Proximity switch for your mains devices

[Ivan's] friend built a proximity sensor to switch his LED bench lighting off every time he walked away. The idea is pretty neat, so [Ivan] decided to implement it for mains devices by making this proximity switched outlet box.

A Sharp GP2D12 infrared distance sensor is the key to the system. It has an emitter and receiver that combine to give distance feedback base on how much of the light is reflected back to the detector. This is presented as a voltage curve which is monitored by an ATtiny85 (running the Arduino bootloader). It is small enough to fit inside the outlet box along with a tiny transformer and linear regulator to power to logic circuitry. The mains are switched with a relay using an NPN transistor to protect the chip’s I/O pins.

Check out the video after the break to see this in action. It should be a snap to add a count-down timer that gives you a bit more freedom to move around the workshop. With that in place this is a fantastic alternative to some other auto-shutoff techniques for your bench outlets.

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Christmas prep starts early: MIDI control for strings of lights

If you’re planning to outdo yourself with this year’s Christmas decorations now’s the time to start planning. After all, what else have you got going on since the dreadful heat is making outdoor activities a sweat-soaked misery? Take some inspiration from [Tim] who just finished prototyping a wireless MIDI controller for his strings of Christmas lights. You can just see the four spools in the distance which are lighting up as he tickles the ivories.

The wireless link is provided by a WiFi access point which uses its USB port to control the external hardware. This is a USB Bit Whacker board which in turn drives a relay board that was designed to switch mains voltages. The high voltage parts of the rig are housed in a plastic food storage container which hosts two pair of outlets to drive four channels in total. [Tim] is happy with the outcome, which he shows off in the video after the break, and hopes to expand to a total of sixteen channels for this year’s festivities.

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Under-bench timed outlets won’t let you leave the iron on

When we used to use firesticks (the pen style plug-in soldering irons) it was always a worry that we might leave them on. But now we use a base unit which has an indicator light to serve as a reminder. Still, [FoxxTexx] isn’t taking any chances and instead built this timer-based outlet which kills the power automatically.

The parts are all pretty common. The timer itself is the same form factor as a light switch and is commonly used for heat lamps or hot tub jets. It feeds the outlet next to it by way of the indicator switches to the right. We like the use of the switches but since mains voltage is still running through them we would suggest using a three-gang box and mounting them on the cover plate so that all the wiring is contained. If done this way you could just have the electrical box siting on your bench, but it is a nice touch to have it mounted this way.

We’ve long been proponents of a timer system. Back when we put together our Hacker’s Soldering Station we just used a plug-in timer unit.

Home automation with RC wall plugs and Raspberry Pi

[Jake] took some cheap hardware and figured out a way to use it as a huge home automation network. He’s chose a Raspberry Pi board to connect the radio controlled power outlets to his network. He wrote about his project in two parts, the first is hacking the RC outlet controller and the second is using the Raspberry Pi to manipulate it.

These RC outlets are a pass-through for appliances that connect to mains (lamps, consumer electronics, christmas trees, etc). Often the protocol used by the cheap-as-dirt remote is difficult to work with, but [Jake] really hit it out of the part on this one. In addition to simulating button presses for up to fifteen devices on the remote, he replaced the DIP switch package. This lets him change the encoding, essentially allowing the one device to control up to 32 sets of outlets. Theoretically this lets him command 480 devices from the Raspberry Pi. Since that board is a web server it’s just a matter of coding an interface.

Some of the inspiration for this hack came from the whistle-controlled appliance hack.

Controlling the power with bluetooth

[Mike] dropped us a tip to show off a system he has built to control some power sockets based on his proximity.  Initially the project started as a parallel port controlled box to switch the mains power.  Then he got the idea of turning this into a little more interactive of an automation tool. He is utilizing the bluetooth from his cell phone as a locator. When the box senses that he’s in the room, the power is on. When he leaves the area, the power is off.  You can see his ruby code on his web site if you wanted to give it a try or offer improvements.

UPS with dead batteries reborn as a whole-house power backup

[Woodporterhouse] must deal with regular power black outs in his area. He recently converted a rack-mount uninterruptible power supply to feed a portion of his mains wiring. This one is not to be missed, since he did such a great job on the project, and  an equally remarkable job of documenting it. It’s one of the best examples we’ve seen of how to use Imgur as a project log.

The UPS still needs to have a case, but it doesn’t need room for batteries as he’s going to use a series of high-end sealed lead-acid batteries. So he cut down the enclosure to about half of the original size. That’s it mounted just above the new batteries. For this to work you need some type of transfer switch which can automatically patch between incoming line voltage, and the battery backup. He already had one of these switches in place for use with a generator, that’s it in the upper left. The entire system powers a sub-panel responsible for his essential circuits — the electronics in the home and a few lighting circuits (we’d assume this includes utilities like the refrigerator).

One really great feature that the reused UPS brings to the project is a monitoring card with a NIC. This way he can check the server to see if the UPS is being used, and how much of the 14 battery life remains.

[Thanks Ross via Reddit]

Using mains wiring as an antenna

Make sure to brush up on your safety protocol if you undertake this project. The penalty for messing up when using live wiring as a radio receiver antenna is rather severe. But after reading about it in some old books [Miroslav] decided to give this technique a try.

We love the old-school chalk board he used to map out his test circuit. With safety in mind, he uses two high voltage capacitors in series. If these should somehow fail, there is also a fuse which would blow, disconnecting the apparatus from mains. But just to be sure, he isolated the circuit using a two coils. These step down the voltage, but would also burn out if hit with a voltage spike.

You can see the results he gets using the setup as an AM radio receiver in the video after the break. He tested against a meter long antenna and found that his setup far outperforms it. Actually, he found that a six foot extension cord which is not plugged into the wall will also outperform the 1m antenna. Something to keep in mind the next time the ball game isn’t coming in as clear as you would like.

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