Demonstrating The Photoelectric Effect Using Neon Lamps

August 28, 2024 by 30 Comments

Neon lamps are fun to play with. These old-school indicators were once heavily utilized in many types of equipment for indication purposes but now seem largely relegated to mains voltage indication duties. Here’s a fun video by [Ashish Derhgawen], discussing the photoelectric effect of neon lamps with some simple demonstrations.

Orange light makes it light!

[Ashish] demonstrates the well-known photoelectric effect by triggering a sub-biased neon lamp with visible light from an LED. Neon bulbs work on the principle of voltage-induced ionization, creating a visible glowing plasma. If the applied voltage is high enough, around 60 to 80 V, electrons get knocked off the neutral neon atoms. The now free electrons, roaming around highly energized, will eventually come across a neon ion (missing an electron) and recombine to make it neutral again.

The results are a lower total energy state, and the difference in energy is resolved by the emission of a photon of light, which, in the case of neon, is a dull reddish-orange. Nothing unusual there. However, nothing will happen if the applied voltage bias is just below this device-specific threshold. There’s not enough energy to strip electrons.

Apply an external light source, and this threshold can be exceeded. The photons from the LED are just energetic enough to strip a small number of electrons from the surface of the electrodes, and this causes a cascade, or avalanche effect, lighting up the plasma and turning on the neon lamp. Take away the external light source, and it dies down and goes dark.

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Proper Mag Lev Controller Makes Snail Lamp Much Cooler

August 28, 2024 by 5 Comments

Magnetic levitation has not quite revolutionized the world of transit the way some of us might have hoped. It has, however, proven useful to [mrdiytechmagic], who has put the technology to grand use in making his levitating snail lamp.

The build is actually relatively complicated compared to some levitating toys you might have seen before. It uses a number of coils to produce a magnetic field to levitate the 3D printed plastic snail which contains the lighting element itself.

The actively controlled levitation base uses a magnetic sensor to detect the changing field as the snail moves above it. It then varies the current going to the various coils to keep the snail balanced and in place. Power is transmitted with a further larger coil, much as in a wireless phone charger. This is picked up by a circuit in the snail, and used to power the LEDs inside.

It might not have been our first choice, but having seen it in action, we can’t deny a levitating 3D printed snail is pretty impressive. If you’d prefer something slightly more befitting such a high-tech looking presentation, perhaps a hovering SpaceX Starship would be more your speed.

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DEC’s LAN Bridge 100: The Invention Of The Network Bridge

August 27, 2024 by 13 Comments

DEC’s LAN Bridge 100 was a major milestone in the history of Ethernet which made it a viable option for the ever-growing LANs of yesteryear and today. Its history is also the topic of a recent video by [The Serial Port], in which [Mark] covers the development history of this device. We previously covered the LANBridge 100 Ethernet bridge and what it meant as Ethernet saw itself forced to scale from a shared medium (ether) to a star topology featuring network bridges and switches.

Featured in the video is also an interview with [John Reed], a field service network technician who worked at DEC from 1980 to 1998. He demonstrates what the world was like with early Ethernet, with thicknet coax (10BASE5) requiring a rather enjoyable way to crimp on connectors. Even with the relatively sluggish 10 Mbit of thicknet Ethernet, adding an Ethernet store and forward bridge in between two of these networks required significant amounts of processing power due to the sheer number of packets, but the beefy Motorola 68k CPU was up to the task.

To prevent issues with loops in the network, the spanning tree algorithm was developed and implemented, forming the foundations of the modern-day Ethernet LANs, as demonstrated by the basic LAN Bridge 100 unit that [Mark] fires up and which works fine in a modern-day LAN after its start-up procedure. Even if today’s Ethernet bridges and switches got smarter and more powerful, it all started with that first LAN Bridge.

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Building A Small Gyro Stabilized Monorail

August 27, 2024 by 10 Comments

Monorails aren’t just the core reason why The Simpsons remains on air after thirty-six seasons, twenty-six of which are unredeemable garbage. They’re also an interesting example of oddball rail travel which has never really caught on beyond the odd gadgetbahn project here and there. [Hyperspace Pirate] recently decided to investigate the most interesting kind of monorail of all—the gyro stabilized type—on a small scale for our viewing pleasure.

The idea of a gyro-stabilized monorail is to use active stability systems to allow a train to balance on a single very thin rail. The benefits of this are questionable; one ends up with an incredibly expensive and complex rail vehicle that must always run perfectly or else it will tip over. However, it is charming to watch in action.

