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164 Articles

A Field Guide To The North American Communications Tower

April 5, 2016 by 98 Comments

The need for clear and reliable communication has driven technology forward for centuries. The longer communication’s reach, the smaller the world becomes. When it comes to cell phones, seamless network coverage and low power draw are the ideals that continually spawn R&D and the eventual deployment of new equipment.

Almost all of us carry a cell phone these days. It takes a lot of infrastructure to support them, whether or not we use them as phones. The most recognizable part of that infrastructure is the communications tower. But what do you know about them?

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Color TV Broadcasts Are ESP8266’s Newest Trick

March 1, 2016 by 39 Comments

The ESP8266 is well known as an incredibly small and cheap WiFi module. But the silicon behind that functionality is very powerful, far beyond its intended purpose. I’ve been hacking different uses for the board and my most recent adventure involves generating color video from the chip. This generated video may be wired to your TV, or you can broadcast it over the air!

I’ve been tinkering with NTSC, the North American video standard that has fairly recently been superseded by digital standards like ATSC. Originally I explored pumping out NTSC with AVRs, which lead to an entire let’s learn, let’s code series. But for a while, this was on the back-burner, until I decided to see how fast I could run the ESP8266’s I2S bus (a glorified shift register) and the answer was 80 MHz. This is much faster than I expected. Faster than the 1.41 MHz used for audio (its intended purpose), 2.35 MHz used for controlling WS2812B LEDs or 4 MHz used to hopefully operate a reprap. It occasionally glitches at 80 MHz, however, it still works surprisingly well!

The coolest part of using the chip’s I2S bus is the versatile DMA engine connected to it. Data blocks can be chained together to seamlessly shift the data out, and interrupts can be generated upon a block’s completion to fill it in with new data. This allows the creation of a software defined bitstream in an interrupt.

Why NTSC? If I lived in Europe, it would have been PAL. The question you’re probably thinking is: “Why a dead standard?” And there’s really three reasons.

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ESP8266 Transmits Television On Channel 3

January 31, 2016 by 57 Comments

We’ve seen a lot of ESP8266 projects in the past, but this one most definitely qualifies as a hack. [Cnlohr] noticed that the ESP8266, when overclocked, could operate the I2S port at around 80MHz and still not lose DMA data. He worked out how to create bit patterns that generate RF around 60MHz. Why is that interesting? Analog TVs can receive signals around that frequency on channel 3.

As you can see in the video below, the output is monochrome only and is a little snowy. It also will lose frames on some WiFi events, but this is all forgivable when you consider this very inexpensive module isn’t meant to do video output at all.

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Fixing Broken Monitors By Shining A Flashlight

January 22, 2016 by 67 Comments

[dyril] over on the EEVblog has a broken LED TV. It’s a fairly standard Samsung TV from 2012 that unfortunately had a little bit of corrosion on the flexible circuit boards thanks to excessive humidity. One day, [dyril] turned on his TV and found about one-third of the screen was glitchy. After [dyril] took the TV apart, an extremely strange fix was found: shining a light on the corroded flexible circuit board fixed the TV.

The fix, obviously, was to solder a USB light to a power rail on the TV and hot glue the light so it shines on the offending circuit. Solving a problem is one thing, though, understanding why you’ve solved the problem is another thing entirely. [dyril] has no idea why this fix works, and it’s doubtful anyone can give him a complete explanation.

The TV is fixed, and although you can’t argue with results, there is a burning question: how on Earth does shining a light on a broken circuit board fix a TV? Speculation on the EEVblog thread seems to have settled on something similar to the photonic reset of the Raspberry Pi 2. In the Raspberry Pi 2, a small chip scale package (CSP) used in the power supply section would fail when exposed to light. This reset the Pi, and turned out to be a very educational introduction to photons and energy levels for thousands of people with a Pi.

The best guess from the EEVblog is that a chip on the offending board handles a differential signal going to the flex circuit. This chip is sensitive to light, and shutting it down with photons allows the other half of the differential signal to take over. It’s a hand-wavy explanation, but then again this is a very, very weird problem.

You can check out [dyril]’s video demonstration of the problem and solution below. Thanks [Rasz] for sending this one in.

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Toy Television’s Dreams Come True

October 21, 2015 by 12 Comments

A couple of years ago, [Alec]’s boss brought him a souvenir from Mexico City—a small mid-century console television made of scrap wood and cardboard. It’s probably meant to be a picture frame, but [Alec] was determined to give it a better life.

As it turns out, the screen of [Alec]’s old Samsung I9000 was a perfect fit for the cabinet with room to spare. It was on its way to becoming a real (YouTube) TV once [Alec] could find a way to control it remotely. A giant new-old stock remote that’s almost bigger than the TV was just the thing. There’s enough room inside the remote for a non-LE Bluefruit module, which is what the I9000 will accept as input without complaint.

Trouble is, Bluefruit doesn’t support matrix keypads, so [Alec] used a bare ATMega328 running on the internal clock. Since the Bluefruit board provides voltage regulation, the remote was able to keep its native 9V power. [Alec] is happy with the results, though he plans to refine his button choices and maybe make a new overlay for the remote. Stay tuned for a tiny TV tour.

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Remote Tester

A Simple Circuit For Testing Infrared Remote Controls

June 15, 2015 by 25 Comments

Every now and then a remote control acts up. Maybe you are trying to change the channel on your television and it’s just not working. A quick way to determine if the remote control is still working is by using a cell phone camera to try to see if the IR LED is still lighting up. That can work sometimes but not always. [Rui] had this problem and he decided to build his own circuit to make it easier to tell if a remote control was having problems.

The circuit uses a Vishay V34836 infrared receiver to pick up the invisible signals that are sent from a remote control. A Microchip 12F683 processes the data and has two main output modes. If the remote control is receiving data continuously, then a green LED lights up to indicate that the remote is functioning properly. If some data is received but not in a continuous stream, then a yellow LED lights up instead. This indicates that the batteries on the remote need to be replaced.

The circuit also includes a red LED as a power indicator as well as RS232 output of the actual received data. The PCB was cut using a milling machine. It’s glued to the top of a dual AAA battery holder, which provides plenty of current to run the circuit.

Spectrum Analyzer On The Cheap

March 12, 2015 by 27 Comments

Provided you have an NTSC-compatible TV you can build yourself a really inexpensive spectrum analyzer. From there you just need one trivial piece of hardware to complete this build. [Bruce Land] has come up with a spectrum analyzer that shouldn’t cost any more than $5, if that’s what’s been keeping you from adding this tool to your workbench!

The spectrum analyzer is based on a PIC32 microcontroller which was previously proven in his Oscilloscope project. [Bruce] has managed to squeeze quite a bit out of this robust chip; the spectrum analyzer has 450 kHz bandwidth and runs a 256 Hz TV display and can output over 30 updates per second. The microcontroller runs the Fast Fourier Transform (FFT) to do calculations, with great results.

[Bruce] notes that the project was based on TV framework from another project, and that the FFT was added on top of that. Be sure to check out the source code on the project site if you’ve been on the hunt for an inexpensive spectrum analyzer, and if you need something with more processing power but only slightly more money, check out the FFT that runs on the Raspberry Pi’s GPU.