Traffic signal controller pulls data over WiFi

[Travis Brown] just published a post about the traffic light controller he built. His number one goal was to make the device wireless (except for AC power) and he achieved this by using a WiFi shield for his Arduino. But there is also a separate board that provides a way for the chip to switch the AC lights.

He works for a web hosting company, and the boss wanted a fun way to display the status of the servers among other things. He chose to use the WiServer library which controls the CoperHead WiFi Shield and gives him the ability to serve simple web pages from the Arduino. When power is applied the sketch automatically connects to the AP and starts polling the company’s API for status data. If you’re not within eyesight of the traffic lights you can log into the web server and check that way.

We think [Travis] did a great job of explaining his code, and we applaud him for making proper use of the watchdog timer (something we don’t see in very many projects). This joins the pile of traffic-light display devices we’ve seen around here. We still don’t know where people are getting their hands on the things.

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Monitoring software builds with a traffic light

[JD] at isotope11 was looking for a way to get instant feedback whenever a developer broke a piece of software they were working on. After finding a 48 inch tall traffic light, he knew what he had to do. Now, the entire development team knows the status of their code from a traffic light hanging in the corner.

isotope11 runs a continuous integration server to do the quality assurance on their software projects. It’s a lot more flexible than the ‘compile and pray’ setup we’re used to, but then again C isn’t very well suited to test-driven development. When one of [JD]’s developers breaks a piece of code, the CI server will send a warning to an Arduino where all the electronic magic happens.

To light the traffic light, [JD] used a few relays to drive the 120 volt bulbs in the traffic light. The traffic light is very easy to read – red means something is broken, green means everything is alright, and yellow means a test suite is being run.

Check out the video of [JD]’s TDD visualization after the break.

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Stop light converted to control office foot traffic


When [Paul Rea] started work with his current employer, he was intrigued by a traffic light that sat unused near the entrance of the “Engineering Loft” where he was stationed. He promised himself that he would get it working one day, but several years passed before he had the chance to take a closer look at it.

He took the light home with him over Thanksgiving weekend last year, and started to dig around inside to see how things were wired up. It turns out the light was a pretty simple contraption, though he discovered it ran on mains voltage, something [Paul] didn’t really want to fiddle with. He swapped out the traffic light’s bulbs for some low-voltage models, which he could easily power with a 12v wall wart.

[Paul] then added an Arduino and PIR sensor to the light fixture in order to detect when someone was leaving the Engineering Loft, warning those who are on their way in. He says that people don’t really pay attention to the light very much, though he is pretty happy with the results.

Continue reading to see a short video of the traffic light in action.

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SIM card carrying traffic lights

Apparently some of the traffic lights in Johannesburg, South Africa have SIM cards in them to help maintain the network without a physical connection. Now that’s some and not all, but apparently thieves have learned that the SIMs can be used in cell phones to make anonymous and unlimited calls. Officials are convinced that the thieves have inside information because they only crack open the lights that DO contain a card.

We’re white hats here at Hackaday and certainly don’t want to give out information that aids criminals. But since this is already a huge problem we have an idea of how thieves might be identifying which lights to rob. Sure, they probably do have inside information, but wouldn’t it be fairly simple to track down which lights use cellular communication by using a home made spectrum analyzer? We guess it would depend on how often the lights send out communications bursts. Does anyone have insight on this? Leave you thoughts in the comments.

[Thanks Bob]

Fabricating a music-controlled stoplight

[Andrew] built himself a stoplight that flashes along with the music. Unlike the traffic signal we checked in on a year ago, this one’s not a reused municipal fixture. [Andrew] imported a 3D model into Sketchup, printed out the results, and traced them onto Bristol board to make his templates. He cut out the parts, used a brake for the bending, then a combination of spot and MIG welding to complete the housing. Off to his school’s spray booth for priming, baking, and painting for a perfect finish.

The internals are what you’d expect. Each light source is made up of a cluster of LEDs controlled by an Arduino. Music synchronization is handled by a Processing script that [Andrew] wrote, which you can see in action after the break.

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Arduino traffic light

[Rockwell] sent us an update on his traffic light hacking. Dedicated readers will remember seeing this legally attained traffic signal controlled through a parallel port from back in 2005. The new update swaps the old port for USB and adds several autonomous functions which are demonstrated in the clip after the break. The update includes a nice UI and some notifications for things like email, IMs, Reddit posts, etc.

He’s given control of the hardware over to an Arduino. Instead of building the board into the project he’s included just the parts he needs; an AVR running the Arduino bootloader, a crystal and filtering caps, and an Arduino serial to USB module for connectivity. The AC load switching is handled by three relays. The relays he links to are 12VCD rated coils. We think this should have pointed to 5VDC coils as that’s the voltage that the logic circuit are running at. Be careful with switching these AC loads, this traffic light isn’t a toy.

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