Humble Television Tubes Make An FM Regenerative Radio

November 4, 2024 by Jenny List No comments

The regenerative radio is long-ago superseded in commercial receivers, but it remains a common project for electronics or radio enthusiasts seeking to make a simple receiver. It’s most often seen for AM band receivers or perhaps shortwave ham band ones, but it’s a circuit which also works at much higher frequencies. [Perian Marcel] has done just this, with a regenerative receiver for the FM broadcast band.

The principle of a regenerative receiver is that it takes a tuned radio frequency receiver with a wide bandwidth and poor performance, and applies feedback to the point at which the circuit is almost but not quite oscillating. This has the effect of hugely increasing the “Q”, or quality factor of the receiver, giving it much more sensitivity and a narrow bandwidth. They’re tricky to tune but they can give reasonable performance, and they will happily slope-demodulate an FM transmission.

This one uses two tubes from consumer grade TV receivers, the “P” at the start of the part number being the giveaway for a 300mA series heater chain. The RF triode-pentode isn’t a radio part at all, instead it’s a mundane TV field oscillator part pushed into service at higher frequencies, while the other triode-pentode serves as an audio amplifier. The original circuit from which this one is adapted is available online, All in all it’s a neat project, and a reminder that exotic parts aren’t always necessary at higher frequencies. The video is below the break.

Continue reading “Humble Television Tubes Make An FM Regenerative Radio” →

M.2 Makes An Unusual Microcontroller Form Factor

November 3, 2024 by Jenny List 35 Comments

When we think of an m.2 slot in our laptop or similar, it’s usually in the context of its PCI connectivity for high-speed applications such as solid state disks. It’s a connector that offers much more than that interface though, making it suitable for some unexpected add-ons. As an example [MagicWolfi] has produced an m.2 card which contains the equivalent of a Raspberry Pi Pico.

The board itself has the familiar m.2 edge connector at the bottom, and the RP2040 GPIO lines as postage-stamp indentations round the edges. On the m.2 front is uses the USB interface as well as a UART and the I²C lines, as well as some of the interfaces we’re less familiar with such as ALERT, WAKE, DISABLE1/2, LED 1/2, and VENDOR_DEFINED.

On one level this provides a handy internal microcontroller card with which you can do all the things you’d expect from a Pi Pico, but on another it provides the fascinating possibility of the Pico performing a watchdog or other function for the host device. We would be genuinely interested to hear more about the use of the m.2 slot in this way.

If you’d like to know more about m.2, we’ve taken a look at it in more depth.

Don’t Forget Your Curve Tracer

November 2, 2024 by Jenny List 4 Comments

As cheap microcontrollers have given us an impressive range of test equipment trinkets to play with, it’s easy to forget some of the old standabys. A curve tracer for example, the relatively simple circuit allowing the plotting of electronic component response curves on an oscilloscope. Lest we forget this useful device, here’s [Gary LaRocco] with a video describing one that’s so easy to build, anyone could do it.

It’s a simple enough premise, a low AC voltage comes from a mains transformer and is dropped down to the device under test through a resistor. The X and Y inputs of the ‘scope are configured to show the current and the voltage respectively, and the result is a perfect plot of the device’s IV curve. The best part is that it’s designed for in-circuit measurement, allowing it to be used for fault-finding. There’s a demonstration at the end with a variety of different parts, lest we needed any reminder as to how useful these devices can be.

The cost of one of these circuits is minimal, given that the transformer is likely to come from an old piece of consumer electronics. It’s not the first simple curve tracer we’ve seen, but we hope it will give you ideas. The video is below the break.

Continue reading “Don’t Forget Your Curve Tracer” →

Capturing Light In A Vacuum: The Magic Of Tube Video Cameras

November 1, 2024 by Jenny List 30 Comments

Cameras are a funny rabbit hole to fall down as a hacker, because we have well over a century of items to pick and choose from, a lot of which can be had for relative pennies. In my case I have more of them than I’d care to mention, mostly film cameras and 8mm movie cameras, but there are one or two that are entirely different. My first interest in electronics came through PAL televisions, so it’s hardly surprising that along the way I’ve also acquired more than one chunky old tube-based video camera. These devices are now long ago supplanted by their solid state replacements, but they retain a fascination for me as the mirror of the CRT-based TV sets I know so well. It’s time for a fascinating descent into the world of analogue video.

Electrons chasing light, chasing electrons

The zig-zag line pattern of a TV scan. — A raster scan pattern. Ian Harvey, Public domain.

