Author: Al Williams

4349 Articles

15 Volts To 110,000 Volts

December 14, 2020 by 25 Comments

There’s something satisfying about creating high voltages. Sure, there are practical uses like neon signs or doing certain experiments, but be honest — you really just want to see some giant arcs lighting up your dark mad scientist lair. [Mircemk] has just the prescription for what ails you. Using a two-stage approach, he shows a simple setup that generates about 110KV from a pretty tame 15V supply.

From the 15V, there is a stage that uses a flyback transformer and a switch to generate a reasonably high voltage. The final stage is a Cockroft-Walton voltage multiplier that can produce quite a bit of voltage. You can see the impressive arcs in the video below.

The multiplier circuit found fame with experiments by Cockroft and Walton, obviously, but was actually originated in the early 1900s with a physicist named Greinacher. The circuit uses diodes as switches and charges a bank of capacitors in parallel. The discharge, however, puts the capacitors in series. Neglecting losses and loads, the output voltage is equal to the peak-to-peak input voltage times the number of stages present. Real-world considerations mean you won’t quite get that voltage out of it, but it can still provide a potent punch. Click through the break for a video of the circuit in action!

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Creality WiFi Takes On Octoprint

December 13, 2020 by 78 Comments

A very common hack to a 3D printer is to connect a Raspberry Pi to your printer and then load Octoprint or a similar program and send your files to the printer via the network. [Teaching Tech] noticed that Creality now has an inexpensive WiFi interface that promises to replace Octoprint and decided to give it a quick review.

You might wonder why you’d want this system when Octoprint exists? Mainly, the value proposition is the price. You can buy the Creality box for about $20. A Raspberry Pi with a similar case would be at least twice that price. In addition, the box integrates with a Thingiverse-like library and does cloud slicing, which is attractive when you have a very small computer connected to your printer.

However, [Teaching Tech] found some issues. The box was pretty picky about connecting to printers and there were many other problems. The 3D model library wasn’t very comprehensive, although that could change if the thing got very popular. Worse, the slicer didn’t really produce stellar results.

We have to admit, an attractive network interface for $20 would be of interest. But it is hard to see how this would be a better value than Octoprint unless you were very short on cash and had no Raspberry Pi surplus laying around. You still need an SD card and a power supply, so those extras are a wash.

On the other hand, if Creality fixes the problems and expands the 3D model library, we’d buy one. But it remains to be seen if either of those things will happen, much less both of them. We do wish [Teaching Tech] had opened the thing up for us. Maybe next time.

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Surfing The Web With 7400 Logic

December 11, 2020 by 12 Comments

We see more computers built from logic gates than you might expect. However, most of them are really more demonstration computers and can’t do much of what you’d consider essential today. No so with [Alastair Hewitt’s] Novasaur. Although built using 34 TLL chips (and a few memory and analog chips, too, along with one PAL), it boasts some impressive features:

  • Dual Processor CPU/GPU (Harvard Architecture).
  • 33 MHz dot clock, 16.5 MHz data path, 8.25 MHz per processor (~3.5 CPU MIPs)
  • 256k ROM: 96k ALU, 64k native program, 64k cold storage, 32k fonts.
  • 128/512k RAM: 1-7 banks of 64k user, 60k display, 4k system.
  • 76 ALU functions including multiply/divide, system, and math functions.
  • Bitmapped Graphics: Hi-res mode up to 416×240 with 8 colors and 4 dithering patterns. Lo-res mode up to 208×160 with 256 colors, double-buffered.
  • Text Mode: 8 colors FG/BG, 256 line buffer, up to 104×60 using 8×8 glyphs, 80×36, and 64×48 rows using  8×16 glyphs.
  • Audio: 4 voice wavetable synthesis, ADSR, 8-bit DAC, 8Hz-4.8kHz.
  • PS2 Keyboard: Native interface built-in.
  • RS232 Serial Port: Full duplex, RTS/CTS flow control, 9600 baud.
  • Expansion Port: 7 addressable 8-bit register ports, 4 interrupt flags

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A Thousand Feet Under The Sea

December 11, 2020 by 15 Comments

If you were to plumb the depth of the oceans, you could only get so far with a snorkel or a SCUBA tank. We don’t know the price, but if you have enough money, you might consider the Triton 3300/6 — a six-person submersible that can go down to 3,300 feet (hence the name–get it–3300/6). Billed as “diving for the entire family,” we aren’t sure we can load grandma and the kids in something like this, but that doesn’t mean we wouldn’t like to try.

The machine can carry up to 1,760 pounds and can make 3 knots which isn’t going to set any speed records. At around 24,000 pounds, the two main thrusters are lucky to make that speed. The view bubble is apparently optically perfect acrylic made by a German company and the company claims the 100-inch diameter bubble is the world’s largest spherical acrylic pressure hull.

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A Lambda 8300 Lives Again

December 10, 2020 by 3 Comments

If you follow retrocomputing — or you are simply old enough to remember those days — you hear the same names over and over. Commodore, Apple, Radio Shack, and Sinclair, for example. But what about the Lambda 8300? Most people haven’t heard of these but [Mike] has and he has quite a few of them. The computer is similar to a Sinclair ZX81, but not an exact clone. All of his machines need some repairs (he’s promised repair videos are on their way), but for the video below he wired a monitor directly to the PCB to get steady output, so apparently the RF modulator is the failing subsystem in this case.

Once the video cleared up, you can see a walkthrough of running a simple BASIC program. As was common in those days, the computer used an audio cassette recorder for data storage. [Mike] picked up some dedicated recorders meant for computer use, but neither were in working shape. However, a consumer player works fine.

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Easy Frequency Counter Looks Good, Reads To 6.5 MHz

December 10, 2020 by 12 Comments

We were struck by how attractive [mircemk’s] Arduino-based frequency counter looks. It also is a reasonably simple build. It can count up to 6.5 MHz which isn’t that much, but there’s a lot you can do even with that limitation.

The LED display is decidedly retro. Inside a very modern Arduino Nano does most of the work. There is a simple shaping circuit to improve the response to irregular-shaped input waveforms. We’d have probably used a single op-amp as a zero-crossing detector. Admittedly, that’s a bit more complex, but not much more and it should give better results.

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Inside CHIP-8

December 7, 2020 by 4 Comments

Certain old computers — most frequently those using the RCA 1802 — were fond of using an early form of byte-code interpreter for programs, especially games. The interpreter, CHIP-8, was very simple to create but offered high-level features that were tedious to recreate in the native assembly language. Because there are a fair number of simple games written in CHIP-8, there are of course, emulators for it, and [River Gillis] decided to look inside the CHIP-8 byte code interpreter.

Part of the power of CHIP-8 was it only had 35 virtual instructions. That was important when you were trying to shoehorn a game and the interpreter into a very small memory. Remember, in those days 1K of memory wasn’t an unusual number, although the prototypical CHIP-8 host would have 4K.

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