Arduino Parking Lot Attendant

October 15, 2012 by Mike Szczys 25 Comments

Here’s an automatic parking gate for toy cars. There’s no need to press a button, the electronics detect the presence of a vehicle on either side of the gate, raising it after verifying that the lot is not already full. It’s the same idea as counting how many people enter a room in order to switch the lights but the hardware is just a bit different.

The system is controlled by a pair of sensors in the paper which serves as the parking lot. There are three sheets of heavy stock, the top and bottom both have aluminum foil on them, with the center layer as a separator. There are holes cut in the separator where the hash marks are seen above. By adding a little pressure to the car when you drive it up to the gate this completes a circuit instructing the Arduino that there’s a vehicle in position.

You can see a demonstration, as well as the guts of the build, in two videos after the break.

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Janus: The Gatekeeper

September 29, 2012 by Jeremy Cook 10 Comments

[Piet] wrote in to tell us about his hack that allows for his front gate to be opened without a key. Unlike this hack that we featured in August, you don’t need a subway pass, just a good memory. As explained in his article (and the video after the break) if the proper sequence of doorbell rings is input, the gate unlocks itself.

For hardware a [mehduino] is used to take the doorbell input and decide whether or not the “secret knock” has been achieved. The door can be unlocked remotely via a button on the processor. Reprogramming the code is achieved by simply holding the program button while the code is entered on the “remote ringer” button.

Be sure to check out the video after the break to see this lock in action. The housing application may not be exactly what you expect. Also of interest, is that in true hacker fashion, the bare processor is hanging by a hook on his wall! Continue reading “Janus: The Gatekeeper” →

Automatic Speaker Control Via TV

August 15, 2012 by Mike Szczys 5 Comments

[Jon] wanted his speakers to come on and off along with his TV. The speaker heats up if left on so he didn’t want to do that. But killing the power also resets the volume level (this is an old set of PC speakers and the remote is wired, not IR) so using one of those switched power strips was out as well. He thought a bit about trying to use the power LED on the TV to build his own circuit when it dawned on him. It’s possible to monitor the USB port on the TV and use it to switch on the speakers.

The circuit above uses a couple of opto-isolators to protect both the television and the speakers. The 5V line from the USB port on the back of the TV is monitored by an XNOR gate (which helps to filter out some of the toggling at power-on). When that gate latches it activates a 555 timer which in turn fires up the speakers. Presumable this happens when power is cut as well, but we’ll let you work through the circuit logic yourself.

Automated Entry For A Garden Gate

September 14, 2010 by Mike Szczys 14 Comments

[Dan McGrath] tipped us off about a solution for a problem that most people don’t have. He built a web-based entry system for his garden gate. This isn’t quite as original as that chain and sprocket dorm room system, but it does use a keypad for entry. [Dan’s] already got a web server and home automation box that is always running. He coded a webpage that presents a virtual keypad for code entry. If the right code is input the system unlocks the electronic strike on the other side of this gate. Since the interface is a web page you can load if from any web browser (an iPhone is used for demonstration purposes after the break). But if you don’t have internet access you’re in trouble; there’s no physical keypad. But we guess you could always just jump the fence. Continue reading “Automated Entry For A Garden Gate” →

AVR Guardian Filters Out Dogs

July 19, 2010 by Mike Szczys 29 Comments

Cats and dogs can get along quite nicely when they are raised up together. The problem with this type of arrangement tends to be keeping dogs out of the cat box and away from the cat food. [Ryan Meuth] tried out a simple electronic barrier to keep the dog away. It uses an IR transmitter and receiver to shine a beam of invisible light across the doorway to his cat room. In the demo after the break you’ll see that he took steps to make sure the cats don’t set off the alarm. The beam of light is set high enough that their bodies don’t get in the way, and the firmware measures the amount of time the beam was broken in order to avoid false positives caused by the cats’ tails. If the dog does try to get into the room it will break the beam and set off a high-pitched alarm sound.

It’s interesting that the dog doesn’t like the sound but the cat’s don’t seem to be scared of it. Also, we’ve got a less-than-ferocious feline that would love to chew on the cord that connects the two modules. Still, it’s a solution that works for [Ryan] and could be incorporated into an automatic feeder to keep the dog away from feedings while you’re out of the house.

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