Homemade Polariscope Is Super Easy To Make

January 7, 2014 by 6 Comments

polariscope

[Abhimanyu Kumar] was watching YouTube videos one day when he came across something called a Polariscope — After learning how it worked, he discovered you can make your own using household items!

First off, what is a Polariscope? Well, put simply, it is a device that can show you the photoelasticity of a clear specimen, which can reveal the stress distribution in the material! And it is actually really easy to make one.

All you need to build your own is:

  • A polarized light source (any modern LCD monitor)
  • A transparent specimen (plastic cutlery, glass statues, plastic you can bend, etc)
  • A circular polarizing filter (the cheap 3D glasses you didn’t return at the theater)

Then just place the objects in the order shown in the diagram and start snapping some photos. This would be really cool for checking stress concentrations in a project — provided you are using some Lexan or acrylic!

Controlling Cheap, Awesome Christmas Lights

January 7, 2014 by 13 Comments

LEDs

[James] was wandering around Walgreens after Christmas and found something very interesting – RGB LED Christmas lights that were individually addressable. At $6.50 for a strand of 15 lights, he just had to buy a few and figure out the control protocol. After all, who can turn down a big, cheap, controllable RGB LED strip?

The packaging for these lights – apparently manufactured by BriteStar – includes a ‘try me’ button that cycles through different light patterns. This button is what initially tipped [James] off to the fact the lights on this strand could be individually controllable. Opening up one of the lights, he found exactly what he wanted: an epoxy blob, two wires for power, and three wires for the signaling.

After checking out this light with a scope and logic analyzer, [James] realized there was a very, very simple protocol going on. Essentially, the entire string functioned as a gigantic shift register, taking the values for one light and pushing it down the string. In looking at the protocol, [James] also discovered] these lights support 16 levels of brightness. Yep, RGB LED Christmas Lights with PWM for under $7. Can’t beat that.

[James] wrote an Arduino library to control these strings and put it up on Github. While your local Walgreens has probably already hidden these lights away in the back of the store, it might be worth asking around to see if they have any left.

Retrotechtacular: Tube Amplifiers

January 7, 2014 by 28 Comments

retrotechtacular-how-tube-amps-work

It’s hard to beat this vintage reel for learning about how vacuum tube amplifiers work. It was put together by the US Army in 1963 (if we’re reading the MCMLXIII in the title slide correctly). If you have a basic understanding of electronics you’ll appreciate at least the first half of the video, but even the most learned of radio enthusiasts will find something of interest as they make their way through the 30-minute presentation.

The instruction begins with a description of how a carbon microphone works, how that is fed to a transformer, and then into the amplifier. The first stage of the tube amp is a voltage amplifier and you’ll get a very thorough demo of the input voltage swing and how that affects the output. We really like it that the reel discusses getting data from the tube manual, but also shows how to measure cut-off and saturation voltage for yourself. From there it’s off to the races with the different tube applications used to make class A, B, and C amplifiers. This quickly moves onto a discussion of the pros and cons of each amplifier type. See for yourself after the jump.

Continue reading “Retrotechtacular: Tube Amplifiers” →

Delta Laser Engraver Uses Inkscape For G-Code

January 7, 2014 by 18 Comments

lazer

[Z LeHericy] has a SeeMe CNC Rostock Max 3D printer, and a 2W WickedLasers Spyder Artic blue laser. Naturally, he had to try strapping them together.

Most of our homemade laser engravers featured here use recycled DVD burner diodes, and while they certainly work, they leave a bit to be desired… Well, if you want more power, let us introduce the Class 4 Artic Spyder 2W blue laser from WickedLasers — a company that sells super high-powered lasers to anyone who can afford them — because that’s a great idea!

Safety concerns aside — wear your darn laser goggles! This pair can etch wood and leather quite well. He’s been using it to etch celtic knots onto pieces of leather. To do this he’s used Inkscape to convert a .BMP of the knot into a vector image, and then using the G-Code tools included with Inkscape he can create a tool path for the printer.

The finished leather looks awesome — Stick around after the break to see the laser in action!

