[Andrea] built this LED chaser using one logic chip. It illuminates all but one of the six LEDs, with the dim bit moving back and forth along the row in a chase sequence. This is something like an inverse Larson Scanner without the fading tail. But doing it with a logic chip instead of a microcontroller is a fun challenge.

Which brings us to the point of this feature. [Andrea] didn’t really post an explanation of how the circuit works. Usually missing details mean that we archive the tip and move on to the next one, but we think this provides a fun activity. Can you figure out how the circuit works? We already know that it’s using a CD4017 decade counter/divider chip. This gets its clock signal from a 555 timer circuit. [Andrea's] schematic is a bit hard to read, but grab a copy, blow it up a bit (or use your browser zoom) and study the CD4017 datasheet (PDF) if you need to.

Want proof that it does actually work? It’s embedded after the break.

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We’re really not supposed to start a feature like this; but this hack is awesome. It’s a game of Snake implemented by an FPGA dev board. It uses a 16×16 LED matrix as the display and an SNES controller for input. So far it sounds like a very normal version of the game. But as you start to hear how it works in the presentation after the break you fall in love with what’s going on here.

First of all, it’s not written in VHDL — the predominant programming language for FPGAs. Instead, [Darrell] used the schematic-only approach to build the logic. Okay, that’s starting to get more interesting. As he continues to explain the circuit we get to see how the control input works (pretty simple since the SNES controller uses a parallel-to-serial shift register) and how the display is multiplexed. But the actual game logic is where things really take off. Each pixel in the display has its own individual logic circuit. Basically every cell is its own processor which reacts both to what is passed into it, as well as to a random seed. That seed system is called the ‘bucket brigade’ and passes a chance to spawn a piece of food from one cell to the next. All of this together makes for one simple game that is eloquently executed. Read the rest of this entry »

[74hc595] just finished his entry in the 7400 logic contest. It’s a drum machine built entirely from 7400-series logic chips. He hasn’t quite reached full completion of the project yet. The hardware works just fine, and he’s built a foam core face plate with many more controls than you see here but much of the circuit is still on a breadboard at this point and only two of the channels have been complete thus far.

Jump to the video clip after the break to get the details of how the system works and to hear it in action. This demonstration is one of the best we’ve seen for a synthesizer project as he actually talks about what each control does, and how that is accomplished with the hardware. We’re not going to go into detail about the circuitry he’s designed. As we said before, it uses 7400 logic but also sources a 555 timer to keep the beat. The page linked above has a PDF of the schematic available and you could really lose a lot of time studying how he did this. We might even try to build it in a simulator to see what we can learn.

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[Caleb] is hard at work on a driving game based on 7400 series logic chips. This will be his entry in the Open 7400 Logic Competition, and it really outlines why this contest is especially tricky.

The concept behind the game is quite simple. You’re the driver of a car (the red dot at the bottom of the display square seen above) and need to navigate the curves in the road as you drive along. It’s the same game as we saw played on receipt paper back in June. [Caleb's] using and LED matrix as the display, and we’re confident that if we grabbed our favorite microcontroller we could have this up and running on an 8×8 bi-color display in an afternoon. But doing it without the crutch of a programmable chip really brings out the clever engineer inside of you.

The circuit seen above is a Logisim proof-of-concept that [Caleb] went on to test on the breadboard. He thought he had everything figured out until he realized that his Data Flip-Flops were very occasionally not powering up in the same state as he predicted. Don’t worry, he found a solution to the problem. But we can’t wait to see what other hurdles he encounters as he pushes on toward completing the project.

Here’s another chance to ply your hacking skills for cash and prizes. Dangerous Prototypes has just announced the Open 7400 Logic Competition. First prize is $100 and a bunch of hacking goodies. But even better is that since it was announced, more sponsors have stepped up to increase the kitty, and the number of entries that will get prizes.

The parameters for entry are wide open. You can design anything you want, with emphasis on originality. Make sure you take plenty of pictures and document the project along the way. Their judging will take into consideration the amount of detail posted about the project (hence the ‘Open’ in the contest title).

Need some ideas to get you started? We enjoyed the useless machine that used a 7400 NAND gate. You could always build a time piece of some sort like this no-microcontroller clock. Perhaps hardware control like this stepper motor driver is more to your liking?

[Thanks Moderboy]

[Osgeld] built himself a binary clock. He didn’t take the time to explain his project, but he did post beautifully hand-drawn schematics and pictures of the circuit (PDF) as he was building it. We’ve seen clock projects that use mains frequency as the clock source and that’s the route that [Osgeld] chose for his build. He started with a 9-12V AC wall wort as a power input. From there it’s just a matter of using a bridge rectifier to convert to DC, then a 7805 linear regulator to establish a steady 5V rail. A resistor and a couple of diodes allow him to pull the 60 Hz frequency off of the incoming AC, and then use a combination of 4000 and 7400 logic chips to count the pulses and keep track of the time.

Lazarus-64, breadboard game system; certainly sounds like something from the 1980s. We were surprised to find out not only the name, but also all the ICs used are only those available from the retro age of 30 years back (Save for the AVR controlling everything, of course). Even more amazing is how it has 256 flicker free color support, while not using NTSC chips. Which Goes to show that even if there are common solutions out there for cheap, building or compiling your own is not necessarily a bad thing or a waste of time.

There is a whole lot more to Lazarus, including double buffering and VMS, but sadly it appears progress has stopped on the Lazarus-64 breadboard game system, with the last update being last year. But we can still bask in the amazing glow that currently is.

the folks over at OpenSchemes are at it again. This time they’ve cracked open a low end ZerPlus logic analyzer and modified it to function the same as the higher end model. The 16 channel version they purchased appeared to be fully capable of handling the 32 channels of the more expensive model. The installation of the additional components looks like it might be somewhat difficult, but it is certainly cheap.We love seeing things upgraded for cheap. You might recognize OpenSchemes from when they upgraded the DMM tweezers or hacked the USB serial adapters.

[via HackedGadgets]