Garden sensors measure soil moisture and greenhouse temperature

May 14, 2012 By Leave a Comment

[Andy] is getting his garden up and running. This year it’s been pretty cold so he decided to get small plastic domed tunnel which acts as a mini greenhouse. To help monitor that environment he built this sensor array which displays temperature and soil moisture readings.

Temperature is quite simple. He’s using a TMP36 sensor which is held a few inches above the soil. The moisture sensor is of his own design. It uses two building screws embedded in foam. These are pushed into the soil and a resistance reading indicates moisture level. By driving voltage on one screw, and measuring voltage on the other he gets some useful data. It’s not a standardized value, but observation over time will let him know how the scale relates to dry or wet soil.

During the build process he found that he needed a pull-down resistor on the probe used to take the moisture measurement. He also uses an I/O pin to drive the other screw. This gives him a way to shut off the juice when not taking a reading. We just hope he’s either got a current limiting resistor, or is using a transistor to drive it high.

Filed Under: arduino hacks Tagged With: , , , , ,

Graphic equalizer display flashes LED sign to the beat

May 14, 2012 By Leave a Comment

Careful planning and a steady hand let [Leo Rampen] fit everything he needed to build a graphic equalizer display on his LED wall sign. There’s a lot of components that needed to fit on this board, and he decided not use to an etched board for the build.

The idea for the project started off as just an LED sign. After spelling out “Sweat Box” using LED rope lights, he needed a way to switch them on and off. But why stop there? He also decided to use an MSGEQ7 chip in the build since the sign adorns their party-room and adding music-based flashing lights seemed like a good idea.

He laid out the equalizer chip, ATmega328 (running the Arduino bootloader) and a series of N-channel MOSFETS for switching the LEDS out in Eagle. With design in hand he grabbed a medium-sized piece of strip board and used a drill to cut the traces where necessary. In the end he has a very flashy sign as shown in the clip after the break.

[Read more…]

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Arduino compatible home automation for smart phone or voice control

May 14, 2012 By Leave a Comment

[Joseph] wrote in to share this home automation system he’s working on as a college project. He calls it the Room Engine and the house-side of the hardware is built on top of the circuit you see here. This is the most basic part of the REBoard, which is meant to connect to a computer uses RS232 or USB, and in turn use a set of relays to switch mains voltage devices.

You can follow the bread crumb on his webpage to get a broader video of the system. The interface is designed to use two parts. One is a voice recognition system that is supported by the computer. The other is an iOS interface that includes login credentials and a button-based control system. The video after the break shows off the smart phone portion of the controller. We think he’s done a good job of integrating a few appliances without the need for commercial products such as X10 modules.

If you’re just interested in switching a few things without cord’s reach of each other this can get it done, and offers scheduling functionality. It would also be pretty easy to set this up with a WiFi module and do away with the PC.

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Filed Under: home hacks Tagged With: , , , ,

Helicopter light painting continues to snuff out physics lesson on your brain

May 14, 2012 By Leave a Comment

Cool picture, huh? Wait until you see the video footage of this LED-adorned RC helicopter flying on a dark night. But this isn’t an art project. Analyzing the long-exposure photography turns out to be a great way of clearing up some of the physics of flight which otherwise are not at all intuitive. The helicopter used here has different colored lights on the nose and tail, as well as lights on the rotors.

Depending on how the aircraft is moving, different 3D spirography is captured by the camera. When you zoom in on part of the flight path it becomes clear that there are wider arcs on one side of the fuselage than there are on the other. This has to do with the forward progress of the aircraft and the rotation of the blades. The phenomenon is well known by helicopter enthusiasts, and accounted for in the design. But what we didn’t realize is that it actually translates to a theoretical speed limit for the aircraft. Our childhood love of Airwolf — the TV helicopter that could outrun jets — has been deflated.

You should remember the helicopter physics videos featured here last month. This is the latest offering and we’re still wanting more!

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Filed Under: featured, led hacks, toy hacks Tagged With: , ,

Recycle lithium cells by building custom flashlights

May 14, 2012 By Leave a Comment

This isn’t a brightest flashlight in the world type of hack (but it does manage to push about 1000 lumens). [Stephen Webb] is finding a use for leftover parts by building his own simple LED flashlights. As you can see, he uses PVC parts available at any hardware or home store. These are a good choice; they’re cheap, light weight, resilient, designed to be water tight, they easily thread together and have connectors that reduce the diameter of the fittings.

The electronics use standard size cylindrical Lithium cells. These are found in many types of Laptop and Power Tool batteries. Often when one of those battery packs bites the dust it’s an issue of one or more bad cells. [Stephen] desolders the cells, and reuses the good ones in this project.

We didn’t see any mention of a recharging technique. Does anyone have any advice on how to top these cells off if they’re not in their original power pack form?

Filed Under: green hacks, led hacks Tagged With: , , ,

Designing a self-replicating milling machine

May 14, 2012 By Leave a Comment

For his senior design project at Swarthmore College, [Julian] decided to build a metalworking equivalent to the RepRap. [Julian]’s final project is a self-replicating milling machine, and hopefully giving some serious metalworking power to all the makers with CNC routers and RepRaps out there.

At first glance, [Julian]’s mill doesn’t look like something you would find in a machine shop. The machine is built around a tetrahedral machine tool frame, giving the machine an amazing amount of stiffness with the added bonus of a degree of self-alignment. The spindle and motor are off-the-shelf units, but the entire bed assembly is made by [Julian] himself.

Right now, [Julian] still considers his project a very early prototype; there’s still a bit of chatter issues he’s working out, and the cost of the finished machine – about $1200, not including many hours of fine tuning – means it isn’t as competitive as other options. Still, [Julian] made a mill from scratch, and that’s nothing to scoff at.

Filed Under: tool hacks Tagged With: ,
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