[Hyperspace Pirate] explains how the monorail vehicle uses control moment gyroscopes to keep itself upright. The video also explains the more common concept of reaction wheels so the two systems can be contrasted and compared. It all culminates in a wonderful practical demonstration with a small 3D printed version of a 20th-century gyro monorail running on a 24″ track.

If you’re studying mechanical engineering this is a great project to pore over to see theoretical principles put into obvious practice. Video after the break.

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Hidden Gutter Antenna Keeps HOA Happy

August 27, 2024 by 140 Comments

The United States and a few other countries have an astounding array of homeowners’ associations (HOAs), local organizations that exert an inordinate influence on what homeowners can and can’t do with their properties, with enforcement mechanisms up to foreclosure. In the worst cases they can get fussy about things like the shade of brown a homeowner can paint their mailbox post, so you can imagine the problems they’d have with things like ham radio antennas. [Bob] aka [KD4BMG] has been working on tuning up his rain gutters to use as “stealth” antennas to avoid any conflicts with his HOA.

With the right antenna tuner, essentially any piece of metal can be connected to a radio and used as an antenna. There are a few things that improve that antenna’s performance, though. [Bob] already has an inconspicuous coax connector mounted on the outside of his house with an antenna tuner that normally runs his end-fed sloper antenna, which also looks like it includes a fairly robust ground wire running around his home. All of this is coincidentally located right beside a metal downspout, so all this took to start making contacts was to run a short wire from the tuner to the gutter system.

With the tuner doing a bit of work, [Bob] was able to make plenty of contacts from 10 to 80 meters, with most of the contacts in the 20 – 30 meter bands. Although the FCC in the US technically forbids HOAs from restricting reasonable antennas, if you’d rather not get on the bad side of your least favorite neighbors there are a few other projects from [Bob] to hide your gear.

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Using The Pi Pico As ‘Programmable Hardware’ For The Apple II

August 27, 2024 by 8 Comments

When we think of programmable hardware, we think of FPGAs. But they’re not the only option. [Oliver Schmidt] has been exploring how the Raspberry Pi Pico can serve in such a role for the classic Apple II. The talk was presented at the KansasFest event this year, and it’s well worth diving into!

[Oliver] has developed A2Pico. It’s a series of Apple II peripheral cards that are based around the Raspberry Pi Pico, as you might have guessed. [Oliver] has been working in the area since 2021 with one [Glenn Jones], with the duo experimenting with connecting the versatile microcontroller directly to the slot bus of the Apple II. [Ralle Palaveev] then chimed in, developing the A2Pico hardware with solely through-hole components for ease of assembly.

A number of cards have been developed based on A2Pico, including a storage device, a Z80 CP/M card, and a specialized card to play Bad Apple on the IIGS. It’s all thanks to the versatility of the programmable I/O (PIO) peripheral inside the Raspberry Pi Pico. This device enables the Pico to be reprogrammed to handle all sorts of complicated tasks at great speed. This is particularly useful when using it to bit-bang a protocol or talk with another machine, and it serves perfectly well in this role. Basically, by reprogramming the Pico and its PIO, the A2Pico design can become any one of a number of different add-on cards.

It’s well worth diving into this stuff if you’ve ever contemplated building your own peripheral cards for 8-bit and 16-bit machines. We’ve seen some other great add-on cards for vintage machines before, too.

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The Macintosh Plus Sounds Great If You Do Exactly This With It

August 26, 2024 by 3 Comments

The Macintosh Plus is not exactly known as particularly relevant in the worlds of chiptune or electronic music more broadly. That’s not to say it can’t do anything that sounds cool, however. As [Action Retro] demonstrates,  it’s got some really impressive tricks up its sleeve if you know what you’re doing.

The video centers around “Music Mouse”, a piece of software created by Laurie Spiegel for the Macintosh Plus all the way back in 1986. Spiegel saw the Macintosh Plus as a potential instrument for musical expression, with the then-innovative mouse as the key human interface.

[Action Retro] shows off the software, which is able to create rather pleasing little melodies with little more than a swish and a swash across the mousepad. The software makes smart use of scales so you’re not forever dodging around dissonant notes, so it’s quite easy to play something beautiful. He then makes things more interesting by pairing the Macintosh Plus with his favorite guitar pedal—the Old Blood Noise Endeavors Sunlight. It’s a dynamic reverb that really opens up the sonic landscape when paired with the Mac Plus. If you’re looking for a weird avant-garde setup to take on stage at your next noise show, this has to be it.

We’re usually used to seeing Nintendo and Commodore products in the retro computer music space. The Mac makes a nice change. Video after the break.

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