In retrocomputing circles, it’s often the case that the weirder and rarer the machine, the more likely it is to attract attention. And machines don’t get much weirder than the DEC Rainbow 100-B, sporting as it does both Z80 and 8088 microprocessors and usable as either a VT100 terminal or as a PC with either CP/M or MS-DOS. But hey — at least it got the plain beige box look right.

Weird or not, all computers have at least a few things in common, a fact which helped [Dr. Joshua Reichard] home in on the problem with a Rainbow that was dead on arrival. After a full recapping — a prudent move given the four decades since the machine was manufactured — the machine failed to show any signs of life. The usual low-hanging diagnostic fruit didn’t provide much help, as both the Z80 and 8088 CPUs seemed to be fine. It was then that [Joshua] decided to look at the heartbeat of the machine — the 24-ish MHz clock shared between the two processors — and found that it was flatlined.

Unwilling to wait for a replacement, [Joshua] cobbled together a temporary clock from an Arduino Uno and an Si5351 clock generator. He connected the output of the card to the main board, whipped up a little code to generate the right frequency, and the nearly departed machine sprang back to life. [Dr. Reichard] characterizes this as a “defibrillation” of the Rainbow, and while one hates to argue with a doctor — OK, that’s a lie; we push back on doctors all the time — we’d say the closer medical analogy is that of fitting a temporary pacemaker while waiting for a suitable donor for a transplant.

This is the second recent appearance of the Rainbow on these pages — [David] over at Usagi Electric has been working on the graphics on his Rainbow lately.

One of the things missing from the “classic” Arduino experience is debugging. That’s a shame, too, because the chips used have that capability. However, the latest IDE has the ability to work with external debuggers and if you want to get started with a classic ATMega Arduino, [deqing] shows you how to get started with a cheap CH552 8-bit USB microcontroller board as the debugging dongle.

The CH552 board in question is a good choice, primarily because it is dirt cheap. There are design files on GitHub (and the firmware), but you could probably pull the same trick with any of the available CH552 breakout boards.

There was a time when having a god-eye view of your embedded system required an expensive in-circuit emulation system. These were expensive, difficult to deploy, and rare. Then, CPUs started adding debugging hardware right on the chip. A few spare pins on the CPU and some sort of adapter would give you most of what you wanted from an emulation system. Although these adapters are often proprietary, sometimes they aren’t, or they have been reverse-engineered. If you know the protocol, it is easy enough to get a processor to speak it for you. That’s why you often see, for example, Raspberry Pi Picos debugging other Picos. There’s nothing you can’t do a million other ways here, but it is an excellent step-by-step tutorial for getting started without breaking the bank.

The old adage that you’ll make a fortune by developing a better mouse trap is not super realistic, as the engineers behind Sony’s Betamax video tape standard could tell you. However, you can still learn a lot building your own, as this project from [ROBO HUB] demonstrates.

The trap is intended to catch mice in a humane fashion, without injury to the animal. To that end, it uses an Arduino Nano armed with an ultrasonic distance sensor  to detect when mice have entered a plastic container. The container’s hinged door is is held open with a servo. When a mouse is detected, the servo trips the door to snap shut under the power of an elastic band.

The key to making this design work well is ensuring that there are no gaps in the closed container that the mouse can use to escape. They’re wily creatures able to squeeze through positively tiny spaces, so it’s important to get this right. Besides that, you want to check the trap regularly, lest any caught mice simply claw and chew their way out.

We’ve seen a few mousetraps around these parts before, too. Video after the break.

While not every camera mount needs to have six degrees of freedom, one or two can be extremely helpful in the photographic world. In order to make time-lapse shots with some motion or shots that incorporate some parallax, a moving camera mount or dolly is needed, and this small one builds upon a pre-existing, although non-motorized, camera slider.

The slider is an inexpensive model from everyone’s favorite online warehouse, with rails that are at least coated in carbon, if not made out of it entirely, to ensure smooth camera motion. To add the motorization to automatically move the camera, a stepper motor with a belt drive is used which is controlled by an Arduino. A few limit switches are added, letting the dolly perform different movement patterns automatically, and a pair of potentiometers for fine and coarse speed control are included as well, letting the camera take both time-lapse and video while using this mount at various controllable speeds.

With everything tucked into a relatively small box at one end of the dolly, the build is both accessible and functional. The code for the microcontroller is also available on the project’s GitHub page for anyone looking to replicate or build upon the project. And, for those looking to add more degrees of freedom to their camera setups, take a look at this DIY pan and tilt mount.

