Sand Cast Banana for Scale is So Metal

If you’ve been on Reddit over the past year, you’ve likely encountered the “banana for scale” meme. [BFG121] felt that the size variation of bananas would not do – there needed to be a standard. He decided to make a metal banana out of re-purposed aluminum. He created his own furnace out of everyday objects including a hair dryer, metal bucket, cement, fire clay, and sand. [BFG121] used a typical banana as the reference for his sand casting mold. After melting the aluminum in his homemade furnace, he poured it into the empty mold, making sure there was an extra hole for the displaced air to escape. The end result is a perfect replica of a banana. [BFG121] made two aluminum bananas, and stamped each one with a serial number. One was given to Imgur headquarters while the other was auctioned on eBay. The winning bid (#39) was $67 USD, a very good ROI.

If you want to learn more about metal casting, check out myfordboy’s channel on YouTube.  You can also see an example of the “banana for scale” in this Hackaday article about a giant spirograph. Our only suggestion to [BFG121] is to send some to ASTM, NIST, and BIPM!

[via Reddit]

The Computeum, One Of The Biggest Computer Museums in Germany

QWERTZ Everywhere

I cannot say in words how perfect the venue for our Hackaday Munich party was. Not only was there a gigantic collection of vintage video games just around the corner, there was also a freaking warehouse full of mainframes, tubes, transistors, and some of the old retrocomputers you may have used in the 80s and 90s.

It’s called the Computeum, and without a doubt it is one of the most complete computer museums in Germany. There are fantastic computer museums in the states, but these don’t hold a candle to the pure amount of big iron and silicon found at the Computeum.

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[Ben Krasnow] Shows us How a Crookes Radiometer Works

[Ben Krasnow] is tackling the curious Crookes Radiometer on his Applied Science YouTube channel. The Crookes Radiometer, a staple of museum gift shops everywhere, is a rather simple device. A rotor with black and white vanes rotates on the head of a needle. The entire assembly is inside a glass envelope. The area inside the glass is not at a hard vacuum, nor is it filled with some strange gas. The radiometer only works when there is a partial vacuum inside.

The radiometer’s method of operation was long misunderstood. Sir William Crookes and James Clerk Maxwell both believed that the vanes moved due to the pressure of the photons hitting the vanes. If that were true though, the radiometer would spin in the opposite direction it normally does when held near a light source.  It was eventually discovered that the system is a thermodynamic one. [Ben] proves this by cooling down the radiometer’s glass with a can of freeze spray.  The radiometer immediately begins spinning backwards, with no light source present.

From there [Ben] mounts the rotor of a radiometer inside his vacuum chamber, which many will recognize as the chamber from his DIY electron microscope. As expected, the vanes don’t spin at a hard vacuum. In fact, [Ben] find the vanes spin fastest when the pressure is about 7 mTorr.

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Multi-target IDE for 8-Bit CPUs

A long time ago, [Martin] played with old 8-bit computers. Recently, he’s been honing his assembly skills again, and the idea of an IDE for a boatload of old systems came to him. After a year of work, he announced a multitarget IDE for 8-bit computers that works in your browser.

The project is called ASM80, and includes a code editor, a workspace to put all your code, compilers for the 8080/8085, Z80, 6502, 6800 and 6809 CPUs, emulators for all these CPUs, and emulators for a few Czech computers, the ZX Spectrum, and a few of [Grant Searle]’s single board computers.

What makes this project interesting is the syntax for all the different CPUs is pretty much the same. It’s a real, modular code editor that supports macros and everything you would expect for a code editor for ancient computers.

You can check out an assembler description here. [Martin] also has an offline, desktop-based version of ASM80 called IDE80, with a video demo of that below.

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Hand-Machined Companion Cube Can Be Destroyed and Rebuilt

[Michael Gainer] is a big fan of Portal, and it shows in the Weighted Companion Cube he made. [Michael] hand-machined the many pieces that comprise the Cube’s body and medallions out of 6061 aluminum. Dykem was used to transfer the marks for accurate machining, and the color is powder-coated to a heat tolerance of 400F. A CNC was used to make the distinctive hearts. [Michael] notes the irony was “very Portal” in having them cut by a heartless machine when everything else was done manually. The attention to detail is striking, the level of design more so when [Michael] proceeds to incinerate the poor Companion Cube with a brush burner. In the video shown at the link above, the Cube falls apart as the glue holding it together melts. When all is said and done, just grab more glue to bring that Cube back to its six-sided glory. Repeat to your heart’s content. Huge success! We have to be honest, after seeing all those pieces, we aren’t sure we’d want to do this very often. Companion Cubes have been featured in various iterations on Hackaday before, but they were never built with the idea of repeatedly destroying and rebuilding them. This novel take would make GlaDOS proud.

[Michael] has plans to put an Android device inside it with some light and temperature sensors. He wants to give it a voice resembling Portal’s turrets so it can whine when it needs to be charged or scream when it’s too hot or cold. He dubs this next project the “Overly Attached Weighted Companion Cube.” It wouldn’t be a good idea to incinerate this upcoming version, though we’d probably be inclined to if it demanded so much of our attention!

 

Teensys and Old Synth Chips, Together At Last

The ancient computers of yesteryear had hardware that’s hard to conceive of today; who would want a synthesizer on a chip when every computer made in the last 15 years has enough horsepower to synthesize sounds in software and output everything with CD quality audio? [Brian Peters] loves these old synth chips and decided to make them all work with a modern microcontroller.

Every major sound chip from the 80s is included in this roundup. The Commodore SID is there with a chip that includes working filters. The SN76489, the sound chip from the TI99 and BBC Micro are there, as is the TIA from the Atari consoles. Also featured is the Atari POKEY, found in the 8-bit Atari computers. The POKEY isn’t as popular as the SID, but it should be.

[Brian] connected all these chips up with Teensy 2.0 microcontrollers, and with the right software, was able to control these via MIDI. It’s a great way to listen to chiptunes the way they’re meant to be heard. You can check out some sound samples in the videos below.

Thanks [Wybren] for the tip.

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Wax Motors Add Motion to Your Projects

[electronicsNmore] has uploaded a great teardown and tutorial video (YouTube link) about wax motors. Electric wax motors aren’t common in hobby electronics, but they are common in the appliance industry, which means the motors can be often be obtained cheaply or for free from discarded appliances. Non-electric wax motors have been used as automotive coolant thermostats for years.  Who knows, this may be just what the doctor ordered for your next project.

As [electronicsNmore] explains, wax motors are rather simple devices. A small block of wax is sealed in a metal container with a movable piston. When heated, the wax expands and pushes the piston out. Once the wax cools, a spring helps to pull the piston back in.

The real trick is creating a motor which will heat up without cooking itself. This is done with a Positive Temperature Coefficient (PTC) thermistor. As the name implies, a PTC thermistor’s resistance increases as it heats up. This is the exact opposite of the Negative Temperature Coefficient (NTC) thermistors we often use as temperature sensors. PTC’s are often found in places like power supplies to limit in rush current, or small heating systems, as we have in our wax motor.

As the PTC heats up, its resistance increases until it stops heating. At the same time, the wax is being warmed, which drives out the piston. As you might expect, wax motors aren’t exactly efficient devices. The motor in  [electronicsNmore’s] video runs on 120 volts AC. They do have some advantages over solenoid, though. Wax motors provide smooth, slow operation. Since they are resistive devices, they also don’t require flyback diodes, or create the RF noise that a solenoid would.

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