DIY Seven Segment Displays

[Esai] wanted to build an electronic clock from scratch. A noble quest, but ordinary seven-segment displays are just that – incredibly ordinary. Instead of a few displays that can be bought from the usual retailers for a dollar a piece, [Esai] made his own four digit, seven-segment display on some perfboard.

Before soldering 58 SMD LEDs to a small rectangle of perfboard, [Esai] traced out each segment with a marker. Two LEDs make up each segment, and they’re all connected to a breadboard-friendly pin header with 30 gauge wire.

Each segment is connected as a single column in the LED matrix, and each digit is a row. It’s a simple design, but there aren’t any resistors on this board. Hopefully [Esai] will be using a proper LED driver with this display; you really don’t want LEDs to burn out twice a day at 1:11.

11,000 Volt Jacob’s Ladder Sounds Like a Lightsaber

In the high-voltage world, a Jacob’s ladder is truly a sight to behold. They are often associated with mad scientist labs, due to both the awesome visual display and the sound that they make. A Jacob’s ladder is typically very simple. You need a high voltage electricity source and two bare wires. The wires are placed next to each other, almost in parallel. They form a slight “V” shape and are placed vertically. The system acts essentially as a short-circuit. The voltage is high enough to break through the air at the point where the wires are nearest to each other. The air rises as it heats up, moving the current path along with it. The result is the arc slowly raising upwards, extending in length. The sound also lowers in frequency as the arc gets longer, and once [Gristc] tuned his system just right the sound reminds us of the Holy Trilogy.

We’ve seen these made in the past with other types of transformers that typically put out around 15,000 Volts at 30mA. In this case, [Gristc] supersized the design using a much beefier transformer that puts out 11,000 Volts at 300mA. He runs the output from the transformer through eight microwave oven capacitors as a ballast. He says that without this, the system will immediately trip the circuit breakers in his house.

In the demo video below, you can see just how large the arc is. It appears to get about 10 inches long before breaking with a sound different from any Jacob’s ladders we’ve seen in the past as well. Continue reading “11,000 Volt Jacob’s Ladder Sounds Like a Lightsaber”

Using Cheap Displays With The Raspberry Pi

The Raspberry Pi B+ has a native VGA connection. Sure, it’s hidden away in binary blobs and device trees, and you need to wire up the GPIO pins just right, but it’s possible to connect a VGA monitor to a Raspi B+ natively. For the brave, smart, or foolish, this means you can also drive raw DPI displays. [Robert] had a few of these dirt cheap displays sitting around and decided to give the entire thing a go. It worked, and he’s written down how to do it.

One of the chip architects for the Raspberry Pi, [Gert van Loo], was exceedingly clever when designing the Pi. There’s a parallel interface in the chip that, when combined with a few dozen resistors, can drive a VGA display in addition to the HDMI display. Screens with a Display Parallel Interface are actually pretty similar to what the VGA spec calls for. The problem is, hardly any of this is documented for the Raspberry Pi, and finding it means trawling through forums.

[Robert]’s example circuit uses a 5″ display from Adafruit, a 40-pin breakout, and a bunch of prototyping wires. Setup requires grabbing a cut down version of the device tree used for the Raspi VGA breakout board, setting the output format, rgb order, and aspect ratio of the display, and wiring everything up.

What’s interesting here is that [Robert] reproduced this project from scratch, and found that any display with a 40-pin DPI connector will work with the Raspi, provided you have a datasheet. That’s pretty cool; these displays can be cheap, and since we don’t yet have a proper DSI display for the Pi, this will have to do for now.

Video below of [Robert]’s inspiration for this build, [Ladyada].

Continue reading “Using Cheap Displays With The Raspberry Pi”

Running Doom On The Intel Edison

A few months ago, the Intel Edison launched with the promise of putting a complete x86 system on a board the size of an SD card. This inevitably led to comparisons of other, ARM-based single board computers and the fact that the Edison doesn’t have a video output, Ethernet, or GPIO pins on a 0.100″ grid. Ethernet and easy breakout is another matter entirely but [Lutz] did manage to give the Edison a proper display, allowing him to run Doom at about the same speed as a 486 did back in the day.

The hardware used for the build is an Edison, an Arduino breakout board, Adafruit display, speaker, and PS4 controller. By far the hardest part of this build was writing a display driver for the Edison. The starting point for this was Adafruit’s guide for the display, but the pin mapping of the Edison proved troublesome. Ideally, the display should be sent 16 bits at a time, but only eight bits are exposed on the breakout board. Not that it mattered; the Edison doesn’t have 16 pins in a single 32-bit memory register anyway. The solution of writing eight bits at a time to the display means Doom runs at about 15 frames per second. Not great, but more than enough to be playable.