Most of us are content to get our semiconductors from the usual sources, happily abstracting away the complexity locked within those little epoxy blobs. But eventually, you might get the itch to roll your own semiconductors, in which case you’ll need to start gearing up. And one of the first tools you’ll need is likely to be something like this DIY tube furnace.

For the uninitiated, [ProjectsInFlight] helpfully explains in the video below just what a tube furnace is and why you’d need one to start working with semiconductors. Perhaps unsurprisingly, a tube furnace is just a tube that gets really, really hot — like 1,200° C. In addition to the extreme heat, commercial furnaces are often set up to seal off the ends of the tube to create specific conditions within, such as an inert gas atmosphere or even a vacuum. The combination of heat and atmospheric control allows the budding fabricator to transform silicon wafers using chemical and physical processes.

[ProjectsInFlight]’s tube furnace started with a length of heat-resistant quartz glass tubing and a small tub of sodium silicate refractory cement, from the plumbing section of any home store. The tube was given a thin coat of cement and dried in a low oven before wrapping it with nichrome wire. The wrapped tube got another, thicker layer of silicate cement and an insulating wrap of alumina ceramic wool before applying power to cure everything at 1,000° C. The cured tube then went into a custom-built sheet steel enclosure with plenty of extra insulation, along with an Arduino and a solid-state relay to control the furnace. The video below concludes with testing the furnace by growing a silicon dioxide coating on a scrap of silicon wafer. This was helped along by the injection of a few whisps of water vapor while ramping the furnace temperature up, and the results are easily visible.

[ProjectsInFlight] still needs to add seals to the tube to control the atmosphere in there, an upgrade we’ll be on the lookout for. It’s already a great start, although it might take a while to catch up to our friend [Sam Zeloof].

Low-power radios, often referred to in the amateur radio community as QRP radios, have experienced a resurgence in popularity lately. Blame it on certain parts of the hobby become more popular, like Parks on the Air (POTA) or Summits on the Air (SOTA). These are events where a radio operator operates off-grid at remote parks or mountaintops. These QRP rigs are a practical and portable way to make contacts. You would think that a five- or ten-watt rig running on batteries would be simple. Surprisingly, they can be enormously complex and expensive. That’s why [Stephen] built the RFBitBanger, a QRP radio designed to not only be usable off-grid but to be built and maintained off-grid as well.

The radio accomplishes this goal by being built out of as many standard off-the-shelf components as possible. It eschews modern surface-mount components in favor of the much more accessible through-hole parts, including the ATMEGA328P at the center of the build. A PCB design is also available, but it can be built on perf board nearly as easily. The radio supports any mode a QRP operator might use, including CW, SSB, RTTY, and a new mode designed explicitly for this radio called SCAMP which is a low bandwidth, low SNR digital mode built into the Arduino-based firmware. It’s a single-band radio, but any band between 20 and 80 meters can be selected with pluggable filters.

As far as bomb-proof radios go, we can’t imagine a better way to live out an apocalypse than with a radio like this. As long as there’s a well-stocked parts drawer around, this radio could theoretically reach around the world without worrying about warranty claims, expensive parts, or even a company going out of business or not stocking parts for old radios anymore. There’s also more information about this build at the Open Research Institute for those interested. And, if you’re wondering how useful any radio could be using only five watts of transmitter power, take a look at this in-depth look at QRP radio operation.

Do you know how you see those cheap telescopes at the department store? The box has beautiful pictures that probably came from the Hubble. What you will see is somewhat different. You have to carefully look at [upir’s] Arduino thermal camera project because it intersperses pictures of what you expect an 8×8 sensor will produce with images produced by a much better camera.

The actual project — watch the video below — is undoubtedly neat. An inexpensive 8×8 IR sensor and an 8X8 LED panel join to form a crude but usable thermal camera.

He leverages several ready-made libraries and walks through how and why he chose them and how he had to modify them. We enjoyed the demo of plotting HSV values to the LED array instead of the usual RGB values.

Given canned code to read the sensor and drive the LEDs, the rest is easy. Of course, like the dime-store telescope, you aren’t going to get amazing results. On the other hand, you probably have everything you need except the $20 sensor sitting around doing nothing anyway.

