Among multimeters one instrument stands far and above the rest. An object desired for its accuracy, resolution and shear engineering beauty. I speak of course of the HP 3458A. That’s right, not Keysight, not even Agilent (though of course it goes by those brands too). The 3458A was released in 1989, when HP was still… well… HP. An elegant meter from a more civilized age. As the HP Journal documents, the 3458A was a significant engineering feat and has remained in production (and largely unchallenged) for the last 26 years.
But what, you might ask, makes the 3458A such a significant and desirable instrument? It’s all in the digits. The 3458A is one of the few 8.5 digit multimeters available. It is therefore sensitive to microvolt deflections on 10 volt measurements. It is this ability to distinguished tiny changes on large signals that sets high precision multimeters apart. Imagine weighing an elephant and being able to count the number of flies that land on its back by the change in weight. The 3458A accomplishes a similar feat.
Continue reading “Nuts About Volts”
For those of us who grew up during TI’s calculator revolution, the concept of reverse polish notation (RPN) might be foreign. For other more worldly calculator users, however, the HP calculator was ubiquitous. Hewlett-Packard peaked (at least as far as calculators are concerned) decades ago and the market has remained dominated by TI since. Lucky for those few holdouts there is now a new microcode emulator of these classic calculators.
Called the NP25 (for Nonpariel Physical), the calculator fully emulates the HP-21, HP-25C and HP-33C. It’s a standalone microcode emulator, which means that these calculators work exactly as well as the original HP calculators of the 70s did. The new calculators, however, are powered by a low power MSP430G2553 processor and presumably uses many, many fewer batteries than the original did. It has an LED display to cut power costs as well, and was built with the goal of being buildable by the average electronics hobbyist.
Even if you didn’t grow up in the 70s with one of these in your desk drawer, it’d still be a great project and would help even the most avid TI user appreciate the fact that you don’t have to use RPN to input data into calculators anymore. Not that there’s anything wrong with that. This isn’t the only calculator we’ve featured here, either, so be sure to check out another free and open calculator for other calculator-based ideas.
Continue reading “Hackaday Prize Entry: The 70s Called. They Want This Calculator”
Hackers, makers, and engineers have long had a love affair with number crunching. Specifically with the machines that make crunching numbers easier. Today it may be computers, smart watches, and smartphones, but that wasn’t always the case. In the 50’s and 60’s, Slide rules were the rage. Engineers would carry them around in leather belt pouches. By the early 70’s though, the pocket calculator revolution had begun. Calculators have been close at hand for hackers and engineers ever since. This week’s Hacklet celebrates some of the best calculator projects on Hackaday.io!
We start with [Joey Shepard] and RPN Scientific Calculator. No equals sign needed here; [Joey] designed this calculator to work with Reverse Polish notation, just like many of HP’s early machines. Stacks are pretty important for RPN calculators, and this one has plenty of space with dual 200 layer stacks. The two main processors are MSP430s from Texas Instruments. The user interface are a 4 line x 20 character LCD and 42 hand wired buttons. The two processors are pretty ingenious. They communicate over a UART. One processor handles the keyboard and display, while the other concentrates on crunching the numbers and storing data in an SRAM. The case for this calculator is made from soldered up copper clad board. It’s mechanically strong especially since [Joey] added a bead of solder along each joint. If you want to learn more about this technique check out this guide on FR4 enclosures.
[Joey] definitely improved his solder skills with this project. Every wire and connection, including the full SRAM address and data bus were wired by hand on proto boards. We especially like the sweet looking laser cut keyboard on this project!
Continue reading “Hacklet 70 – Calculator Projects”
If you look on the back of old, old test equipment, you’ll find a weird-looking connector that’s either labeled IEEE-488, GPIB, or HP-IB. It’s a very old interface designed by HP for their test equipment, and it was licensed to other manufacturers for everything from power supplies to logic analyzers. Hewlett-Packard also made computers and workstations once upon a time, and it’s no surprise this interface also made it into these boxes. They even had external hard drives that operated over the HP-IB interface.