For sound, [Lutz] used PWM running at 100kHz. It works, and with a tiny speaker it’s good enough. Control is through Bluetooth with a PS4 controller, and the setup worked as it should. The end result is more of a proof of concept, but it’s fairly easy to see how the Edison can be used as a complete system with video, sound, and wireless networking. It’s not great, but if you want high performance, you probably won’t be picking a board the size of an SD card.

Video demo below.

Continue reading “Running Doom On The Intel Edison”

The Original Seven (Eight?) Segment Display

The seven-segment LED display is ubiquitous. But how old do you think the fundamental idea behind it is? You nixie tube fans will be thinking of the vacuum-tube era, but a reader sent us this patent filed in 1908 where [Frank W. Wood] builds a numeric display with plain-vanilla light bulbs, slots cut in wood, and lots of wires.

The OCR on the patent is poorly done — you’re going to want to download the PDF and read it locally. But as it states in the patent, “Referring again to Fig. 1, the novel arrangement of the lamp compartments will be readily understood.”

Technically it’s not a seven-segment display at all. [F.W. Wood] designed these really nice-looking “4”s with the diagonal heads, and so he needed eight segments per digit. But the basic idea shines through, if you pardon the pun.

The other figures demonstrate the machine that’s used to send the signals to light up the lights. It’s a rotating drum with the right contacts on the bottom side to make connections and turn on the right lights at the other end. Low tech, but it’s what was available at the time.

We’re stoked that we’re not responsible for wiring this thing up, and we’re a bit awed by how old the spirit behind one of our most ubiquitous technologies is.

Thanks to [mario59] for the nostalgic tip!

Hackaday Links: The Last One Of 2014

The guy behind the Microslice, a tiny Arduino-controlled laser cutter, has a new Kickstarter out. It’s called the Multibox PC, and it’s exactly what you need if you want to turn a Raspi, Banana Pi, HummingBoard, or Odroid U3 into an all-in-one desktop. 14″ 1366 x 768 LCD, and speakers turns dev boards into a respectable little Linux box.

If you’re learning to design schematics and lay out PCBs, you should really, really think about using KiCAD. It’s the future. However, Eagle is still popular and has many more tutorials. Here’s another. [Mushfiq] put together a series of tutorials for creating a library, designing a schematic, and doing the layout.

Another kickstarter wristwatch. But wait, this thing has a circular display. That’s really cool. It’s a 1.4″ 220×220 pixel, 262k color display. No, the display doesn’t use a polar coordinate system.

[Jari] wrote a digital logic simulator, Atanua, started selling licenses, and figured out it wasn’t worth developing on his own anymore. As promised, Atanua is now open source. If you want to look at the finances behind Atanua, here you go.

In 1970, you didn’t have a lot of options when it came to memory. One of the best options was Intel’s 1405 shift register – 512 bits of storage. Yes, shift registers as memory. [Ken Shirriff] got his hands on a memory board from a Datapoint 2200 terminal. Each of the display boards had 32 of these shift registers. Here’s what they look like on the inside

There’s a lot of talk about North Korean hackers, and a quick review of the yearly WordPress stats for Hackaday puts a tear in our eye. This year, there were fifty-four views from the Democratic People’s Republic of Korea. That’s just great. It’s awesome to see the hacker ethos make it to far-flung lands and through highly restricted firewalls. There’s still a long road ahead of us, though, and we’ll redouble our efforts on bringing the hacker mindset to Tuvalu and Saint Helena in the year 2015.

Home Automation Setup Keeps You Informed

[johannes] wrote in to tell us about his latest project, a home automation setup he named Botman. While he calls it a home automation system, controlling lights and home appliances (which it does wirelessly on 433MHz) is just a small part of its functionality. The front panel of Botman includes a servo which points to laser-etched icons of the current weather. It also has a display which shows indoor and outdoor weather conditions along with the status of public transportation around [johannes]’s house.

Botman is built around an Arduino with an Ethernet shield. The Arduino has very little memory, so [johannes] used the Google Apps engine as a buffer between his Arduino and the JSON APIs of his data sources. This significantly reduces the amount of data the Arduino has to keep in memory and parse.

[johannes] also wrote an Android app that communicates with Botman. The app has buttons for controlling lights in his house and duplicates all the information shown on the front panel. [johannes] also built some logging features into Botman. The temperature readings and other information are uploaded from the Arduino to a Google Docs spreadsheet where he can view and graph them from anywhere. Check out the video after the break to see Botman in action.

Continue reading “Home Automation Setup Keeps You Informed”