Gates To FPGAs: TTL Electrical Properties

On the path to exploring complex logic, let’s discuss the electrical properties that digital logic signals are comprised of. While there are many types of digital signals, here we are talking about the more common voltage based single-ended signals and not the dual-conductor based differential signals.

Simulated "Real Life"
Single-ended Logic Signal

I think of most logic as being in one of two major divisions as far as the technology used for today’s logic: Bipolar and CMOS. Bipolar is characterized by use of (non-insulated gate) transistors and most often associated with Transistor Transistor Logic (TTL) based logic levels. As CMOS technology came of age and got faster and became able to drive higher currents it began to augment or offer an alternative to bipolar logic families. This is especially true as power supply voltages dropped and the need for low power increased. We will talk more about CMOS in the next installment.

TTL was a result of a natural progression from the earlier Resistor Transistor Logic (RTL) and Diode Transistor Logic (DTL) technologies and the standards used by early TTL became the standard for a multitude of logic families to follow.

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Talk Of The Town: Hacker Channel Tomorrow

Get in touch with Hackers everywhere. Take part in the Collabatorium tomorrow, live!

request-to-join-hacker-channelThings get started on Wednesday, July 1st at 6:30pm PDT (UTC-7). Hundreds of hackers will be on hand discussing what they’re building, all the stuff happening in the hacker-sphere these days, and joining forces for that next great hack!

All are invited to take part. Head on over the Hackaday Prize Hacker Channel right now and click on the left sidebar link that says “Request to join this project”.

We highly recommend adding a custom avatar (if you haven’t already) so that others in the Collabatorium will be able to put a picture to your personality. The interface is ready for chat, links, images, code and much more so bring your questions and share your knowledge.

Now that you’ve clicked for an invite, while away the hours until it begins by heading over to VOTE in this week’s Astronaut or Not. And soon after you run through your 50 votes we’re sure you’ll also figure out you don’t have to wait for us to get the conversation started in the Hacker Channel ;-)

Maker Faire Kansas City: Entrepreneurial Spirit Taking Shape

One of the great things about an event like the Kansas City Maker Faire is that there are so many reasons that makers sign up to show their things. Some makers come to teach a skill, and others to sell their handmade creations. Those with an entrepreneurial streak looking to launch a product might rent a booth to get a lot of eyes on their idea. That’s just what [Ted Brull] of Creation Hardware was after this weekend–exposure for Kevo, his small-scale vacuum former.

kevo-mt-dewKevo is a simple and affordable solution for makers of all stripes. It can be used to make molds, blister packaging for items, or even electronics enclosures. [Ted]’s Kickstarter campaign for Kevo has already been successfully funded, but there’s still plenty of time to get a Kevo kit for yourself. The basic reward includes the vacuum-forming chamber and two sizes of adapters that cover most vacuums. It also ships with an aluminium frame to hold polystyrene sheets during the heating and molding processes, and starter pack of pre-cut pieces in black, white, and clear plastic.

Creation Hardware had many vacuum-formed molds on display and were constantly making more from 3D-printed objects, toys, and other things. Our favorite mold was a 20oz bottle of Mountain Dew, which shows how far the small sheets of plastic can stretch.

Beest Of An RC Toy

Sometimes hackers and makers hack and make stuff just because they can. Why spend hours in a CAD program designing a gazillion gears, brackets and struts? Why cut them all out on a homemade CNC? Why use a PIC and perf board to control everything? Because we can. Well, because [Est] can, rather. He put together this RC controlled beast of a toy with multiple legs and crushing claws.

It’s made out of 6 mm acrylic and threaded rod. The legs are controlled by two DC motors, while the mouth uses two geared steppers. The beast talks to the controller via a pair of 433 MHz transceivers using a protocol similar to how an IR remote talks to a television. A handful of LEDs lights up the clear acrylic, making it look extra scary.

This design is, of course, based on the Strandbeest concept from [Theo Jansen]. It’s a great robotics project because your project doesn’t suffer under its own weight. It’s more like a tracked machine. In fact, we saw a huge rideable version made of metal at BAMF this year. That’s one you just can’t miss!

