Etch PCBs With Ferric Chloride And A Sponge

July 13, 2009 by Zach Banks 29 Comments

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Etching a printed circuit board generally takes a bit of time and uses a lot of etchant. [TechShopJim] posted a method that uses a sponge to reduce the amount of etchant used while speeding up the entire process. First, a resist is applied using either a sharpie or the toner transfer method. Using gloves to handle everything, he soaked a sponge in ferric chloride and continually wiped a copper-clad board until all the exposed copper was removed. This technique moves the etchant around more, keeping “fresh” etchant closer to the copper. If you can’t procure ferric chloride, you can also use our method that uses 2 household chemicals: hydrogen peroxide and hydrochloric acid.

Arduino Nano Updated

July 13, 2009 by Eliot 22 Comments

The official Arduino Nano design has been updated to version 3.0. Like other new Arduino designs, it’s using the ATmega328 instead of the ATmega168. It’s also a slightly more reasonable $35. The small board is designed to be plugged directly into a breadboard and accessed via mini USB cable. This new design is also two layers instead of four making it easier to produce and modify. The new Nanos will ship at the end of the month.

Photo Interrupters Explained

July 12, 2009 by Caleb Kraft 20 Comments

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[Eric] sent in this very informative writup on how to use Photo interrupters. These things can be used for many things, he lists pellet dispensing and limit switches. He found one in his junk box and realized he knew very little about it. After some exploring and research, he’s here to educate the rest of us. There’s a good breakdown of the circuit itself which is pretty simple as well as a test circuit and some sample code.

Hacking An IButton

July 9, 2009 by Zach Banks 36 Comments

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Maxim’s iButtons, which are small ICs in button-sized disks, are starting to show up in more and more places. They have a range of uses, from temperature loggers to identification, and all use the 1-wire protocol to communicate. Over a furrtek, they hacked an iButton used for buying things from vending machines and created an infinite money cheat. They built a small rig based on the ATmega8 to read and write data to the chip. The data was encrypted, so it wasn’t feasible to put an arbitrary amount on the card. Instead, they used a similar technique to the Boston subway hack and restored a previous state to the iButton after something was bought. They also created a hand-held device to backup and restore the contents of a button for portable hacking.

[Thanks furrtek]

AVR Boost Converter

July 7, 2009 by Zach Banks 19 Comments

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Over at SpriteMods, [sprite_tm] realized that a microcontroller could be used as a boost converter to power itself. A boost converter steps up voltage from a battery by switching the output of a coil. First, it is tied to ground so a magnetic field can build up in the coil. It is then released as a higher voltage than the input. Normally dedicated chips do this at an incredibly high frequency, but the PWM signal from an AVR works well enough. This can be used in low-power situations where space is an issue.

[via EMSL]

Battery Desulfator

July 5, 2009 by Eliot 30 Comments

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Hack a Day favorite [Mikey Sklar] is back with a new project. Mini-D is a battery desulfator. If a 12V lead-acid battery sits with a voltage below 12.3V, sulfur crystals will begin to form on the lead plates. This crystal growth increases the internal resistance and eventually makes the battery unusable. A battery desulfator sends high frequency pulses through the battery to create a resonance that will break up the crystals. On a 60lb automotive battery, it will take approximately three weeks to completely desulfate. You can find schematics plus a dozen lines of code for the ATmega169 on his site. Embedded below is a video where he explains the device and other techniques like load testing.

Continue reading “Battery Desulfator” →

Capacitive Discharge Spot Welder Update

July 5, 2009 by Eliot 22 Comments

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It seems one of our commenters took great umbrage with [PodeCoet] not documenting his capacitive discharge cutting properly. [PodeCoet] had been waiting till he got the full spot welder working before publishing, but he’s expedited the work after all our whining. Check out his full writeup of the device in its current state. It uses a 1Farad audio cap for storage. A dsPIC monitors all of the voltage sources and regulates charging. A nice touch is the tactile switch on the electrode.