[Chris] has a few of these old computers, and wanted to see if he could emulate one of these HP-IB hard drives. There is a project to emulate these hard drives, but the electrical connection is a bit tricky; you need an IEEE-488 card, and those really aren’t made anymore.
Nevertheless, [Chris] found an old ISA IEEE-488 last year, and installed it in the PC system he’s using for all his retro explorations. After getting the card and cable to fit in the case of his PC, [Chris] connected a real HP-IB disk to his modern computer running HPDrive, made an image, and connected an old HP 150 computer. The image was read by the HP 150, and [Chris] had a vintage computer running off an emulated drive.
The HP 5328 Universal Counter is all the counter you’ll ever need. It’s rugged, does its job well, and like all old HP gear, keeps on going. When it breaks, though, that’s a problem.
[Tom] had an 5328 Universal Counter with a broken Oven Controlled Crystal Oscillator. This is the HP 10544 OCXO and replacements are pretty spendy. Instead of buying a vintage unit, [Tom] decided to make a replacement.
The OXCO in the HP 5328 is just an option. If the frequency counter has this option installed, a 30-pin edge connector in the counter is stuffed with a little PCB. Like all HP gear, the schematics are readily available, and the original OXCO can be quickly reverse engineered.
The design of the replacement is fairly straightforward. A 10MHz OXCO from Oscilloquartz is used, powered from the 28V rail in the 5328 with a simple switching regulator. Apart from that, it’s just an inverter to get the logic levels correct, and a small, multi-turn pot to calibrate the new OXCO. The completed unit is much smaller than the original OXCO option, so it can be plugged directly into the 30-pin card edge slot, leaving the gigantic standoff inside the frequency counter as a reminder of days gone by.
[Roberto] recently discovered a clever way to gain root access to an HP t520 thin client computer. These computers run HP’s ThinPro operating system. The OS is based on Linux and is basically just a lightweight system designed to boot into a virtual desktop image loaded from a server. [Roberto’s] discovery works on systems that are running in “kiosk mode”.
The setup for the attack is incredibly simple. The attacker first stops the virtual desktop image from loading. Then, the connection settings are edited. The host field is filled with garbage, which will prevent the connection from actually working properly. The real trick is in the “command line arguments” field. The attacker simply needs to add the argument “&& xterm”. When the connection is launched, it will first fail and then launch the xterm program. This gives the attacker a command shell running under the context of whichever user the original software is running as.
The next step is to escalate privileges to root. [Roberto] discovered a special command that the default user can run as root using sudo. The “”hpobl” command launches the HP Easy Setup Wizard. Once the wizard is opened, the attacker clicks on the “Thank You” link, which will then load up the HP website in a version of Firefox. The final step is to edit Firefox’s default email program association to xterm. Now when the attacker visits an address like “mailto:firstname.lastname@example.org”, Firefox (running as root) launches xterm with full root privileges. These types of attacks are nothing new, but it’s interesting to see that they still persist even in newer software.
Over the last few years we’ve seen a few commercial products that aim to put an entire PCB fab line on a desktop. As audacious as that sounds, there were a few booths showing off just that at CES last week, with one getting a $50k check from some blog. [Connor] and [Feiran] decided to do the hacker version of a PCB printer: an old HP plotter converted to modern hardware with a web interface with a conductive ink pen.
The plotter in question is a 1983 HP HIPLOT DMP-29 that was, like all old HP gear, a masterpiece of science and engineering. These electronics were discarded (preserved may be a better word) and replaced with modern hardware. The old servo motors ran at about 1.5A each, and a standard H-Bridge chip and beefy lab power supply these motors were the only part of the original plotter that were reused. For accurate positioning, a few 10-turn pots were duct taped to the motor shafts and fed into the ATMega1284p used for controlling the whole thing.
The final iteration of hardware wasn’t exactly what [Connor] and [Feiran] had in mind, but that’s mostly an issue with the terrible conductivity of the conductive ink. They’ve tried to fix this by running the pen over each line five times, but that introduces some backlash. This is the final project for an electrical engineering class, so we’re going to say that’s alright.
Continue reading “Circuit Plotting With An HP Plotter”