Over on YouTube [Lockdown Electronics] reviews an old bit of kit known as the Silicon Controlled Rectifier (SCR). Invented in the 1950s the SCR is a type of thyristor and they were popular back in the 1970s. They are often replaced these days by the TRIAC and the MOSFET but you might still find some old schematics that call for them and you can still buy them.
The SCR is a three terminal electronic switch which latches on. You apply a signal at the gate which allows the other two pins, the anode and cathode, to conduct; and they continue to do so until power is removed. The silicon inside the device is comprised of three semiconductor junctions, as: PNPN. The P on the left is the anode, the N on the right is the cathode, and the P in the right middle is the gate.
Fitting wheels to shafts and motors to a frame can be a bit tricky when none were made with the other in mind.
The purchased Dalek is made of wood and, with the help of two bolts, is of sufficient size to trap a human inside. There’s a bench of sorts upon which the captive can sit, and with some effort, shuffle the surrounding frame awkwardly about. The scale of the Dalek is impressive, but it was clear the effect of human-powered locomotion was lacking. The solution was to install wheelchair motors, tires, and an ESP32-based remote control.
Quite a lot of work went into mounting the motors and wheels, and the challenges will be familiar to anyone who has done hobby robotics. One can choose ideal motors and wheels, but making them fit one another can be an entirely different story. Shafts and hubs are of different sizes, motor mounting doesn’t quite match the platform, and it’s all a bit like fitting a square peg into a round hole. But with access to the right tools, it’s nothing a little metalwork and welding can’t solve.
For the control system, the ESP32 (with a beautiful CNC-routed custom PCB) sets itself up as a wireless access point that serves a web-based control panel for piloting, and controls two H-bridges to drive the motors. What’s more, it also provides a sound board from which a second operator can trigger appropriate phrases and sounds from the Dalek.
Some folks prefer their remote-controlled Daleks plush and cute instead of large and looming, but we like the smooth movement and imposing stature of this one. Watch it all in action in the video, embedded below.
Pagers were once a great way to get a message to someone out in public; they just had to be cool enough to have one. These days, they’re mostly the preserve of doctors and a few other niche operators. [Kyle Tryon] is bringing the beeper back, though, with a custom ESP32-based build.
The ESP32 is a great microcontroller for this kind of project, because it’s got WiFi and Bluetooth connectivity built right in. This let [Kyle] write some straightforward code so that it could receive alerts via MQTT. In particular, it’s set up to go off whenever there’s an app or service notification fired off by the Sentry platform. For [Kyle]’s line of work, it’s effectively an on-call beeper that calls them in when a system needs immediate attention. When it goes off, it plays the ringtone of your choice—with [Kyle] making it capable of playing tunes in Nokia’s old-school RTTTL music format.
The code was simple enough, and the assembly wasn’t much harder. By starting with an Adafruit ESP32 Reverse TFT Feather, the screen and buttons were all ready to go right out of the box. [Kyle] merely had to print up a rad translucent case on a resin printer to make it look like a sweet fashionable beeper from the 90s.
Want to visualize radioactive particles? You don’t need a boatload of lab equipment. Just a cloud chamber. And [Curious Scientist] is showing off an improved miniature cloud chamber that is easy to replicate using a 3D printer and common components.
The build uses a Peltier module, a CPU cooler, an aluminum plate, thermal paste, and headlight film. The high voltage comes from a sacrificed mosquito swatter. The power input for the whole system is any 12V supply.
The cloud chamber was high tech back in 1911 when physicist Charles T. R. Wilson made ionizing radiation visible by creating trails of tiny liquid droplets in a supersaturated vapor of alcohol or water. Charged particles pass through, leaving visible condensation trails.
We’ve often said that some technological advancements seemed like alien technology for their time. Sometimes we look back and think something would be easy until we realize they didn’t have the tools we have today. One of the biggest examples of this is how, in the 1950s, engineers created a color image that still plays on a black-and-white set, with the color sets also able to receive the old signals. [Electromagnetic Videos] tells the tale. The video below simulates various video artifacts, so you not only learn about the details of NTSC video, but also see some of the discussed effects in real time.
Creating a black-and-white signal was already a big deal, with the video and sync presented in an analog AM signal with the sound superimposed with FM. People had demonstrated color earlier, but it wasn’t practical for several reasons. Sending, for example, separate red, blue, and green signals would require wider channels and more complex receivers, and would be incompatible with older sets.
An uncut lacquer master is an aluminum base coated with a flawless layer of lacquer. It smells like fresh, drying paint.
Cutting a lacquer master is the intricate process by which lacquer disks, used as the masters for vinyl records, are created. These glossy black masters — still made by a company in Japan — are precision aluminum discs coated with a special lacquer to create a surface that resembles not-quite-cured nail polish and, reportedly, smells like fresh paint.
The cutting process itself remains largely unchanged over the decades, although the whole supporting setup is a bit more modernized than it would have been some seventy years ago. In the video (embedded below), we get a whole tour of the setup and watch a Neumann AM32B Master Stereo Disk Recording Lathe from 1958 cut the single unbroken groove that makes up the side of a record.
The actual cutting tool is a stylus whose movement combines the left and right channels and is heated to achieve the smoothest cuts possible. The result is something that impresses the heck out of [Technostalgism] with its cleanliness, clarity, and quality. Less obvious is the work that goes into arranging the whole thing. Every detail, every band between tracks, is the result of careful planning.
We all know that you can play DOOM on nearly anything, but what about the lesser known work being done to let other species get in on the action? For ages now, our rodent friends haven’t been able to play the 1993 masterpiece, but [Viktor Tóth] and colleagues have been working hard to fix this unfortunate oversight.
If you’ve got the feeling this isn’t the first time you’ve read about rats attempting to slay demons, it’s probably because [Victor] has been working on this mission for years now — with a previous attempt succeeding in allowing rats to navigate the DOOM landscape. Getting the rodents to actually play through the game properly has proved slightly more difficult, however.
Improving on the previous attempt, V2 has the capability to allow rats to traverse through levels, be immersed in the virtual world with a panoramic screen, and take out enemies. Rewards are given to successful behaviors in the form of sugar water through a solenoid powered dispenser.
While this current system looks promising, the rats haven’t gotten too far though the game due to time constraints. But they’ve managed to travel through the levels and shoot, which is still pretty impressive for rodents.
DOOM has been an indicator of just how far we can take technology for decades. While this particular project has taken the meme into a slightly different direction, there are always surprises. You can even play DOOM in KiCad when you’re tired of using it to design PCBs.
