From Nanoamps To Gigahertz: The World’s Most Extreme Op Amps

January 6, 2022 by 104 Comments

The operational amplifier, or op amp, is one of the most basic building blocks used in analog circuits. Ever since single-chip op amps were introduced in the 1960s, thousands of different types have been developed, some more successful than others. Ask an experienced analog designer to name a few op amps, and they’ll likely mention the LM324, the TL072, the NE5534, the LM358, and of course the granddaddy of all, the uA741.

If those part numbers don’t mean anything to you, all you need to know is that these are generic components that you can buy anywhere and that will do just fine in the most common applications. You can buy fancier op amps that improve on some spec or another, sometimes by orders of magnitude. But how far can you really push the concept of an operational amplifier? Today we’ll show you some op amps that go way beyond these typical “jellybean” components.

Before we start, let’s define what exactly we mean when we say “operational amplifier”. We’re looking for integrated op amps, meaning a single physical component, that have a differential high-impedance voltage input, a single-ended voltage output, DC coupling, and high gain meant to be used in a feedback configuration. We’re excluding anything made from discrete components, as well as less-general circuits like fixed-gain amplifiers and operational transconductance amplifiers (OTAs).

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New Part Day: The RISC-V Lichee-RV Module And Dock

January 6, 2022 by 47 Comments

Sipeed have been busy leveraging developments in the RISC-V arena, with an interesting, low-cost module they call the Lichee RV. It is based around the Aliwinner D1 SoC (which contains a Pingtou Xuantie C906 for those following Chinese RISC-V processor development) with support for an optional NAND filesystem. This little board uses a pair of edge connectors, similar to the Raspberry Pi CM3 form factor, except it’s based around a pair M.2 connectors instead. The module has USB-C, an SPI LCD interface, as well as a TF card socket on-board, with the remaining interfaces provided on the big edge connector.

The minimalist Allwinner D1-based Lichee RV

So that brings us onto the next Sipeed board, the Lichee RV Dock which is a tiny development board for the module. This breaks out the HDMI, adds USB, a WiFi/Bluetooth module, audio driver, microphone array interface and even a 40-way GPIO connector. Everything you need to build your own embedded cloud-connected device.

Early adopters beware, though, Linux support is still in the early stages of development, apparently with Debian currently the most usable. We’ve not tested one ourselves yet, but it does look like quite useful for those projects with a small budget and not requiring the power-hungry multi-core performance of a Raspberry Pi or equivalents.

We’ve seen the Sipeed MAix M1 AI Module hosted on a Pi Hat a couple of years ago, as well as a NES emulator running on the Sipeed K210. The future for RISC-V is looking pretty good if you ask us!

Thanks [Maarten] for the tip!

Ham Antenna Fits Almost Anywhere

January 6, 2022 by 37 Comments

[G3OJV] knows the pain of trying to operate a ham radio transmitter on a small lot. His recent video shows how to put up a workable basic HF antenna in a small backyard. The center of the system is a 49:1 unun. An unun is like a balun, but while a balun goes from balanced line to an unbalanced antenna, the unun has both sides unbalanced. You can see his explanation in the video below.

The tiny hand-size box costs well under $40 or $50 and covers the whole HF band at up to 200 W. The video shows the inside of the box which, as you’d expect, is a toroid with a few turns of wire.

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Servo Plotter Needs Nothing Exotic

January 5, 2022 by 29 Comments

Although the widespread use of 3D printers has made things like linear bearings and leadscrews more common, you still can’t run down to your local big-box hardware store and get them. However, you can get drawer slides and any hobby shop can sell you some RC servos. That and an Arduino can make a simple and easy plotter. Just ask [JimRD]. You can also watch it do its thing in the video below.

Of course, servos aren’t usually what you use in a plotter. But the slides convert the rotation of the servo into linear motion. One servo for X and one for Y is all you need. Another microservo lifts the pen up and down using a hinge you could also get from a hardware store.

