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.

Non-Invasive Smart Electricity Meter

There are a lot of ways to measure energy usage in the home, but most of them involve handling mains voltage. Not only that, but sometimes they require handling mains voltage before it gets through a breaker panel or fuse box, meaning that if you make a mistake there are a lot of bad things that can happen. [Yonas] has been working on this problem, and has come up with a non-invasive, safer way to monitor electricity consumption without having to work directly on live wires.

Please note that you should still not be working on mains voltage without proper training, but if you have the required know-how then the installation should be pretty straightforward. The project is based on the Spark Core, and uses clamp-on current sensors to measure energy use. The sensors wrap around the mains cable, meaning you don’t have to disconnect anything to hook them up. The backend runs on a LAMP server which could be a Raspberry Pi if you have one. [Yonas] runs it on a hosted server as a matter of preference.

All of the source code for this is available, and assuming you can get your hands on the current sensors this could be a great way to get started monitoring your energy usage in the house. Be sure to check out the video below for a demonstration of the operation of this device. Of course, if you have a gas line you’ll need this energy monitoring setup too.

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Portable 120V to 240V Converter; or How to Fast Charge at Your In-Law’s House

[Nick Sayer] falls into the “would rather build it than buy it” category. This particular project is a clone of a fast electric vehicle charger. There are commercially available versions sold under the Quick 220 brand name. The idea is that for fast charging, some electric vehicles call for a 240V outlet and Americans without electric cars often don’t have one. If they do it’s for an appliance like a stove or clothes dryer and probably not found in the garage.

The device uses two hot and one ground to supply the 240V output which is, in some business where there is three phase power this will be closer to 208V but should still work. Obviously you shouldn’t be doing this unless you know exactly how it works, and we applaud [Nick] for airing these hazards while at the same time supplying the knowledge behind the concerns.

Two inputs for the beefy converter are supplied from outlets not just on separate circuits, but on two circuits whose hot lines are 180 degrees out of phase. That means identifying where there are two plugs, not protected by GFCI outlets or breakers, which are on two separate hot lines of split phase power. To protect the user, [Nick] designed in a set of relays which kill the circuit when one of the two supplies is unplugged. A system that didn’t have these protections would have mains voltage on the prongs of the disconnected plug.

We’ve seen very few car charging hacks. If you know of one, or have been working on your own, let us know!

Mains Power Detector For A Thing For Internet

inductor The Internet of Things is fast approaching, and although no one can tell us what that actually is, we do know it has something to do with being able to control appliances and lights or something. Being able to control something is nice, but being able to tell if a mains-connected appliance is on or not is just as valuable. [Shane] has a really simple circuit he’s been working on to do just that: tell if something connected to mains is on or not, and relay that information over a wireless link.

There are two basic parts of [Shane]’s circuit – an RLC circuit that detects current flowing through a wire, This circuit is then fed into an instrumentation amplifier constructed from three op-amps. The output of this goes through a diode and straight to the ADC of a microcontroller, ready for transmission to whatever radio setup your local thingnet will have.

It’s an extremely simple circuit and something that could probably be made with less than a dollar’s worth of parts you could find in a component drawer. [Shane] has a great demo of this circuit connected to a microcontroller, you can check that out below.

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Guitar EQ levels trigger the stage lights


Even if your band hasn’t made it big yet it’s still a lot of fun to put on a great show. This hack will help you add lighting effects to performances without having to shell out for a lighting technician. [Phil] put together a hack that lets you trigger the lights by setting a volume threshold with a pedal switch.

After reading about the hack that adds an EQ display for a pedal board he got the idea to convert the concept as control hardware instead of just for feedback. Just like the visualization project he uses an MSGEQ7 chip which takes care of the audio analysis. He’s using this for electric guitar so he only monitors three or four of the outputs using an Arduino. He built the hardware into a foot pedal by mounting a momentary push button on the lid of the enclosure. Stepping on the button causes the Arduino to save the the current audio level. Whenever it reaches that threshold again it will switch on a mains relay to drive an outlet. In this case a strobe light turns on when he starts to rock out, which explains the bizarre image above. You can get a better feel for the theatrics by watching the clip after the break.

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Hacking grandfather clock accuracy while it’s still ticking


[Keith] got his hands on a few grandfather clocks. Apparently the price tag is greatly reduced if you are able to get them second-hand. The mechanical timepieces require weekly winding, which is a good thing since you’ll also need to correct the time at least that often. But this drift got [Keith] thinking about improving the accuracy of these clocks. He figured out a high-tech way to adjust the timepiece while it’s ticking.

The first thing he needed was a source of super-accurate time. He could have used a temperature compensated RTC chip, but instead went the more traditional route of using the frequency of mains power as a reference. The next part of the puzzle is to figure out how to both monitor the grandfather clock and make small tweaks to its pendulum.

The answer is magnets. By adding a magnet to the bottom of the pendulum, and adjusting the proximity of a metal plate positioned below it, he can speed up or slow down the ticking. The addition of a hall effect sensor lets the Arduino measure the rate of each swing and calculate the accuracy compared to the high voltage frequency reference.

Mains rated solid state relay test box


We like our nice, safe, 5V prototyping projects where the only thing that might get fried is a chip. But there are times when you want to switch appliances for one reason or another and then you’re going to want a mains rated relay. [Viktor] got tired of having exposed high voltage on the bench during the prototyping stage of these projects so he recently built a solid state relay test box.

The only thing he bought for the project was the SSR itself. To act as an enclosure he used the brick from an old laptop power supply. This is perfect for a couple of reasons. First off, it’s designed to contain high voltage if there is ever a short or other problem. Second, it’s already setup for incoming and outgoing power. He just needed to remove the guts and mount the relay. Notice that it comes with a clear plastic shield that physically separates the high voltage side from the low voltage control end. This, along with the cable routing, keeps the dangerous stuff on one side to ensure you won’t get an arc to the low voltage portion of the project.