digital

79 Articles

Solar Panel Keeps Cheap Digital Calipers Powered Up

April 20, 2024 by 39 Comments

There’s no doubt that cheap digital calipers are useful, especially when designing 3D-printed parts. Unfortunately, cheap digital calipers are also cheap, and tend to burn through batteries quickly. Sure, you can remove the battery when you’re done using them, but that’s for suckers — winners turn to solar power to keep their calipers always at the ready.

[Johan]’s solar upgrade begins with, unsurprisingly, a solar cell, one that just fits on the back of his digital calipers. Like most of these cheap calipers, this one is powered by a single 1.5 V LR44 button cell, while the polycrystalline solar cell is rated for 5 V, so [Johan] used a red LED as a crude voltage regulator. He also added a stack of fourteen 100 μF SMD capacitors soldered together in parallel. The 1206 devices form a 1,400 μF block that’s smaller than the original button cell so that everything fits in the vacated battery compartment. It’s pretty slick.

Given their agreeable price point, digital calipers are a tempting target for hacking. We’ve seen a ton of them, from accessibility add-ons to WiFi connectivity and even repurposing them for use as DROs. Ever wonder how these things work? We’ve looked at that, too.

Emails Over Radio

April 9, 2024 by 38 Comments

The modern cellular network is a marvel of technological advancement that we often take for granted now. With 5G service it’s easy to do plenty of things on-the-go that would have been difficult or impossible even with a broadband connection to a home computer two decades ago. But it’s still reliant on being close to cell towers, which isn’t true for all locations. If you’re traveling off-grid and want to communicate with others, this guide to using Winlink can help you send emails using a ham radio.

While there are a number of ways to access the Winlink email service, this guide looks at a compact, low-power setup using a simple VHF/UHF handheld FM radio with a small sound card called a Digirig. The Digirig acts as a modem for the radio, allowing it to listen to digital signals and pass them to the computer to decode. It can also activate the transmitter on the radio and send the data from the computer out over the airwaves. When an email is posted to the Winlink outbox, the software will automatically send it out to any stations in the area set up as a gateway to the email service.

Like the cellular network, the does rely on having an infrastructure of receiving stations that can send the emails out to the Winlink service on the Internet; since VHF and UHF are much more limited in range than HF this specific setup could be a bit limiting unless there are other ham radio operators within a few miles. This guide also uses VARA, a proprietary protocol, whereas the HF bands have an open source protocol called ARDOP that can be used instead. This isn’t the only thing these Digirig modules can be used for in VHF/UHF, though. They can also be used for other digital modes like JS8Call, FT8, and APRS.

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Raspinamp: It Really Replicates Questionable Activities Involving Llamas

March 7, 2024 by 22 Comments

In the late 90s as MP3s and various file sharing platforms became more common, most of us were looking for better players than the default media players that came with our operating systems, if they were included at all. To avoid tragedies like Windows Media Center, plenty of us switched to Winamp instead, a much more customizable piece of software that helped pave the way for the digital music revolution of that era. Although there are new, official versions of Winamp currently available, nothing really tops the nostalgia of the original few releases of the software which this project faithfully replicates in handheld form.

The handheld music player uses a standard Raspberry Pi (in this case, a 3B) and a 3.5″ TFT touchscreen display, all enclosed in a clear plastic case. With all of the Pi configuration out of the way, including getting the touchscreen working properly, the software can be set up. It uses QMMP as a media player with a Winamp skin since QMMP works well on Linux systems with limited resources. After getting it installed there’s still some configuration to do to get the Pi to start it at boot and also to fit the player perfectly into the confines of the screen without any of the desktop showing around the edges.

Although it doesn’t use the original Winamp software directly, as that would involve a number of compatibility layers and/or legacy hardware at this point, we still think it’s a faithful recreation of how the original looked and felt on our Windows 98 machines. With a battery and a sizable SD card, this could have been the portable MP3 player many of us never knew we wanted until the iPod came out in the early 00s, and would certainly still work today for those of us not chained to a streaming service. A Raspberry Pi is not the only platform that can replicate the Winamp experience, though. This player does a similar job with the PyPortal instead.

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Pi 5 And SDR Team Up For A Digital Scanner You Can Actually Afford

February 10, 2024 by 27 Comments

Listening to police and fire calls used to be a pretty simple proposition: buy a scanner, punch in some frequencies — or if you’re old enough, buy the right crystals — and you’re off to the races. It was a pretty cheap and easy hobby, all things considered. But progress marches on, and with it came things like trunking radio and digital modulation, requiring ever more sophisticated scanners, often commanding eye-watering prices.

Having had enough of that, [Top DNG] decided to roll his own digital trunking scanner on the cheap. The first video below is a brief intro to the receiver based on the combination of an RTL-SDR dongle and a Raspberry Pi 5. The Pi is set up in headless mode and runs sdrtrunk, which monitors the control channels and frequency channels of trunking radio systems, as well as decoding the P25 digital modulation — as long as it’s not encrypted; don’t even get us started on that pet peeve. The receiver also sports a small HDMI touchscreen display, and everything can be powered over USB, so it should be pretty portable. The best part? Everything can be had for about $250, considerably cheaper than the $600 or so needed to get into a purpose-built digital trunking scanner — we’re looking at our Bearcat BCD996P2 right now and shedding a few tears.

