Relays Calculate Square Roots

After seeing an exhibit of an old relay-based computer as a kid, [Simon] was inspired to build a simple two-relay latching circuit. Since then, he’s been fascinated by how relays can function to do computation. He’s come quite a long way from that first latching circuit, however, and recently finished a huge five-year project which uses electromechanical relays to calculate square roots.

DSC_0240-e1394580570356

The frame of the square root calculator can hold up to 30 identical relay modules, each of which hold 16 relays on PCBs, for a total of 480 relays. The module-based setup makes repair and maintenance a breeze. Numbers are entered into the computer by a rotary dial from an old phone and stored in the calculator’s relay memory. A nixie tube display completes the bygone era-theme of the device and shows either the current number that’s being entered, or the square root of that number as it’s being calculated.

The real magic of this project is that each relay has an LED which illuminates whenever the relay is energized, which shows the user exactly where all of the bits of the machine are going. [Simon] worked on this project from 2009 and recently completed it in 2014, and it has been featured at the San Mateo Maker Faire and at Microsoft Research in Redmond, WA. We’ve seen smaller versions of this before, but never on this scale and never for one specific operation like square roots.

Video below. Thanks to [Bonsaichop] for the tip!

Continue reading “Relays Calculate Square Roots”

Low-Voltage Tesla Coil Uses a Relay Instead of a Spark Gap

[Teodor] writes in with a unique Tesla coil he designed and built. Unlike most Tesla coils, [Teodor]’s design is able to run with a fairly low input voltage because it doesn’t use a static spark gap like most Tesla coils. Instead, his coil uses a relay in place of a spark gap.

[Teodor] built his coil using leftover components from his old school, making good use of some parts that might have otherwise been thrown away. The most critical component of his circuit, the relay, is just a standard normally-closed relay that is rated at 20A. [Teodor] wired the relay so that it energizes its own coil whenever it is shut. This causes the relay to briefly open every time the coil is energized, creating a resonant circuit. The resonant circuit charges a tank capacitor and places it in series with the primary coil inductor every time the relay closes, forming the tank circuit of his design.

With [Teodor]’s design, the resonant frequency of the secondary is nearly identical to that of the primary. This creates a significant voltage boost, helping produce very high voltages from such a low input voltage. The only downside to this design that [Teodor] recently discovered is that the relay contacts get red-hot after a few minutes of operation. Not optimal, but it still works! Check out [Teodor]’s writeup for more details and instructions on how to build your own.

Making Something Useful With The ESP8266

The ESP8266 is the latest and greatest way to get a project connected to the Internet, but so far we haven’t seen many projects that actually do something with this very cool chip. Yes, there are a few people pinging away with AT commands, and there is a thriving community building interpreters and flashing new code on this chip, but not much in the way of actual projects. [Martin] is the exception. He’s come up with two projects that use the ESP8266.

The first project is one that puts the readings from a DHT22 temperature/humidity sensor up on the Internet. Following the spirit of all the recent development of the ESP8266, [Martin] isn’t using an external microcontroller. Instead, he’s using the SDK to run an HTTP daemon using [Sprite_TM]’s code. This web server provides an interface to turn an LED on and off, and reports the temperature and humidity readings from the DHT22. It’s simple, but it’s easy to see how this tiny chip could become the basis for a smart thermostat.

If lighting up LEDs isn’t enough, [Martin] has another project that includes three solid state relays. This one is a bit more complex with MQTT support, a fancy jQuery interface, and support for network time. [Martin] isn’t quite ready to publish the complete code for this project, but that’s only because there are a few features he’d like to implement before making it public. These include dynamic DNS, scheduling functionality, and support for an I2C status display. Even without these fancy features, it’s still a great project that’s still extremely capable for an Internet of Things thing. You can check out [Martin]’s video demo of this board below.

Continue reading “Making Something Useful With The ESP8266″

[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!

Continue reading “[Mehdi’s] Shocking Stun Gun Tutorial”

Pwning Timberman with Electronically Simulated Touchscreen Presses

arduino-plays-timerman

What do you do if you suck at a smartphone game? Buy some in-game upgrades to pretend like you’re good? Screw that! [Valentin] did what any self-respecting hacker would: developed an automated system to play for him.

Granted, when you see the demo video embedded below you’ll realize there isn’t much strategy involved in this game. But that setup to simulate the touchscreen presses is pretty neat. We’re used to seeing mechanical touchscreen hacks but this one is electronic, using a couple of pads of copper foil tape and some relays to make it happen. Here’s the one caveat: you still need to be touching something with your hand. This just uses the relays to switch the connection between the pads and your body.

We’ve looked around for this before. Does anyone have a cheap, simple, and effective hack to fully automate presses on a modern touchscreen? Can we use a potato or something? Tell us below, but send it in to the tips line too!

Continue reading “Pwning Timberman with Electronically Simulated Touchscreen Presses”

Quick and Dirty RFID Door Locks Clean up Nice

homemade RFID Door Locks

[Shawn] recently overhauled his access control by fitting the doors with some RFID readers. Though the building already had electronic switches in place, unlocking the doors required mashing an aging keypad or pestering someone in an adjacent office to press a button to unlock them for you. [Shawn] tapped into that system by running some wires up into the attic and connecting them to one of two control boxes, each with an ATMega328 inside. Everything functions as you would expect: presenting the right RFID card to the wall-mounted reader sends a signal to the microcontroller, which clicks an accompanying relay that drives the locks.

You may recall [Shawn’s] RFID phone tag hack from last month; the addition of the readers is the second act of the project. If you’re looking to recreate this build, you shouldn’t have any trouble sourcing the same Parallax readers or building out your own Arduino on a stick, either. Check out a quick walkthrough video after the jump.

Continue reading “Quick and Dirty RFID Door Locks Clean up Nice”

The Relay-Based Mouse Emulator

mouse

[Nixie]’s job involves using some test software that requires moving a mouse around, clicking a few buttons, checking if everything is okay, and repeating the process over and over again. This is obviously a solution for some keyboard macros, but in a fit of sadistic spite, the test software requires someone to move a mouse around the screen. What is [Nixie] to do? Make a mouse emulator and automate the whole thing, of course.

The Memulator, as [Nixie] calls the device, is the latest in a series of devices to increase productivity when testing. The first version was the mouse tumor, an odd-looking device that simply switched off the LED for an optical mouse, keeping the cursor in one spot while [Nixie] hammered a button repeatedly. The second version is more advanced, capable of moving the cursor around the screen, all without doing an iota of USB programming: [Nixie] is simply using a resistive touch pad, some relays and a few pots to turn buttons into cursor movements. It’s such a simple solution it almost feels wrong.

There’s some interesting tech here, nonetheless. For some reason, [Nixie] has a few cases of old, can-shaped soviet-era relays in this build. While using such cool, awesome old components in such a useful and productive build seems odd, if you’re trying to fix ancient software that’s so obviously broken, you might as well go whole hog and build something that will make someone in twenty years scratch their head.

Vertical video of the Memulator below.

Continue reading “The Relay-Based Mouse Emulator”