Compost Heap Temperature Logger Helps Keep Things Hot

April 8, 2011 by Mike Nathan 12 Comments

compost_temp_logger

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.

Toothpaste Diode

March 16, 2011 by Kevin Dady 39 Comments

While reading the back of a tube a toothpaste [Underling] noticed that one of the ingredients was hydrated silica, gears turned, sparks flew and he wondered if he could possibly make a transistor out of the stuff. After thinking about it he decided that making a diode out of toothpaste would be easier and still prove the idea.

The quick n dirty explanation of this is he smeared some toothpaste on a bit of chrome and set it on fire with a propane torch. When set on fire the result is silica and sodium, heat causes the sodium to bond with the silica and since sodium is negatively charged this forms an n-type semiconductor or half of the diode. Chrome is used for the second half of the diode, for a few reasons, he had some lying around, its positivity charged, and the toothpaste contains a little bit of lye which oxidizes the chrome and burns off, bonding the silica to the metal.

What is left is a thin layer of chrome doped silicon under a layer of sodium doped silicon, which in spots where everything is perfect, acts like a diode, blocking current in one direction but not the other.

Cooking Up Piezo Crystals At Home

March 15, 2011 by Mike Nathan 56 Comments

piezo_crystal

[Collin] loves piezos – and why not?

According to him, they are about as close to magic as you can find in the world. We can’t really disagree on that one – there’s something oddly enchanting about piezoelectric materials.

Most commercially used piezoelectric devices that you find today are constructed out of man-made ceramic materials such as Lead zirconate titanate, and can be found in grill starters, gas-powered water heaters, etc. While they are common, it’s not exactly easy to synthesize these sorts of ceramic materials at home.

You can however, create piezoelectric crystals in your kitchen, using just a few simple ingredients. In his video, [Collin] shows us how to create Rochelle Salt, one of the first known materials found to exhibit piezoelectricity. The recipe calls for three ingredients, cream of tartar, sodium carbonate (soda ash), and water – that’s it. The procedure is quite simple, requiring you to heat a solution of water and cream of tartar, adding the soda ash a little at a time once it reaches the proper temperature. The solution is filtered after it turns clear and then left to sit overnight while the crystals form.

Take a look at the video embedded below to see how his Rochelle Crystals turned out, and be sure to try this out with your kids if they are interested in electronics. Making crystals that generate electricity when tapped is far cooler than making rock candy any day, trust us on this.

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Simple PCB Etchant Made From Chemicals You Can Put In Your Mouth

March 3, 2011 by Mike Nathan 68 Comments

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[Stephen] often finds the need to make his own PCBs at home, and when he got the urge to do some etching recently, he realized that he was fresh out of “Ferret Chloride and Bureaucratic Acid*.” Undeterred by his empty chemical cabinet, he poked around in his kitchen mixing together anything and everything that might have the ability to strip copper from a PCB.

Now, we don’t necessarily recommend this course of action, but it seems that he finally hit upon a winner. He discovered a formula that can be made at home from simple and safe household ingredients which does the job quite nicely. A fair warning however, standard ferric chloride disposal procedures need to be followed when using this solution.

If you want to know what he concocted in his kitchen as well as the chemistry behind it, you will have to visit his site, we won’t ruin it for you. You can however, see the solution at work in the video we have posted below.

*His joke, not ours

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Arduino-Fart-O-Meter

February 16, 2011 by Kevin Dady 24 Comments

[robomaniac] shows us some serious application of modern technology with his recent Instructable, (the) Arduino-Fart-O-Meter. The wireless device uses a “perfboard Arduino” to read a remote wired methane sensor, and send data over a nRF2401A radio transceiver.

“The data” is picked up by another Arduino / transceiver combo, which then drives a servo motor connected to the pointer. The meter itself consists of 6 ranges from “Fresh Air” to “Liquid” so there is no doubt in your standing.

The wireless and remote sensor setup makes this an easy device to include into your loved ones chairs while having the meter far enough away (just in case you have to make a run for it). If you want some more accuracy check out the Fart intensity detector we posted about, which adds in temperature and sound to the equation, or how about a chair that twitters your toots?

Join us after the break for a quick video, its a real gas.

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Accidental LED Fabrication

December 28, 2010 by Mike Szczys 36 Comments

[Grenadier] had a piece of silicon carbide sitting around that he planned to use when making a primitive diode called a Cat’sWhisker Diode. While probing he noticed that one of the crystals threw off a bit of light. He popped it off and used JB Weld to attach it to a brass plate. The peculiar thing is that it generates light when power is run through it both forward and reverse biased. So what’s going on here? According to an informed discussion on the phenomenon there’s actually a pair of diodes in series but with their polarity reversed.