Continue reading “Delta Laser Engraver Uses Inkscape For G-Code” →

Acoustic Delay Line Memory

January 7, 2014 by 48 Comments

Back in the olden days  when computers were both analog and digital, making RAM was actually very hard. Without transistors, the only purely electronic means of building a memory system was vacuum tubes; It could have been done, but for any appreciable amount of RAM means an insane amount of tubes, power, and high failure rates.

One of the solutions for early RAM was something called a delay line. This device used ultrasonic transducers to send a pulse through a medium (usually mercury filled tubes heated to 40°C) and reads it out at the other end. The time between the pulse being sent and received is just enough to serve as a very large, small capacity RAM.

Heated tubes filled with hundreds of pounds of mercury isn’t something you’d want sitting around for a simple electronics project. You can, however, build one out of a Radio Shack Electronics Learning Lab, a speaker, and a microphone.

[Joe] designed his delay line using an op-amp to amplify the train of acoustic pulses traveling through the air. A compactor picks up these pulses and sends them into a flip-flop. A decade counter and oscillator provide the timing of the pulses and a way to put each bit in the delay line. When a button on the electronics lab is pressed, a ‘tick’ is sent into the speaker where it travels across [Joe]’s basement, into the microphone, and back into the circuit.

The entire setup is able to store ten bits of information in the air, with the data conveniently visualized on an oscilloscope. It’s not a practical way to store data in any way, shape, or form, but it is an interesting peek into the world before digital everything.

Video below.

Continue reading “Acoustic Delay Line Memory” →

Intel Edison: A Desktop From 1998 In An SD Card

January 7, 2014 by 86 Comments

According to the barrage of press releases hitting the Hackaday tip line, the Consumer Electronics Show is upon us with announcements of amazing new technologies such as jackets with a cell phone pocket, alarm clocks with Bluetooth, and iPhone cases with a kickstand. What an age to live in.

Among the more interesting announcements at CES is the Intel Edison, a tiny device that combines a dual core Intel SoC with ‘a Pentium instruction set’, WiFi and Bluetooth adapter, and some amount of storage into an SD card form factor. Apart from that, little else is known about the Intel Edison and the only other primary source for this announcement appears to be Intel CEO [Brian Krzanich]’s CES keynote address.

The Edison will be able to run Linux, ‘other operating systems’, and will support Wolfram, the Mathematica-esque programming language where everything is a data type. Edison will also have an app store. Because that’s a thing now, apparently.

If you can’t wait for Edison to be released sometime in the middle of 2014, we’d suggest you check out the Intel Galileo. It’s an Arduino compatible board based on the same Quark SoC found in the Edison but in a significantly more convenient form factor. The Galileo doesn’t have on board WiFi or Bluetooth, but at least you don’t have to wait for the release of the Edison and the complications of a purpose-built breakout board for whatever application you’re thinking of.

Keeping The Family Off The Net With An Undocumented Backdoor

January 6, 2014 by 33 Comments

memetics

When [Eloi] was home for Christmas, he faced one of the most difficult problems man has ever faced: his entire family, equipped with smartphones and laptops, siphoning all the Internet through a 1Mb/s connection. For any technically minded person, the fix for this problem is to limit the bandwith for all those Facebook and Twitter-heads, while leaving [Eloi]’s battlestation unaffected. [Eloi] had originally set up the Linksys WAG200G router in the family home a few years ago but had since forgotten the overly complex admin password. No worries, then, because apparently the WAG200G is open as wide as a barn door with a completely undocumented backdoor.

Without the password to the admin panel of the router, [Eloi] needed a way in. After pointing nmap at the router, he found an undocumented service running on port 32764. Googling this observation resulted in a lot of speculation, so the only option was to download the router’s firmware, look for the service, and figure out a way in.

[Eloi] eventually got a shell on the router and wrote a very short Python script to automate the process for all WAG200G routers. As for where this backdoor came from, it appears a SerComm device on the router is responsible. This means a whole bunch of routers with this specific SerComm module also have this backdoor, and we’d assume anything with a service running on port 32764 is suspect.

If you’re looking for a fix for this backdoor, your best bet is probably installing OpenWRT or Tomato. The OpenWAG200 project, an open firmware specifically designed for [Eloi]’s router, still has this vulnerability, though.