Controlling Mains Power Rube Goldberg Style

[g3gg0] has some nice radio equipment including an AOR AR-5000 receiver and a HiQ SDR. They are so nice that it appears they lack an on/off switch. [g3gg0] grew tired of unplugging the things, and decided to nerdify his desk with a switch that would turn his setup on and off for him. He decided to accomplish this task by emulating the Scroll, Number and Caps Lock LEDs on his keyboard via a Digispark board. He uses the LEDs to issue commands to the Digispark allowing him to control a 5V relay, which sits between it and the AC.

Starting off with some USB keyboard emulation code on the Digispark, he tweaked it so he could use the Scroll Lock LED as sort of a Chip Select. Once this is pressed, he can use the Caps Lock and the Number Lock LED to issue commands to the Digispark.

It’s programmed to only stay on for a total of 5 hours in case he forgets to turn it off. Let us know what you think about this interesting approach.

DDR-ing a Simon Game with a Raspberry Pi

Since 1998 we’ve been privileged to partake in an arcade game known as Dance Dance Revolution, but before that, way back in the 70’s, was the Simon game. It’s essentially a memory game that asks the player to remember a series of lights and sounds. [Uberdam] decided to get the best of both worlds and mixed the two together creating this giant foot controlled Simon game. (English translation.)

The wood platform that serves as the base of the project was fitted with four capacitive sensors, each one representing a “color” on the Simon game. When a player stomps on a color, a capacitive sensor sends a signal to a relay which in turn notifies the Raspberry Pi brain of the input. The Pi also takes care of showing the player the sequence of colored squares that must be stepped on, and keeps track of a player’s progress on a projector.

This is a pretty good way of showing how a small, tiny computer like the Raspberry Pi can have applications in niche environments while also being a pretty fun game. We all remember Simon as being frustrating, and we can only imagine how jumping around on a wooden box would make it even more exciting. Now, who can build a robot that can beat this version of Simon?

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Hackaday Prize Entry: Controlling Relays Over WiFi

It’s been less than a year since the ESP8266 WiFi Module was released. This is a chip whose original data sheets were only available in Chinese, could only be controlled through AT commands, and was (originally) only sold through Seeed Studio and other various Chinese retailers. It had one thing going for it: it was five dollars. For the price of a crappy sub, you can blink an LED from the Internet. Needless to say, the ESP8266 is now very popular.

There are a lot of ESP8266 projects in The Hackaday Prize this year, and [David]’s project is making great use of the relatively meager pinout of this module. He’s built an 8-channel relay controller with a WiFi interface to control industrial equipment. It’s a great project, but just of many ESP projects in the prize this year.

The ESP doesn’t have a huge number of pins, but there are enough for some serious work with the right hardware. He’s using the ESP-12 module to get the most pins, and using an SPI port expander to drive an octet of relays. It’s a simple board, but everything you need to control a bunch of relays over WiFi is right there: LEDs, reset buttons, and RS232 level conversion.

You can check out a pair of very satisfying videos of relays clicking below.


The 2015 Hackaday Prize is sponsored by:

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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.


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!

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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.

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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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