Compost heap temperature logger helps keep things hot

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HackHut user [lackawanna] is looking to start his own compost pile, but as many urban composters discover, things can get quite smelly if you don’t manage it properly. The process of composting is broken up into two phases, aerobic and anaerobic decomposition. The former is the first stage to occur and produces plenty of heat, but should be scentless. The latter gives off less heat and is more of a stink due to putrefaction. Carefully monitoring the temperature of the pile and restarting the aerobic phase when necessary helps to keep the process “healthy” and scent-free.

[lackawanna] built a simple temperature monitor that he plans on using to track the status of his compost pile once he gets started. It uses an ATmega328 as the brains of the operation and an old metal can transistor as his temperature sensor. Using relative measurements of the compost pile taken in 10 minute intervals, he can determine when the aerobic phase is underway, as well as when things begin turning anaerobic. At that point, the sensor alerts him that the pile needs to be turned.

The build is pretty simple, but leaves plenty of room for expansion. It should be relatively easy to add a more friendly notification interface as well as install multiple sensors to the pile for obtaining aggregate temperature data.

PCB parts salvaging made easy

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Take a moment to think about how many old or damaged computer motherboards you have tossed away over the years. Sure we try to repurpose everything we can, but reclaiming electronic components from complex devices can be overly time consuming if you don’t have the proper means of doing so.

Ideally, if we were to try removing components from a motherboard, an old stove or an unused toaster oven would be great. If you didn’t have either item at your disposal, you could always attack the board with a soldering iron and some braid – but who has the time for that?

[Giorgos Lazaridis] over at PCBHeaven put together a quick video demonstrating his favorite technique for salvaging components after a motherboard has outlived its usefulness. Using a 2000W heat gun, a few hand tools, and couple of metal pans, he had the entire board stripped bare in about 30 minutes time. He talks about some of the best parts he has discovered while salvaging and points out a few hard-to-find items that can be easily obtained by tearing down a motherboard.

Sure his process might not be as easy as inverting a PCB in an oven, but his method is cheap, portable, and takes up very little space.

Keep reading to see [Giorgos’] video demonstration and don’t forget to check out some of the other cool stuff he has done in the past, such as his temperature-controlled soldering station, this acrylic bender, or this bench top function generator.

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Light-sensing circuit for power saving applications

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Instructables user [MacDynamo] was thinking about home security systems and wondered how much electricity is being wasted while such systems are powered on, but not activated. He pondered it awhile, then designed a circuit that could be used to turn a security system on or off depending on the time of day, but without using any sort of clock.

His system relies on a 555 timer configured as a Schmitt trigger, with a photoresistor wired to the reset pin. When the ambient light levels drop far enough, the resistance on the reset pin increases, and the 555 timer breaks out of its reset loop. This causes the circuit to power on whatever is connected to it. When the sun rises, the resistance on the reset pin drops and the 555 timer continually resets until it gets dark again. He notes that this behavior can be easily reversed if you were to put the photoresistor on the trigger pin rather than the reset pin.

We like the idea, though we are a bit wary about using this for any sort of real security system. An errant insect or debris could cause the system to be turned on, and we’d feel pretty foolish if someone disabled our alarm with a flashlight. That said, this sort of circuit still has plenty of practical, power-saving applications outside the realm of home security.

NXT machine sorts LEGO blocks automatically

Smart people don’t put their toys away, they build machines to do it for them. Case and point: this NXT project which can sort LEGO pieces. Just dump a bucket of random blocks in a hopper on one end of the machine. One slice at a time, these plastic pieces will be lifted onto a conveyor system made up of several different belts, which allows for separation of the parts. One block at a time, each piece enters a specially lighted chamber where they are visually identified by the NXT brick. Once it identifies the block, a carousel of plastic containers rotates to place the correct home for the block below the output shoot seen above.

So do we now have a completed LEGO circle of life? Not quite. You can build structures automatically using a 3D LEGO printer and this sorter will have no problem organizing the parts for that purpose. But we still need a LEGO machine that can tear assembled bricks apart.

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MIDI drum interface helps you step up your game

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[Dan] likes Rock Band, but playing it makes him feel as useful as a one-legged man in an ass-kicking a drumming contest. He says that even using his friend’s ION kit leaves him searching out excuses as to why he’s not as good as he should be on the drums.

Eventually, he decided that he would settle things once and for all. The final excuse he came up with was that it is too difficult to press the drum pedal rapidly without getting tired, as the Rock Band gear does not properly simulate real drum equipment. Bass pedals on professional kits are weighted and balanced to allow the drummer to exert the least amount of work for the most return, resulting in a less tiring experience.

To give him a leg up while playing the game, he decided to rig a trigger to his Yamaha MIDI bass pedal, which is properly weighted. He consulted the Rock Band forums, and after looking at a couple of different circuit diagrams, he designed his own. He etched a PCB, mounted his SMD components, and was well on his way to becoming a drum legend.

He says that the pedal interface works quite well, and despite a couple of tiny soldering setbacks, he has yet to see any errant hits register in-game.

Be sure to check out the video below of his drum trigger undergoing some tests.

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Converting from clutter closet to dreamy datacenter

[DocDawning] had a nice home network up and running, but the messy pit housing the hardware made him avoid that part of the house. In an effort to cut down on noise, and clean up the clutter, he built himself a very nice data center inside a small closet.

One of the biggest changes in the setup provides adequate cooling. He cut a vent hole into a wall shared between the closet and a hallway. This was just the right size for a few large cooling fans which suck air into the enclosed space. But cool-air intake must be accompanied by hot-air outflow so he added an exhaust vent in the ceiling. This also received a trio of big fans, and as you can see above, the integrated LEDs act as a light source for the server farm.

The final part of the plan involved machine-specific brackets mounted to the walls of the enclosure. These racks were built out of 1×1 white wood. They hold the hardware in place leaving plenty of room to run cables. The new setup even opened up enough wall space to mount power and networking hardware. Now everything has its place, and [DocDawning] can finally close the door on his noisy servers.

Mayor is a hacker and wants to use DIY parking meters

The Mayor of Silverton, Oregon is a hacker and wants to use roll-your-own hardware in the town’s parking meters. It’s not that he thinks he can do a better job than companies selling modern meters (although there have been notable problems with those), but he wants to retain the sentiment of the 1940’s era parking meters that are being replaced. Those meters are known as penny parking meters, because you can get 12 minutes of time for just one penny.

Many municipalities have gone digital with parking payment systems due to costs associated with servicing mechanical meters and collecting coins from each one of them. This hack aims to keep the look of the vintage meters, but replace the mechanical readout with a digital screen. The meter would still offer a reasonable parking deal; five minutes for free. Cost for replacing the internals is estimated at $150 per meter… which seems just a bit high if they are looking at a 250 unit run. The main problem that we see with the idea is that the original parking meter bodies don’t have a slot which can accept quarters.

[Thanks Rick]