Clever Reed Switch Catches Thief

January 8, 2014 by 58 Comments

When [Abhimanyu Kumar] noticed money going missing from his small bookshop, he decided to set up a little trap to catch the thief.

The problem was that the bookshop’s money was stored inside a cupboard in their house (back end of the shop), which meant that the culprit was likely one of their own employees. They already have a CCTV system installed in the actual store, and although he could simply add another camera in the house, [Abhimanyu] didn’t really want to do that.

He instead devised a simple security trap: dubbed the Jugaad Security System. In Hindi, Jugaad quite literally means “hack”. He added a small magnetic reed switch to the cupboard where the money is stored—well, was stored—which is then linked directly to an intervalometer. This then connects to an inconspicuous DSLR sitting on one of the work benches. He aimed the camera at the cupboard and, in case the lights are out when the system is tripped, set it to an extremely high ISO.

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Porting Contiki To The TI MSP430 Launchpad

January 7, 2014 by 16 Comments

For many years Contiki has been one of the main choices when it came to choosing an IPv6 over Low power Wireless Personal Area Networks stack (aka 6LoWPAN). It is developed by a world-wide team of developers with contributions from Atmel, Cisco, ETH, etc… and is open source. As most platforms to which Contiki has been ported are quite expensive, [Marcus] decided to bring the operating system to the TI Launchpad. For our readers that don’t know, the latter is based on a msp430g2452/2553 microcontroller, which only have 256/512 bytes of RAM and 16kB of ROM. As a side note, Contiki typically requires 10k RAM and 30k ROM.

[Marcus] therefore had to remove several features from Contiki: queue-buffering, energy estimation and regrettably uIP. His test setup (shown above) uses the TI CC2500 radio that can be found for less than $2 on Aliexpress, for which he wrote radio drivers from scratch. He also coded his own radio duty-cicling layer, as the one included in Contiki was too big.

Paintball Pistol Turned Sniper Rifle

January 7, 2014 by 43 Comments

OBXP6G7

There’s a huge price discrepancy between paintball pistols and paintball sniper rifles. So the [Fresh-Prints-of-3D] decided to print himself an sniper upgrade kit.

He started with the classic Tippman 98 Custom pistol , which is a tried and true industry standard when it comes to reliable paintball guns. Using Sketchup he designed a side loading hopper adapter, a fixed stock, a magazine adapter, various brackets, and even a bipod fore-grip. He then printed the parts out at his local hackerspace; Innovatrix Labs, which is in Northeastern Pennsylvania. A Portabee 3D printer was used for some of the first prototypes but the final parts were all printed on a large MendleMax2 which has a build area large enough for the entire fixed stock!

The best part? He’s only been using SketchUp for a few months. Once the design and build is completely finalized he might release it under a CC license. 

It just goes to show that 3D printers are really breaking down various markets of overpriced plastic components — 3D printers only print trinkets? Pfft.

[Via Reddit]

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.

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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!

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