RFID Door Lock – The Right Way

November 17, 2009 by Mike Szczys 40 Comments

[youtube=http://www.youtube.com/watch?v=XT7E_GEIPVg]

[Pcmofo] has shared a well-built, well-explained example of how to implement an RFID key system for a door. We call this the right way because it is well thought out and functional. In the past we’ve seen doors that unlock via a secret knock, keypads, and RFID, but they are all non-permanent solutions capable being transplanted from one door to another. Rather than building a mechanism to turn the door handle, this implementation uses an electric strike mounted in the framing of the door to allow access. These are used for security doors in buildings and are built to keep your door secure.

The hack in this case is the electronics. Using an AVR ATmega168 running the Arduino boot-loader, [pcmofo] has prototyped a two-part design. An RFID reader is mounted outside the door with data wires running to the inside where the microcontroller resides. A hard-coded RFID card is used as a “master” to train any number of tags for entry. The master puts the device in training mode and the next tag to be read is added to the list of tags authorized to open the door.

We like messy wires and quickly thrown together devices but this is built to last and will look great once mounted in an appropriate enclosure.

Rotating Radar Visualization

November 16, 2009 by Jakob Griffith 32 Comments

[flickr video=http://www.flickr.com/photos/peplop/4106571163/]

We ask, who wouldn’t want a rotating motion and distance tracking radar? Sure in today’s day and age anyone could purchase a wide-angle sonar or IR solution that achieves the same goal, but [LuckyLarry] took it old school and made his own rotating radar. He used an Arduino, servo, and ultrasonic sensor as a base to gather data, and the open source programming language Processing to draw the data on the screen. He says it’s a little inaccurate currently, but will try out some other sensors in the future.

Radar Detector Tester

November 15, 2009 by Caleb Kraft 38 Comments

[Blacklight99] made this cool tool. It is a tester for those radar detectors that people keep in their cars. Though this seems like it would rarely be a tool we would need, it’s an interesting project. Some speed guns that the police use have a “stealth” mode that makes them invisible to some detectors. This tool can tell you if your detector is vulnerable to this. While this really is just a complicated flashing LED, he notes that it could be taken further to be made into a detector that is programmable and not vulnerable to any of the stealth modes.

R/C Lawnmower

November 14, 2009 by Caleb Kraft 56 Comments

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[Johndavid400] built this incredible looking R/C lawnmower. After spending some time repairing broken R/C cars, he wanted to move on to something a little more useful and powerful. He decided to build a mower. He’s using a transceiver set from ebay, with an Arduino interpreting the signal and outputting to his custom motor board. In the video after the break, you can see that the mower looks responsive and quick. He does note, however, that he had some glitches early in the process that left him with a runaway mower. We covered a very similar mower ages ago that used a wheelchair as the base.

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Duino Tag

November 13, 2009 by Jakob Griffith 31 Comments

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During our daily rounds we stumbled upon Duino Tag. Sure it’s not as awesome as a coil gun but it really sparked our imagination. First the base: an Arduino is wired up with IR LEDs and placed inside of a plastic pistol. A second Arduino with an IR receiver is scanning for the first Arduinos signal. A ‘shot’ of IR light is ‘fired’ and detected, you get a ‘kill’.

The base is nothing amazing, but it really gives us some ideas and we would like to see it expanded upon. [J44] has already put in a piezo and other LEDs to simulate muzzle flash and other effects. But we like to go further. Start off with multiple pistols and players. Include GPS to track players current position, and wireless to update each player of another player. A small wrist watch display could act much like a UAV. Add some expansions like IR ‘grenades’ and you’ve got a full-out war! What would you like to see?

Too Much Time, Not Enough Pressure

November 12, 2009 by Mike Szczys 14 Comments

[Audin] got a hold of a pressure gauge and decided to turn it into a clock. We were under the impression that these types of gauges were filled with oil but he didn’t detail cleaning it up for his purposes. Once he gained access to the guts he replaced them with a stepper motor. The motor connects to an Arduino with the help of a Darlington array for handling the large load. [Audin’s] plans include using a real time clock (on order) and moving to an AVR ATmega8 microprocessor once the prototyping is finished. In the mean time, he has posted the code used in his current prototype.

Stay with us past the page break for some video of this in action. He’s got the needle dialed in for very precise movement and has coded a “jitter” effect as well. We’re not sure this would be the most convenient clock, but we’d love to affix it to our kitchen stove for a gnarly looking timer. [Audin] acquired the gauge at his local Habitat for Humanity ReStore, a place we’ve used many times to source reclaimed and unused items of all kinds for our projects.

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Battery Capacity Tester

November 11, 2009 by Mike Szczys 16 Comments

battery-capacity-tester

[Moris_zen] built a device to accurately measure the capacity of batteries. He needed to have an accurate measurement for the batteries he uses in a RC airplane. Knowing the discharge time allows him to fly the friendly skies while avoiding crashes from lost communications.

He based the tester around the Arduino platform. Instead of using a pre-built Arduino board he referenced the open source schematics and built the device from components to fit his needs. His solution automatically detects the battery type (Lithium-Ion, Nickel Metal Hydride, etc) based on voltage when the battery is added to the circuit. It then uses a 2.2 Ohm resistor and ADC measurements to take the battery through a discharge cycle. A character display shows status information with the ability to track discharge information using a computer to graph the data.

Apart from flashing an LED this was his first Arduino project. It’s a great use of the platform and much more automatic than other solutions we’ve covered.