Mysterious Files PH

Transistors in some circuit configurations work together and, frequently, need to be matched. This is so common that you can sometimes find ICs that are just a pair of transistors made with the same piece of silicon, so they should be matched very closely by default. But with discrete transistors, two devices of the same type are not always identical. [Learn Electronics Repair] covers the topic and explains how to match devices in the video below.

Depending on the circuit, the matching parameters may be different, but generally, the idea is that you want similar gains or matching saturation characteristics. The reason is that when you have multiple transistors working together, you don’t want one to do more work than the other device. This is inefficient and could drive the “better” component to fail.

The same idea applies in bridge circuits, where you might match resistors or capacitors to make sure that, for example, two 10% resistors are very close to the same value. A 10K resistor could be between 9K and 11K, and you might not care as long as they are both, say, 9.2K or both 10.8K.

This is different, by the way, from impedance matching, where you achieve maximum power transfer by matching a source to a load.

Once upon a time, someone set up a livestream wherein the messages from Twitch chat could control a game of Pokemon. Since then, we’ve seen Twitch control all sorts of things. If you’d like to have them play with some LEDs in your house, you might like this project from [pfeiffer3000].

The concept is simple enough. The heart of the build is an ESP32 microcontroller, which is easy to integrate with web services thanks to its onboard WiFi capability. It’s hooked upt o a string of WS2812B addressable RGB LEDs. The LEDs themselves are installed within table tennis balls to act as nice, spherical diffusers, and installed in a square frame made of PVC pipes. As for code, the rig uses the WLED library to drive the LED strings, and code from TwitchIO to interface with Twitch chat itself. It’s as simple as rigging up a bit of Python. With everything assembled, [pfeiffer3000] had an attractive LED grid that could be controlled directly by anyone watching their Twitch stream.

We’ve explored how to control things via Twitch before, too. It’s a fun way to add some interactivity to your livestream that really gets viewers involved. If you’ve been building your own audience-controlled projects, we’d love to hear about them on the tipsline!

Some people love CRTs to a degree that the uninitiated may find obsessive. We all have our thing, and for [Found Tech], it’s absolutely pointing particle accelerators at his face to play video games. He likes modern games, with modern resolutions– none of this 1080p nonsense. Today’s gamers demand 4K! Can a CRT keep up? The answer is a resounding “No, but actually, yes!”

[Found Tech] has an IBM P275 monitor, which is one of the last generation of CRTs.  Officially, the resolution maxes out at 1920 dots by 1440 lines. While one might (inaccurately) call that UHD output “2K”, you certainly cannot claim it is 4K. So, what’s the secret? Interlacing. Yes, interlacing, like old analog TV signals.

Apparently, in spite of what the manual says, getting the screen to absorb the 2880×2160 interlaced signal wasn’t the hard part, but generating it was. NVIDIA and AMD graphics cards are absolutely unable to create an interlaced signal, but Intel integrated GPUs are– if you get the right combo of chip and old driver. Sadly, the video doesn’t list exactly what he used. Of course an iGPU isn’t going to give you a very good gaming experience at this high resolution, so [Found Tech] has his games do their rendering on the discrete card before piping that over to the iGPU for display on the CRT.

Technically, you still can’t call the 2880×2160 picture “4K”, as that trademark refers to 2160p at 16:9, and this is both interlaced and 4:3. Still, close enough. In spite of the artifacting that turned us all against interlaced signals back in the day, this apparently has [Found Tech]’s eyes fooled– he says it’s as good as 2160p on his OLED, plus the extra magic that comes with glowing phosphors.

It certainly looks great in a recording, but the monitor in the recording isn’t displayed at a high enough resolution to say for sure if it’s 4K. Still, if you’re into CRT gaming, maybe give this high-res interlacing a try. If you still don’t get what’s so great about CRTs, check here, and remember it could be worse– at least we’re not going on about Plasma TVs.

There are lots of smart home systems that will let you blast your older dumb appliances with infrared to control them. However, many are tied to ugly cloud systems that can frustrate you on a regular basis. [Steelcuts] whipped up a cloudless solution to this problem instead.

