Homebrew Analog Scope Project Log

September 1, 2015 by 7 Comments

[GK] had some old CRTs lying around, so naturally he decided to build an old school analog scope with one of them. Lucky for us, he’s been documenting his progress. Since it was a big project to tackle, he started out with Spice modeling to work out all the right values.

Prototyping the power supply took some custom transformer winding, but when done, the power supply did the job. Although he’s still wiring up the Z (intensity) axis, the scope is already capable of displaying signals and even text characters using a character generator he built earlier (see video below).

[GK] spends most of the time so far talking about the high voltage power supply design. For the particular tubes he had on hand he needed +200V, -400V, -550V, and 6.3VAC for the CRT heater. This is certainly not the typical Arduino-based digital scope that everyone builds at least once.

We love analog scopes for art projects, logic analyzer conversions, and gaming. Of course, if you don’t have an old CRT in your parts bin, you might consider trying a laser.

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atom drawing

The Eulogy Of Local Hidden Variables

September 1, 2015 by 51 Comments

During the early 1900’s, [Einstein] was virtually at war with quantum theory. Its unofficial leader, [Niels Bohr], was constantly rebutting Einstein’s elaborate thought experiments aimed at shooting down quantum theory as a description of reality. It is important to note that [Einstein] did not disagree with the theory entirely, but that he was a realist. And he simply would not believe that reality was statistical in nature, as quantum theory states. He would not deny, for example,  that quantum mechanics (QM) could be used to give a probable location of an electron. His beef was with the idea that the electron doesn’t actually have a location until you try to measure it. QM says the electron is in a sort of “superposition” of states, and that asking what this state is without measurement is a meaningless question.

So [Einstein] would dream up these incredibly complex hypothetical thought experiments with the goal of showing that a superposition could not exist. Now, there is something to be said about [Einstein] and his thought experiments. He virtually dreamed up his relativity theory while working as a patent clerk at the ripe old age of 26 years using them. So when he had a “thought” about something, the whole of the scientific world stopped talking and listened. And such was the case on the 4th of May, 1935.

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Arduino Video Over 2 Wires For Under $50: Mesa-Video

September 1, 2015 by 60 Comments

If you want video support on your project, you might start from a device like a Raspberry Pi that comes with it built in. [Kevinhub88] doesn’t accept such compromises, so he and his Black Mesa Labs have come up with a whole new way to add video support to devices like the Arduino and other cheap controllers. This project is called Mesa-Video, and it can add digital video at a resolution of up to 800 by 600 pixels to any device that has a single serial output.

The video is created by an FT813, a low cost GPU from FTDI that offers a surprising amount of video oomph from a cheap, low power chip (he has demoed it running from a lemon battery), meaning that he is hoping to be able to sell the Mesa-Video for under $50.

UPDATE: [KevinHub88] let us know that he didn’t actually power the device from a lemon battery, as you would need a lot of lemons to make 50mA at 5V. Apologies for any confusion!

However, Mesa-Video is just the beginning. [Kevinhub88] wanted to get around the problem of stacking shields on Arduinos: add more  than one and you get problems. He wanted to create an interface that would be simpler, faster and more open, so he created the Mesa-Bus. This effectively wraps SPI and I2C traffic together over a simple, fast serial connection that doesn’t require much decoding. This means that you can send power and bi-directional data over a handful of wires, and still connect multiple devices at once, swapping them out as required. You could, for instance, do your development work on a PC talking to the prototype devices over Mesa-Bus, them swap the PC out for an Arduino when you have got the first version working in your dev environment. Is the Arduino not cutting it? Because Mesa-Bus is cross-platform and open source, it is easy to swap the Arduino for a Raspberry Pi without having to change your other devices. And, because all the data is going over a simple serial connection in plain text, it is easy to debug.

It’s an ambitious project, and [Kevinhub88] has a way to go: he is currently working on getting his first prototype Mesa-Bus devices up and running, and finalizing the design of the Mesa-Video. But it is an impressive start and we’ll be keeping a close eye on this work. Hopefully he can avoid that head crab problem as well because those things are as itchy as hell.

RC Lawnmower Has No Grass To Cut

August 31, 2015 by 18 Comments

They say laziness and necessity is one of the greatest drives for invention. Whoever said that didn’t think about what happens when inventors are bored. [The Random Mechanic] decided to build himself a remote-controlled lawnmower, despite the terrible drought he’s been having — resulting in literally no grass to cut.

To make the lawn mower remote-controlled, he cobbled together a gas lawn mower, with the remains of an electric wheelchair. This ended up working really well. He’s using an old RC car remote and its two servos to remotely control the original wheel chair’s joystick. Simple, but super effective.

The wheelchair mower is fast, nice and heavy thanks to some lead acid batteries, and very maneuverable with the front wheels being casters. It’s a shame he doesn’t have any grass to cut!

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Custom Threaded Inserts For 3D Printing

August 31, 2015 by 29 Comments

There’s a variety of ways to add threaded holes to 3D printed objects. You can tap a hole, but the plastic isn’t always strong enough. Nut traps work, but aren’t very attractive and can be difficult to get exactly the right size. If you try to enclose them, you have to add a manual step to your printing process, too. You can buy threaded inserts (see video below) but that means some other piece of hardware to have to stock in your shop.

[PeterM13] had a different idea: Cut a piece of threaded stock, put nuts on the end and heat it up to let the nuts reform the plastic. This way the nut traps wind up the perfect size by definition. He used two nuts aligned and secured with thread locker. Then he used a hot air gun to only heat the metal (so as to reduce the chance of deforming the actual part). Once it was hot (about 15 seconds) he pulled the nuts into the open hole, where it melted the plastic which grips the nuts once cooled again.

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Liquid Metal Changes Shape To Tune Antenna

August 31, 2015 by 39 Comments

Antennas can range from a few squiggles on a PCB to a gigantic Yagi on a tower. The basic laws of physics must be obeyed, though, and whatever form the antenna takes it all boils down to a conductor whose length resonates at a specific frequency. What works at one frequency is suboptimal at another, so an adjustable antenna would be a key component of a multi-band device. And a shape-shifting liquid metal antenna is just plain cool.

The first thing that pops into our head when we think of liquid metal is a silvery blob of mercury skittering inside the glass vial salvaged out of an old thermostat. The second image is a stern talking-to by the local HazMat team, so it’s probably best that North Carolina State University researchers [Michael Dickey] and [Jacob Adams] opted for gallium alloys for their experiments. Liquid at room temperature, these alloys have the useful property of oxidizing on contact with air and forming a skin. This allows the researchers to essentially extrude a conductor of any shape. What’s more, they can electrically manipulate the oxidative state of the metal and thereby the surface tension, allowing the conductor to change length on command. Bingo – an adjustable length antenna.

Radio frequency circuits aren’t the only application for gallium alloys. We’ve already seen liquid metal 3D printing with them. But we need to be careful, since controlling the surface tension of liquid metals might also bring us one step closer to this.