The First Radio Sets: a Spark Gap and a Coherer

[Ashish] let us know about his experiments in recreating the earliest type of radio set: a spark-gap transmitter and iron-filings coherer. He goes through the historical development of the kit in great detail, so we’re just going to skip that part. Go read it yourself!

Instead, we’re going to tease you with the coolest part of the rig: the coherer. In [Ashish]’s build, it’s a piece of tubing with some iron filings between two bolts. When a sufficiently strong EM wave hits the filings, they stick together and bridge the gap between the bolts, allowing electricity to flow and light up an LED, for instance. You can see this in [Ashish]’s video below the break, along with kmore discussion of that coherer.

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Bicycle-Powered Wimshurst Machine

A lot of great pieces of real technology were inspired (or, at least, look like) pieces of technology from science fiction of the past. Like the smartphones of today have a surreal resemblance to the Star Trek communicators of the 60s, [Steve] took inspiration from a story about a bicycle racing in space and set out to make his own.

In the story, the bicycle wheels are replaced by electrostatic generators that power a type of (fictional) ion drive. Since an ion drive wouldn’t add much thrust to a bicycle operated on the Earth, [Steve] used the electrostatic generator he built to create a sparking light show. The generator is called a Wimshurst machine and has two counter-rotating discs which collect charge. The charge is dissipated across a spark gap which is placed where the bike light would normally go.

We don’t know if the sparks from the Wimshurst generator are enough for a proper headlight, but it’s definitely a cool effect. [Steve] also points out that it might also work as a bug zapper, but either way you should check out the video after the break to see it in action! While it’s not quite a tricorder it’s still a pretty impressive sci-fi-inspired build, and something that’s definitely unique in the bicycle realm.

There’s quite a collection of these Wimshurst projects beginning to come together. Here’s one made using a trio of soda bottles, and another example which used 3D printing.

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[Mehdi’s] Shocking Stun Gun Tutorial

[Mehdi Sadaghdar] never lets little things like fire, shocks, or singed fingers get in the way of his projects.  His latest is a tutorial on making a simple electroshock device. A stun weapon creates a very high voltage, and is used in law enforcement to temporarily disable a person. [Mehdi] stresses repeatedly to not use this on anyone. If you do, he won’t like you anymore. Of course, if you’ve seen any of his previous videos, you know he’ll shock himself and set something on fire before the project is complete.

To create his stunner, [Mehdi] used a car ignition to produce a high voltage. The igniton coil, which is a specialized transformer, allowed him to generate the >10000V output needed for the stunner. The coil has a 60:1 ratio and is powered by a 12V DC supply. Since a coil is a short at DC, the system only creates a high voltage pulse when power is disconnected. However, the pulse was too short to create a satisfying arc. [Mehdi] added a capacitor, creating an LC circuit that oscillates as the charge decays, creating a nicer spark. He then used an RC circuit and a relay to create a simple oscillating switch. For the finishing touch, he created a spark gap on the secondary of the transformer with two nails. In typical [Mehdi] fashion, he nearly fried his digital caliper in the process.

The end result is a nice spark that warms the cockles of [Mehdi’s] fibrillating heart. We commend him for being such a brave masochist in the name of science.  Check out his tutorial after the break!

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Copper vapor laser is amazing

What better way to spend a few months in the workshop than by heating Copper chloride to 400° C, building rotary spark gaps and 30kV capacitors, playing with high vacuums and building a very powerful laser? It’s just a day in [Jon]’s life as he builds a DIY Copper vapor laser.

Copper vapor lasers require temperatures of about 1500° C, but this is only when using pure Copper. Compounds such as Copper chloride are able to bring the required temperatures for lasing down to about 400° C, a reasonable temperature for [Jon]’s home built laser tube furnace. The only problem with this setup is the requirement for two electrical pulses, one to disassociate the Copper and a second to make the Copper lase.

The professional way of creating these electrical pulses would be a Thyratron, but it seems [Jon] wanted something cooler. He built a rotary spark gap out of two 2 inch thick blocks of acrylic that allow him to perfectly time the frequency and separation of the electrical pulses needed for his laser.

There is no word on exactly how much power [Jon]’s Copper vapor laser will put out when it’s complete, but [Jon]’s build log is already an amazing display of awesome. You can check out a short video showing off [Jon]’s laser, spark gap, and huge home-made capacitor after the break.

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Tesla coil bullet-time photography


One thing we can all probably agree on is that Tesla coils are one part high-voltage electricity and two parts pure awesome. [Rob Flickenger] thinks so too, and he built a pretty nice one in his workshop some time ago. He took a bunch of pictures showing off the coil’s capabilities, but he thought that one photo taken from a single angle didn’t do much to relay just how fantastic it is to watch a Tesla coil in action.

Taking a cue from the Matrix movies, he bought a stack of Canon point and shoot cameras and constructed a bullet time rig in his workshop. In order to get the pictures just right, he flashed each camera with a customized version of the CHDK firmware that allowed him to trigger all ten shutters with a single button press. A few scripts help facilitate collecting all of the images for processing, after which he identifies the good shots and stitches them together. You can see the awesome results in the video below.

[via LaughingSquid]

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Jacob’s Ladder


[jandgse812] shows us how to build a Jacob’s Ladder from mostly household parts.   The bulk of the instructions for this project are included in the downloadable document, there is a downloadable video as well. Be sure to follow to the end where he shows us a much safer and possibly better looking revision. The Jacob’s Ladder has become standard fair for any mad scientists laboratory. If you plan on having a workshop suited for world domination, it absolutely must have one of these in it. Be careful though, the high voltage can be deadly.