IR2MQTT does pretty much exactly what it says in the name. It allows integrating things like air conditioners and televisions into a Home Assistant setup with the use of an IR blaster and a neat, tidy web app. You use it with an ESP32 or ESP8266 running a firmware based on ESPHome to actually do the IR blasting. In turn, IR2MQTT is a back-end plus a web interface that lets you setup all your IR devices without having to manually capture IR codes and create YAML files to do everything. It’s also integrated with large databases of IR codes for common appliances so in many cases, you can just look up your gear and get it working the easy way.

Sometimes all you need to get the job done is an IR LED and the will to use it. If you’re cooking up your own infrared hacks, don’t hesitate to let us know on the tipsline.

You can get all kinds of fancy lenses for modern cameras, with all sorts of mechanical and electronic wizardly to make them shoot better images. But what if you paired a vintage lens with a modern camera? It would take some work, as [Mathieu] found out, but you’d also get some interesting results.

The optic in question is a 100-year old lens—a Foth 50 mm f2.5 to be precise, originally used with a folding film camera. It was sourced from a market for just 3 euros. Notably, the lens was not designed for modern cameras, and so lacks an aperture and focusing mechanism. [Mathieu] thus had to fabricate something to fit the lens to a Sony FX3. A first attempt used an aperture adapter from Amazon and an elcoid adapter, but there were vignetting problems due to the lens placement in this case. Ultimately, [Mathieu] went with a special macro adapter that allowed him to control focus and tuck in an ND filter behind the lens, which made up for the lack of an aperture.

The vintage glass isn’t the sharpest lens out there, but that’s kind of what’s fantastic about it. The center of the frame is certainly focused, but it fades out softly towards the edges of the image, giving a cinematic, dreamlike effect. The bokeh in the background are particularly charming, too. As far as 3 euro lenses go, this one was a hit.

You can slap just about any lens on anything if you get creative with how you do it. Video after the break.

[Thanks to Stephen Walters for the tip!]

Continuing his quest to put DOOM on literally everything that has a capable enough processor and a screen, [Aaron Christophel]’s most recent target is a Slate 7 Pro travel router. With a generous 2.8″ touch screen and a lot of onboard processing power to handle all the advertised networking and routing features via its WAN and (W)LAN interfaces, it should be able to run the game really quite well. As usual the main question is how to get the game to run on it first.

The port of choice is fbdoom, with instructions on how to run it on this router provided on the GitHub project page. The reason for the touch screen is so that you can see the status of interfaces and interact with it without having to open the web interface. Boringly, this router has an SSH daemon ready to connect to, giving you full root access to the Linux-based firmware.

It’s just your typical AArch64 ARM-based system, with the gl_screen process running for the touch screen display. From there it was easy enough to deduce the settings to jot into fbdoom so that it too could use the same screen and touch inputs. After copying the compiled binary with SCP over to the router, it can then be started like any application. With touch inputs somewhat awkwardly mapped to certain areas of the touch screen, it’d be nice to see the USB 2.0 port used for USB HID inputs, but it does show how easy things can be when it runs something like Linux and you got full root access.

Incidentally this also heavily blurs the lines between something like a Valve Steamdeck and a router, with the latter just missing some gamepad controls on the side to do some on-the-go gaming when you’re not using it for routing network traffic.

Phones can be distracting objects if you’re not an enlightened master of the mental arts. Even just reading an email or glancing at your calendar can get you caught up checking other apps and notifications and waste your time. [Paul Lagier] built a device to eliminate this problem by showing him critical information right on his desk.

The device is based around an off-the-shelf Waveshare ESP32 board which packs in a small 8×8 RGB LED matrix on one side. It’s a neat way to get an LED project up and running quickly, but [Paul] noted that it didn’t look that great out of the box. He had to experiment with some different solutions for diffusing the light, eventually wrapping the board in a 3D printed housing with a black grid to separate the light output from each LED to make a clear pixelated display.

The ESP32’s wireless connectivity comes in handy, because it’s able to query web services for [Paul’s] calendar and other useful data. The user interface is minimal—you merely flip the housing into a different orientation to display different information, relying on the onboard QMI8658 6-axis sensor. The main display shows [Paul’s] calendar in 15 minute blocks so he can keep track of meetings without having to open his phone. Shaking the device in this mode will display the events as scrolling text. There’s also an ambient mode that looks pretty, and a pairing mode for setting up the wireless connectivity.

The great thing about modern electronic hardware is that it’s very easy to produce productivity aids like this to suit your own lifestyle.