The second video below has complete details and a walkthrough of a build, from start to finish. [Top DNG] notes that sdrtrunk runs the Pi pretty hard, so a heat sink and fan are a must. We’d probably go with an enclosure too, just to keep the SBC safe. A better antenna is a good idea, too, although it seems like [Top DNG] is in the thick of things in Los Angeles, where LAPD radio towers abound. The setup could probably support multiple SDR dongles, opening up a host of possibilities. It might even be nice to team this up with a Boondock Echo. We’ve had deep dives into trunking before if you want more details.

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Recreating The Quadrophonic Sound Of The 70s

February 6, 2024 by 23 Comments

For plenty of media center PCs, home theaters, and people with a simple TV and a decent audio system, the standard speaker setup now is 5.1 surround sound. Left and right speakers in the front and back, with a center speaker and a subwoofer. But the 5.1 setup wasn’t always the standard (and still isn’t the only standard); after stereo was adopted mid-century, audio engineers wanted more than just two channels and briefly attempted a four-channel system called quadrophonic sound. There’s still some media from the 70s that can be found that is built for this system, such as [Alan]’s collection of 8-track tapes. These tapes are getting along in years, so he built a quadrophonic 8-track replica to keep the experience alive.

The first thing needed for a replica system like this is digital quadrophonic audio files themselves. Since the format died in the late 70s, there’s not a lot available in modern times so [Alan] has a dedicated 8-track player connected to a four-channel audio-to-USB device to digitize his own collection of quadrophonic 8-track tapes. This process is destructive for the decades-old tapes so it is very much necessary.

With the audio files captured, he now needs something to play them back with. A Raspberry Pi is put to the task, but it needs a special sound card in order to play back the four channels simultaneously. To preserve the feel of an antique 8-track player he’s cannibalized parts from three broken players to keep the cassette loading mechanism and track indicator display along with four VU meters for each of the channels. A QR code reader inside the device reads a QR code on the replica 8-track cassettes when they are inserted which prompts the Pi to play the correct audio file, and a series of buttons along with a screen on the front can be used to fast forward, rewind and pause. A solenoid inside the device preserves the “clunk” sound typical of real 8-track players.

As a replica, this player goes to great lengths to preserve the essence of not only the 8-track era, but the brief quadrophonic frenzy of the early and mid 70s. There’s not a lot of activity around quadrophonic sound anymore, but 8-tracks are popular targets for builds and restorations, and a few that go beyond audio including this project that uses one for computer memory instead.

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Hackaday Prize 2023: AC Measurements Made Easy

October 12, 2023 by 17 Comments

When working on simple DC systems, a small low-cost multimeter from the hardware store will get the job done well enough. Often they have the capability for measuring AC, but this is where cheap meters can get tripped up. Unless the waveform is a perfect sinusoid at a specific frequency, their simple algorithms won’t be able to give accurate readings like a high-quality meter will. [hesam.moshiri] took this as a design challenge, though, and built an AC multimeter to take into account some of the edge cases that come up when working with AC circuits, especially when dealing with inductive loads.

The small meter, an upgrade from a previous Arduino version that is now based on the ESP32, is capable of assessing root mean square (RMS) voltage, RMS current, active power, power factor, and energy consumption after first being calibrated using the included push buttons. Readings are given via a small OLED screen and have an accuracy rate of 0.5% or better. The board also includes modern design considerations such as galvanic isolation between the measurement side of the meter and the user interface side, each with its own isolated power supply.  The schematics and bill-of-materials are also available for anyone looking to recreate or build on this design.

With the project built on an easily-accessible platform like the ESP32, it would be possible to use this as a base to measure other types of signals as well. Square and triangle waves, as well as signals with a large amount of harmonics or with varying frequencies, all need different measurement techniques in order to get accurate readings. Take a look at this classic multimeter to see what that entails.

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Analog ASIC Design Built Using Digital Standard Cells

September 30, 2023 by 9 Comments

Tiny Tapeout is a way for students, hobbyists, and home gamers to get their own ASICs designs fabbed into real custom chips. Tiny Tapeout 3 was the third running, with designs mandated to be made up of simple digital standard cells. Only, a guy by the name of [Harald Pretl] found a way to make an analog circuit using these digital cells anyway.

In a video on YouTube, [Harald] gave an interview on how he was able to create a temperature sensor within the constraints of the Tiny Tapeout 3 requirements. The sensor has a range of -30 C to 120 C, albeit in a relatively crude resolution of 5 degrees C. The sensor works by timing the discharge of a pre-charged parasitic capacitor, with the discharge current being the subthreshold current of a MOSFET, which is highly dependent on temperature.  [Harald] goes deep into the details on how the design achieves its full functionality using the pre-defined digital cells available in the Tiny Tapeout 3 production run.

You can checkout a deeper breakdown of [Harald]’s design on the submission page. Meanwhile, Tiny Tapeout creator [Matt Venn] gave a great talk on the technology at Hackaday Supercon last year.

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