555

174 Articles

RFID Entry Uses Homemade Electronic Strike

September 9, 2010 by 22 Comments

[Fileark] built an RFID entry system that uses a pretty ingenious alternative to an electronic strike plate. An electronic strike is a rather expensive hinged plate that mounts in the door frame and catches the door latch. But this system opens a set of double doors. The door without the handle is fixed in place and has a normal strike plate. But it also has a deadbolt mounted in line with that plate. When the deadbolt is extended it is flush with the strike plate, pushing the latch from the door knob back and freeing the door to swing open. This is a bit hard to put into words so watch the video after the break to clear things up.

The system uses a cheap RFID package that provides a single signal line. This line connects to an old VCR motor which turns the deadbolt. Timing is provided by a 555 chip, and the deadbolt movement is limited by a couple of switches mounted along with the motor.

Now that the unlocking mechanism has been built it would be simple to use other authentication methods for unlocking the door, like a wristwatch-based proximity system.

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Electronic Vuvuzela

July 13, 2010 by 27 Comments

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

Want to annoy fellow fans but  don’t have the lung power to do the job? [Hunter’s] electronic vuvuzela is just the thing you need. The plastic noisemakers were so prevalent at the world cup this year that some folks came up with audio filters to remove the sound. The electronic rendition is much smaller, using a 555 timer to mimic the instrument on a small speaker. [Hunter’s] build has buttons for five different notes which can be altered with some potentiometer. There’s no schematic but then again for something that’s annoying you don’t want to make it too easy to replicate.

Update: Hunter added the schematic to his site which spell doom for those who enjoy peace and quiet.

Beginner Concepts: 555 Push Button Toggle

February 2, 2010 by 29 Comments

PIC, AVR, and Arduino are ubiquitous in projects these days and a lot of the time it’s easy to over-complicate things with their use. In this case, [Tod] wanted to use a momentary tactile switch to turn something on and off. Instead of going with a microcontroller he built the circuit around a 555 timer. What he really needed in this case is a flip-flop but lacking a chip for that he went with the 555 because it has one built-in. Three resistors and a capacitor later he’s in business, adding another resistor and a transistor to deal with the load switching. We’ve embedded video of the circuit controlling an LED after the break. This IC ends up in a lot of projects so dig through your parts bin and give this circuit a try.

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Simplest Most Useless Machine

December 30, 2009 by 42 Comments

[youtube=http://www.youtube.com/watch?v=Z86V_ICUCD4]

[Brett] posted about his most useless machine build. His project gives us a chance to massacre the language in the title because it uses the lowest parts count we’ve see with these machines. The logic is controlled by our friend, the 555 timer. Add to that just one servo motor, two switches, three resistors, two caps, a diode, and a battery pack and you’re in business. The hardest part to find locally is the servo but check at a hobby/RC store. If you don’t have to put in a parts order this can be your next impulse project.