Inside the vintage 74181 ALU chip: how it works and why it’s so strange

The 74181 ALU (arithmetic/logic unit) chip powered many of the minicomputers of the 1970s: it provided fast 4-bit arithmetic and logic functions, and could be combined to handle larger words, making it a key part of many CPUs. But if you look at the chip more closely, there are a few mysteries. It implements addition, subtraction, and the Boolean functions you'd expect, but why does it provide several bizar ...

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5V Power Supply Atop a 9V Battery

I have a $500 Rigol DP832 programmable triple-output power supply sitting on my bench, yet I built a 5V regulator to sit atop a 9V battery for some reason. Perhaps it’s more portable, or cheap enough to toss in with the rest of the project it is powering, or maybe the bench power supply is just overkill. Or maybe, just maybe, I saw other people making them and I thought it would be cool to build myself. Two ...

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Analyzing the vintage 8008 processor from die photos: its unusual counters

The revolutionary Intel 8008 microprocessor is 45 years old today (March 13, 2017), so I figured it's time for a blog post on reverse-engineering its internal circuits. One of the interesting things about old computers is how they implemented things in unexpected ways, and the 8008 is no exception. Compared to modern architectures, one unusual feature of the 8008 is it had an on-chip stack for subroutine ca ...

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Analog Discovery USB isolation

Intro Back when I was deverloping the PSU burner, I wanted to have the Analog Discovery isolated from the common ground, to avoid noise and other issues. Since I did not have a way to do this, I ended up using a laptop on battery for measurements. But for long term, I needed to have this isolation. Unfortunately, things that can isolate USB at 480Mbps or faster are too expensive to justify. The solution The ...

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RFM69 output power

As I was mentioning in my 1000.1000 Hardwareselection, I have opted for the cool RFM69HW radio module. Weirdly enough, in quite a few sources (big distributor and ebay) the higher power HW module is cheaper. So there ie no reason not to get the higher power module, given quantity discounts. But I want it to operate at lower power most of times. The datasheet does not show any differences at lower power, so ...

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YouTube Subscriber Counter With ESP8266

I was inspired by the Play Button awards YouTube sends out for subscriber milestones and whipped up a simple circuit using an ESP8266 wifi board and seven segment display to show off my realtime subscriber count. This is a great IoT beginner project, with just a little soldering and a code personalization required to make it work for your own account. Before attempting this project, you should be generally ...

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Designing Electronics in Spain

FONA808 USB Interface 1 Reply Hi! First of all, Happy New Year 2017! I hope all of yours starts the new year with good intentions. The mine one is write frequently here. Family and work don’t let me much free time but I’ll try it! For several months I’m working with FONA808 modules from Adafruit to make a portable, web-based locating system. This modules are based on the SIM808 module from SIMCOM manufactur ...

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GEN4 3.2”, THE NEW INTELLIGENT DISPLAY MODULES

4D Systems, the manufacturer of intelligent graphics solutions, has announced a new 3.2” smart display module as part of the ‘ gen4 ’ series, which had been designed specifically for ease of integration and use, with careful consideration for space requirements and functionality. These modules features a 3.2” color TFT display with options for Cover Lens Bezel (CLB), Resistive Touchand Capacitive Touch. The ...

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How to Read Your First Autodesk EAGLE Schematic Like a Pro in 3 Easy Steps

The schematic forms the building block of every electrical circuit, and even if you aren’t designing one yourself, knowing how to read one is invaluable. And with some schematic reading knowledge in hand, you’ll be able to design, build and ultimately troubleshoot your way through your design logic before heading on to your PCB layout. But how in the world do you go about reading a schematic if it’s your fi ...

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CTRL, THE INDUSTRIAL ROBOT ON YOUR DESKTOP

CTRL the robot is a desktop-sized robot arm that can do a lot! It enables your computer to perform manipulation of real objects via software and gives you access to technology that has been locked away in large corporations factories. CTRL was launched on a Kickstarter campaign that unfortunately didn’t reach its goal of AU$ 215,000. The early bird product was sold for AU$ 699 (~ $540) and you were able to ...

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