The basic mode of operation behind all but some of the very earliest electronic camera tubes is that an electron gun paints its raster of electrons onto a light-sensitive target, and the current flowing through the electron beam varies in proportion to the light at each particular point on the target. This can be used to create a voltage, which when combined with the various sync pulses makes a video signal that would be understood by a monitor. The various different types of tubes have names such as Iconoscope, Emitron, or Vidicon, and while the main differences between those various types of tube lie in the combination of materials and design of their targets. Successive generations of tube made improvements to sensitivity and noise performance, first combining photoemissive layers with electron multiplying layers to amplify the video signal in much the same way as a photomultiplier tube does, and then using photoconductive targets to vary the conductivity of the target depending on the light at a particular point. Continue reading “Capturing Light In A Vacuum: The Magic Of Tube Video Cameras” →

3D Printing With A Hot Glue Gun

October 31, 2024 by Jenny List 14 Comments

Face it, we’ve all at some time or other looked at our hot glue guns, and thought “I wonder if I could use that for 3D printing!”. [Proper Printing] didn’t just think it, he’s made a working hot glue 3D printer. As you’d expect, it’s the extruder which forms the hack here.

A Dremel hot glue gun supplies the hot end, whose mains heater cartridge is replaced with a low voltage one with he help of a piece of brass tube. He already has his own design for an extruder for larger diameters, so he mates this with the hot end. Finally the nozzle is tapped with a thread to fit an airbrush nozzle for printing, and he’s ready tp print. With a much lower temperature and an unheated bed it extrudes, but it takes multiple attempts and several redesigns of the mechanical parts of the extruder before he finally ended up with the plastic shell of the glue gun as part of the assembly.

The last touch is a glue stick magazine that drops new sticks into a funnel on top of the extruder, and it’s printing a Benchy. At this point you might be asking why go to all this effort, but when you consider that there are other interesting materials which are only available in stick form it’s clear that this goes beyond the glue. If you’re up for more hot glue gun oddities meanwhile, in the past we’ve shown you the opposite process to this one.

Continue reading “3D Printing With A Hot Glue Gun” →

An Electric Vehicle Conversion With A Difference

October 30, 2024 by Jenny List 25 Comments

For a first try at an electric vehicle conversion we’re guessing that most would pick a small city car as a base vehicle, or perhaps a Kei van. Not [LiamTronix], who instead chose to do it with an old Ferguson tractor. It might not be the most promising of EV platforms, but as you can see in the video below, it results in a surprisingly practical agricultural vehicle.

A 1950s or 1960s tractor like the Ferguson usually has its engine as a structural member with the bellhousing taking the full strength of the machine and the front axle attached to the front of the block. Thus after he’s extracted the machine from its barn we see him parting engine and gearbox with plenty of support, as it’s a surprisingly hazardous process. These conversions rely upon making a precise plate to mount the motor perfectly in line with the input shaft. We see this process, plus that of making the splined coupler using the center of the old clutch plate. It’s been a while since we last did a clutch alignment, and seeing him using a 3D printed alignment tool we wish we’d had our printer back then.

The motor is surprisingly a DC unit, which he first tests with a 12 V car battery. We see the building of a hefty steel frame to take the place of the engine block in the structure, and then a battery pack that’s beautifully built. The final tractor at the end of the video still has a few additions before it’s finished, but it’s a usable machine we wouldn’t be ashamed to have for small round-the-farm tasks.

Surprisingly there haven’t been as many electric tractors on these pages as you’d expect, though we’ve seen some commercial ones.

Continue reading “An Electric Vehicle Conversion With A Difference” →

An International Hackerspace Map

October 29, 2024 by Jenny List 17 Comments

If you’re looking for a hackerspace while on your travels, there is more than one website which shows them on a map, and even tells you whether or not they are open. This last feature is powered by SpaceAPI, a standard way for hackerspaces to publish information about themselves, including whether or not they are closed.

Given such a trove of data then it’s hardly surprising that [S3lph] would use it to create a gigantic map of central Europe with lights in the appropriate places (German language, Google Translate link) to show the spaces and their status.

The lights are a set of addressable LEDs and the brain is an ESP32, making this an accessible project for most hackers with the time to assemble it. Unsurprisingly then it’s not the first such map we’ve seen, though it’s considerably more ambitious than the last one. Meanwhile if your hackerspace doesn’t have SpaceAPI yet or you’re simply curious about the whole thing, we took a look at it back in 2021.

Thanks [Dave] for the tip.