Low Res Video Card Is Still Amazing Since It’s Made Out Of Logic Chips

July 7, 2019 by Brian Benchoff 33 Comments

[Ben Eater] has been working on building computers on breadboards for a while now, alongside doing a few tutorials and guides as YouTube videos. A few enterprising hackers have already duplicated [Ben]’s efforts, but so far all of these builds are just a bunch of LEDs and switches. The next frontier is a video card, but one only capable of displaying thousands of pixels from circuitry built entirely on a breadboard.

This review begins with a review of VGA standards, eventually settling on an 800×600 resolution display with 60 MHz timing. The pixel clock of this video card is being clocked down from 40 MHz to 10 MHz, and the resulting display will have a resolution of 200×150. That’s good enough to display an image, but first [Ben] needs to get the horizontal timing right. This means a circuit to count pixels, and inject the front porch, sync pulse, and back porch at the end of each horizontal line.

To generate a single horizontal line, [Ben]’s circuit first has to count out 200 pixels, send a blanking interval, then set the sync low, and finally another blanking interval before rolling down to the next line. This is done with a series of 74LS161 binary counters set up to simply count from 0 to 264. To generate the front porch, sync, and back porch, a trio of 8-input NAND gates are set up to send a low signal at the relevant point in a horizontal scan line.

The entire build takes up four solderless breadboards and uses twenty logic chips, but this isn’t done yet: all this confabulation of chips and wires does is step through the pixel data for the horizontal and vertical lines. A VGA monitor detects it’s in the right mode, but there’s no actual data — that’ll be the focus of the next part of this build where [Ben] starts pushing pixels to a monitor.

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The Augmented Reality Breadboard Of The Future

May 27, 2019 by Tom Nardi 15 Comments

You’d be hard pressed to find a carpenter who didn’t own a hammer, or a painter that didn’t have a couple of brushes kicking around. Some tools are simply so fundamental to their respective craft that their ownership is essentially a given. The same could be said of the breadboard: if you’re working with electronics on the hobby or even professional level, you’ve certainly spent a decent amount of time poking components and wires into one of these quintessential prototyping tools.

There’s little danger that the breadboard will loose its relevance going forward, but if [Andrea Bianchi] and her team have anything to say about it, it might learn some impressive new tricks. Developed at the Korean Advanced Institute of Science and Technology, VirtualComponent uses augmented reality and some very clever electronics to transform the classic breadboard into a powerful mixed-reality tool for testing and simulating circuits. It’s not going to replace the $3 breadboard you’ve got hiding at the bottom of your tool bag, but one day it might be standard equipment in electronics classrooms.

The short version is that VirtualComponent is essentially a dynamic breadboard. Holes in the same row are still electrically linked like in the classic breadboard, but with two AD75019 cross-point switch arrays and an Arduino in the base, it has the ability to virtually “plug in” components at arbitrary locations as selected by the user. So rather than having to physically insert a resistor, the user can simply tell the software to connect a resistor between two selected holes and the cross-point array will do the rest.

What’s more, many of those components can be either simulated or at least augmented in software. For example, by using AD5241 digital potentiometers, VirtualComponent can adjust the value of the virtual resistor. To provide variable capacitance, a similar trick can be pulled off using an array of real capacitors and a ADG715 digital switch to connect them together; essentially automating what the classic “Decade Box” does. In the demonstration video after the break, this capability is extended all the way out to connecting a virtual function generator to the circuit.

The whole system is controlled by way of an Android tablet suspended over the breadboard. Using the tablet’s camera, the software provides an augmented reality view of both the physical and virtual components of the circuit. With a few taps the user can add or edit their virtual hardware and immediately see how it changes the behavior of the physical circuit on the bench.

People have been trying to improve the breadboard for years, but so far it seems like nothing has really stuck around. Given how complex VirtualComponent is, they’ll likely have an even harder time gaining traction. That said, we can’t help but be excited about the potential augmented reality has for hardware development.

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Paperclip Breadboard

May 21, 2019 by Al Williams 28 Comments

TV’s MacGyver would love the breadboard arrangement we saw recently: it uses paperclips and crimping to make circuits that can be more or less permanent with no soldering. The basic idea is simple. A cardboard base has a piece of paper affixed. Metal paperclips are bent straight and glued to the paper using PVA glue (you know, like ordinary Elmer’s; hot glue would probably work, too). You could probably salvage wires out of old house wiring that would work for this, too.

The scheme uses two sizes of paper clips. Large ones are made straight and form the rails, while small paperclips make connections. The rails are bent to have a little “ear” that pushes into the cardboard base to hold them still. A little glue stabilizes them. The ears poke out the back, so the author suggests covering them with duct tape, hot glue, or another piece of cardboard. Using the top of a shoebox would also solve the problem.

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CPU Made From 74HC Chips Is A Glorious Mess

May 9, 2019 by Inderpreet Singh 35 Comments

Did you ever start a project that you felt gained a life of its own? This project by [Paulo Constantino] is an entire CPU named dreamcatcher on breadboards, and is a beautiful jungle of digital. On top of that, it works to connect to an analog VGA display. How cool is that!

