making the perfect custom mouse.

RC Submarine Build Starts With Plenty Of Research

August 13, 2024 by Orlando Hoilett 19 Comments

[Ben]’s a 15-year-old who loves engineering and loves taking on new challenges. He’s made some cool stuff over the years, but the high water mark (no pun intended) has to be this impressively documented remote controlled submarine.

His new build starts off with more research than the actual building. [Ben] spent a ton of time investigating the design of the submarine from its shape, to the propeller system, to the best way to waterproof everything, keeping his sub in tip-top shape. He decides to go with the Russian-style Akula submarine, which is probably the generic look that most of us would think of when we hear the word submarine. He had some interesting thoughts on the propeller system (like the syringe ballast we’ve seen before), and which type of motor to use. In the end, he decided with four pumps that would act essentially as thrusters. ~~fill a chamber with water, allowing the submarine to submerge, or fill with air, making the submarine buoyant, allowing it to resurface.~~

However, what we found most interesting about his build is how he explains the rationale for all his design decisions and clearly documents his thought process on his project page. We really can’t do [Ben]’s project justice in a short post, so head over to his project page to see it for yourself.

While you’re at it, check out some of these other cool submarine builds that we’ve featured here on Hackaday