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Haptic Feedback “Rifle” Lets You Take Aim In VR

January 5, 2022 by 25 Comments

There was a time when virtual reality seemed like it would remain in the realm of science fiction at least for the foreseeable future. Then we were blessed with products like the Power Glove and Virtual Boy which seemed to make it more of a reality, if not a clunky and limited one. Now, though, virtual reality is taking more of a center stage as the technology for it improves and more and more games are released. We can see no greater proof of this than the fact that some gamers are building their own custom controllers to interact with the virtual world in more meaningful ways, like this game controller specifically built for first-person shooter games.

The controller is based on an airsoft gun but completely lacks the ability to fire a projectile, instead using the gun as a base for building the controller. In fact, the gun’s operation is effectively reversed in order to immerse the player into the game by using haptic feedback provided by pressurized air. The air is pumped in to what would be the front of the barrel and is discharged through the receiver when a trigger pull is detected in order to generate a recoil effect. The controller includes plenty of other features as well, including the ability to reload ammunition, change the firing mode, and track motion thanks to its pair of integrated Oculus controllers.

All of the parts for this controller are either 3D printed or readily available off-the-shelf, making this an ideal platform for customization and improvement. There’s also a demo game available from Unity which allows for a pretty easy setup for testing. While the controller looks like an excellent way to enjoy an FPS virtual reality experience, if you’re looking for a more general-purpose controller we are also starting to see a lot of development on that end as well.

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Blinking Cursor Turns 54, Hardly Anyone Notices

January 5, 2022 by 27 Comments

In an interesting post on Inverse, [Sarah Wells] does a deep dive into something you probably don’t think about very often: the blinking cursor. You’d assume there wasn’t much to the story. Maybe a terminal manufacturer put a toggle flip flop on the cursor output and it caught on. But the true story is much deeper than that.

We were surprised that the father of the blinking cursor was one guy, [Charles Kiesling]. In a 1967 patent, he described the blinking cursor. An ex-Navy man, [Kiesling’s] patent names his employer at the time, Sperry Rand, where he’d worked since 1955.

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A Simple Touch Probe Made With Basic Tools

January 5, 2022 by 14 Comments
Six points of contact detect any displacement.

LinuxCNC contributor and machining enthusiast [Andy Pugh] is certainly not afraid to try making specialised tools to see how well they work out, and this time he’s been busy making a touch probe (video, embedded below) for checking the accuracy of machining operations and general measuring applications.

These things are not cheap, since they are essentially ‘just’ a switch with a long probe, But, as with anything specialised and machined with tight tolerances, you can understand why they cost what they do.

After inspecting and spending some time reverse-engineering such a unit, [Andy] then proceeded to grab some PEEK bar he had lying around and chuck it into the lathe (get it?). He notes Delrin would be more cost effective for those wishing to reproduce this, but as long as you have the ability to machine it and it’s non-conductive, there are many other options you could try.

Using no special tools other than a collet block (like this one) all the angled holes and slots were made with ease, with the help of a specially 3D-printed mount for the vise. A nice, simple approach, we think!

[Andy] tested the repeatability of the probe, mounted over his CNC-converted Holbrook lathe, reporting a value of 1 um, which seems rather good. Centering of the probe tip within the probe body was off a bit, as you’d expect for something made practically by hand, but that is less of a problem as it would seem, as it results in a fixed offset that can be compensated for in software. Perhaps the next version will have some adjustability to dial that out manually?

The whole assembly is formed from two plastic parts, a handful of ground-finished hardened steel pins, and a big spring. The only part remotely special is an off-the-shelf probe tip. During the electrical hookup, you may notice the use of a self-fluxing verowire pen, which was something this scribe didn’t know existed and has already placed an order for!

The reference 3D model for the design is shared from [Andy]’s Autodesk Drive for your viewing pleasure.

Of course, this isn’t the first DIY touch probe we’ve seen, here’s one for example, and over on Hackaday.IO, here’s an attempt to make one using a piezoelectric transducer.

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