Designing an ALU and then a CPU is a typical exercise for students of digital design and is done using VerilogHDL or VHDL. It involves creating an ALU that can add, subtract etc while a control unit manages data moves and the like. There is also a memory fetch and instruction decode made up of de-mulitiplexers and a bunch of flip-flops that make up registers and flags. They are as complex as they sound if not more.

[Paulo Constantino] went ahead and designed the whole thing in Eagle as a schematic using 74HC logic chips. To build it though instead of a PCB he used breadboards. Everything from bus decoders to controlling an external VGA display is done using jumper wires. We did cover a video on the project a while back, but this update adds a video card interface to the build.

The CPU updates the display buffer on the VGA card, and in the video below shows the slow and steady update. The fact that the jungle of wires can drive a display is awesome. He has since started working on a 16-bit version of the processor and we’d love to see someone take it up a notch.

For those more accustomed to the PCB, the Z80 membership card project is a great build for 8-bit computer fans.

Thanks to [analog engineer] for the tip.

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A Breadboard Power Supply That’s More Universal Than Most

April 20, 2019 by Brian Benchoff 50 Comments

A favorite project of ours is the humble breadboard power supply. Yes, you can still prototype on breadboards, no, you don’t need an entire bench power supply to prototype on one, and every breadboard made in the last forty years has had the same pattern of holes. There’s plenty of opportunity to improve the breadboard power supply.

One of the best ones we’ve seen yet comes from [John Loeffler]. It’s a simple, constant voltage power supply that’s variable from 0.6 V all the way up to 12 V. It’s powered through a micro USB port, and you get 3.3 V and 5 V rails automagically. There’s even voltage indication.

The mechanical design of this power supply is simple enough, with pins that plug into the detachable power rails on either side of the breadboard. Where it gets interesting is the voltage indication. There’s a resistor ladder and a series of LEDs to indicate the voltage on the variable side of this power supply. Add in some modern switched mode power supply based on the MIC5225 series of chips (a popular regulator that’s very nice for the price) and you have a completely functional power supply hanging off a breadboard.

While it’s not a really nice rack mounted bench power supply that weighs a lot, or even one of the cheapo bench supplies, this does fulfill a need. Sometimes you just need a simple power supply for a breadboard, and this is one of the best ones we’ve seen yet.

A Nearly Practical 6502 Breadboard Computer

April 19, 2019 by Tom Nardi 21 Comments

Over the years we’ve seen a number of homebrew 6502 computers assembled with little more than a breadboard, a sack full of jumper wires, and an otherworldly patience that would make a Buddhist Monk jealous. Anyone who takes the time to assemble a fully functional computer on a half-dozen breadboards lined up on their workbench will always be a superstar in our book.

While we’re still too lazy to attempt one of these builds ourselves, we have to admit that the Vectron 64 by [Nick Bild] looks dangerously close to something you might be able to pull off within a reasonable amount of time. It’s still an incredible amount of work, but compared to some of the other projects we’ve seen, this one manages to keep the part count relatively low thanks to the use of a simple 16×2 LCD for output and user input provided by a PS/2 keyboard. You won’t be playing Prince of Persia on it, but at least you might be able to finish it in a weekend.

The computer is clocked at 1 MHz, and features 32KB RAM
along with 32KB EEPROM. That should be enough for anyone. [Nick] also points out he tried to use era-appropriate 7400 series ICs wherever possible, so no worries about historical revisionism here. If you’re looking for a design that somebody could have potentially knocked together back in the 1970s, this one would get you fairly close.

The astute reader might notice there’s no removable media in this build, and may be wondering how one loads programs. For that, [Nick] allowed himself a bit of modern convenience and came up with a scheme that allows an Arduino (or similar microcontroller) to connect up to the computer’s 28C256-15 EEPROM. With a Python script running on your “real” computer, you can write a new ROM image directly to the chip. He’s included the source code for a simple program which will write whatever you type on the keyboard out on the LCD, which should give you a good framework for writing additional software.

If you’re looking for a bigger challenge, don’t worry. We’ve covered 6502 breadboard computers that will make your eyes water. Incidentally, this isn’t the first time we’ve seen a similar LCD used for one of these computers, so looks like there’s no shame in sneaking in modern parts where it makes sense.

Hexagons – The Crazy New Breadboard

April 6, 2019 by Bryan Cockfield 11 Comments

A breadboard is a great prototyping tool for verifying the sanity of a circuit design before taking the painstaking effort of soldering it all together permanently. After all, a mistake in this stage can cost a lot of time and possibly material, so it’s important to get it right. [daverowntree] wasn’t fully satisfied with the standard breadboard layout though, with fixed rows and columns. While this might work for most applications, he tried out a new type of prototyping board based on hexagons instead.

The design philosophy here revolves around tessellations, a tiling method for connecting the various components on this unique breadboard rather than using simple rows. The hexagons are tessellated across the board, allowing for some unique combinations that might make it slightly more complicated, but can have some benefits for other types of circuits such as anything involving the use of a three-wire device like a transistor.

The post is definitely worth a read, as [daverowntree] goes through several examples of this method of prototyping where the advantages are shown, like a voltage follower circuit and some other circuits involving transistor biasing. If you’re OK with the general design of breadboards, though, and just wished you didn’t have to do anything after the prototyping stage, we’ve got some help for you there as well.