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Vibrating Distance Torch Illuminates The Dark Without Light

If you’ve ever had to move around in a dark room before, you know how frustrating it can be. This is especially true if you are in an unfamiliar place. [Brian] has attempted to help solve this problem by building a vibrating distance sensor that is intuitive to use.

The main circuit is rather simple. An Arduino is hooked up to both an ultrasonic distance sensor and a vibrating motor. The distance sensor uses sound to determine the distance of an object by calculating how long it takes for an emitted sound to return to the sensor. The sensor uses sounds that are above the range of human hearing, so no one in the vicinity will hear it. The Arduino then vibrates a motor quickly if the object is very close, or slowly if it is far away. The whole circuit is powered by a 9V battery.

The real trick to this project is that the entire thing is housed inside of an old flashlight. [Brian] used OpenSCAD to design a custom plastic mount. This mount replaces the flashlight lens and allows the ultrasonic sensor to be secured to the front of the flashlight. The flashlight housing makes the device very intuitive to use. You simply point the flashlight in front of you and press the button. Instead of shining a bright light, the flashlight vibrates to let you know if the way ahead is clear. This way the user can more easily navigate around in the dark without the risk of being seen or waking up people in the area.

This reminds us of project Tacit, which used two of these ultrasonic sensors mounted on a fingerless glove.

Hackaday Prize Entry: Circular Knitting Machines

Deep in the recesses of a few enterprising hackerspaces, you’ll find old electronic knitting machines modified for use with modern computers. They’re cool, and you can knit colorful designs, but all of these machines are ultimately based on old equipment, and you’ll have a hard time building one for yourself.

For their entry to the Hackaday Prize, [Mar] and [Varvara] is building a knitting machine from scratch. Not only is it a 3D printed knitting machine anyone can build given enough time and plastic, but this machine is a circular knitting machine, something no commercial offering has yet managed.

We saw [Mar] and [Varvara]’s Circular Knitic last January, but this project has quite the pedigree. They originally started on their quest for a modern knitting machine by giving a new brain to old Brother machines. This was an incredible advancement compared to earlier Brother knitting machine hacks; before, everyone was emulating a floppy drive on a computer to push data to the machine. The original Knitic build did away with the old electronics completely, replacing it with a homebrew Arduino shield.

While the Circular Knitic isn’t completely 3D printed, you can make one in just about any reasonably equipped shop. It’s a great example of a project that’s complex and can be replicated by just about anyone, and a perfect example of a project for The Hackaday Prize.

Check out the video of the Circular Knitic below.

The 2015 Hackaday Prize is sponsored by:

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semi auto bed leveling

Semi-Automatic Bed Leveling Your 3D Printer

Two of the most important prerequisites for successful 3D printing is making sure the bed is level and correctly setting the Z=0 height. Getting both of these right almost guarantees great adhesion since the first print layer is not only at the right distance from the build platform but also at a consistent distance for the entire bottom surface of the part.

Manual bed leveling is tedious, requiring the user to move the print nozzle to different points around the build platform, adjust some screws and make sure the nozzle is a piece-of-paper’s thickness higher than the platform. If you want to get complicated, there is an automatic option that probes the build platform and makes height corrections in the software. The probes come in several flavors, two common methods being a deployed mechanical switch (usually mounted to a servo) or force sensors under the build platform that sense when the nozzle touches the build platform. This method also requires some fancy firmware finesse to get working correctly.

[Jonas] posted a video showing the semi-automatic bed leveling capability of his printer. The build platform is held a bit high by springs that surround each of the 3 screws that support the bed assembly. The nozzle is moved directly over one of the 3 screws and then moved down until it noticeably presses on the build platform, compressing the support spring. A thumb wheel is then tightened at that location, locking the bed in place. The same process is performed for the other 2 support points. The result is a perfectly level build surface. Check the video out after the break to see just how quick this procedure is!

We’ve seen a somewhat similar concept that uses a clever gimbal and lock system under the bed.

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