At around the ten-minute mark, he shows the same sensor in a commercial module that interpolates a higher resolution to an LCD. Still crude, so he also gives a quick review of a commercial camera that plugs into your phone. (You can ignore the video from here on if the stealth advertising bugs you.) We’ve actually looked at that camera before. We’ve also looked at some of the competition. While any of those will beat the 8×8 Arduino camera, they’ll cost more and won’t give you the satisfaction of building it, either.

For the last ten to fifteen years, optical drives have been fading out of existence. There’s little reason to have them around anymore unless you are serious about archiving data or unconvinced that streaming platforms will always be around. While there are some niche uses for them still, we’re seeing more and more get repurposed for parts and other projects like this laser engraver which uses not only the laser from a DVD drive, but plenty of other parts as well.

The build starts with a couple optical drives, both of which are dismantled. One of the shells is saved to use as a base for the engraver, and two support structures are made out of particle board and acrylic to hold the laser and the Y axis mechanism. Both axes are made from the carriages of the disassembled hard drives, with the X axis set into the base to move the work piece. One of the lasers from the scavenged DVD drives is fitted to the Y axis with a new heat sink, and with an Arduino set up to interpret gcode the device is on its way to engraving any material that will fit into its diminutive frame.

While the build repurposes almost all of the parts from the optical drives, it does stop short of using the drive motors in favor of A4988 stepper motors. It’s also not quite powerful enough to engrave wood, but other materials like leather are right in this machine’s sweet spot. If you have plenty of drives on hand with nothing else for them to do, there’s plenty more they can be used for. This scanning laser microscope is among the more interesting builds we’ve seen.

The most collectible items in the realm of vintage computers often weren’t the most popular of their era. Quite the opposite, in fact. Generally the more desireable systems were market failures when they first launched, and are now sought out because of a newly-appreciated quirk or simply because the fact that they weren’t widely accepted means there’s fewer of them. One of the retro computers falling into this category is the Apple III, which had fundamental hardware issues upon launch leading to a large recall and its overall commercial failure. [Ted] is trying to bring one of these devices back to life, though, by slowing its clock speed down to a crawl.

The CPU in these machines was a Synertek 6502 running at 1.8 MHz. With a machine that wouldn’t boot, though, [Ted] replaced it with his own MCL65+, a purpose-built accelerator card based on the 600 MHz Teensy 4.1 microcontroller in order to debug the motherboard. The first problem was found in a ROM chip which prevented the computer loading anything from memory, but his solution wouldn’t work at the system’s higher clock speeds. To solve that problem [Ted] disabled the higher clock speed in hardware, restricting the system to 1 MHz and allowing it to finally boot.

So far there haven’t been any issues running the computer at the slower speed, and it also helps keep the computer cooler and hopefully running longer as well, since the system won’t get as hot or unstable. This isn’t [Ted]’s first retrocomputing rodeo, either. His MCL chips have been featured in plenty of other computers like this Apple II which can run at a much faster rate than the original hardware thanks to the help of the modern microcontroller.

When it comes to controllers for racing games, there is perhaps no better option than a force feedback steering wheel. With a built-in motor to push against the wheel at exactly the right times, they can realistically mimic the behavior of a steering wheel from a real car. The only major downside is cost, with controllers often reaching many hundreds of dollars. [Jason] thought it shouldn’t be that hard to build one from a few spare parts though and went about building this prototype force feedback steering wheel for himself.

Sourcing the motor for the steering wheel wasn’t as straightforward as he thought originally. The first place he looked was an old printer, but the DC motor he scavenged from it didn’t have enough torque to make the controller behave realistically, so he turned to a high-torque motor from a battery-powered impact driver. This also has the benefit of coming along with a planetary gearbox as well, keeping the size down, as well as including its own high-current circuitry. The printer turned out to not be a total loss either, as the encoder from the printer was used to send position data about the steering wheel back to the racing game. Controlling the device is an Arduino, which performs double duty sending controller information from the steering wheel as well as receiving force feedback instructions from the game to drive the motor in the steering wheel.

After 3D printing a case for it and strapping it to a work bench, the initial tests proved to be promising. [Jason] can feel the motor from the power drill pushing against the steering wheel at the appropriate time. However there are some issues to work out with the prototype as the coupling mechanism between the motor and steering wheel isn’t strong enough to resist skipping and is likely to eventually break. We look forward to future videos when these issues are ironed out, but in the meantime we’d recommend taking a look at this force feedback mouse for other ways of making video game experiences more immersive.