Recreating The Quadrophonic Sound Of The 70s

February 6, 2024 by Bryan Cockfield 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 Bryan Cockfield 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 Lewin Day 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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Polaroid Develops Its Pictures Remotely

August 16, 2023 by Bryan Cockfield 8 Comments

For those who didn’t experience it, it’s difficult to overstate the cultural impact of the Polaroid camera. In an era where instant gratification is ubiquitous, it’s easy to forget that there was a time when capturing a photograph meant waiting for film to be developed or relying on the meticulous art of darkroom processing. Before the era of digital photography, there was nothing as close to instant as the Polaroid. [Max] is attempting to re-capture that feeling with a modified Polaroid which instantly develops its pictures in a remote picture frame.

The build is based on a real, albeit non-functional, Polaroid Land Camera. Instead of restoring it, a Raspberry Pi with a camera module is placed inside the camera body and set up to capture pictures. The camera needs to connect to a Wi-Fi network before it can send its pictures out, though, and it does this automatically when taking a picture of a QR code. When a picture is snapped, it sends it out over the Internet to wherever the picture frame is located, which has another Raspberry Pi inside connected to an e-ink screen. Once a picture is taken on the camera it immediately shows up in the picture frame.

To help preserve the spirit of the original Polaroid, at no point is an image saved permanently. Once it is sent to the frame, it is deleted from the camera, and the next picture taken overwrites the last. And, for those who are only familiar with grayscale e-ink displays as the integral parts of e-readers, there have been limited options for color displays for a while now, as we saw in this similar build which was painstakingly built into a normal-looking picture frame as part of an attempted family prank.

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Ban On Physical Mail Slated For NYC Jails, Which Could Go Digital Instead

February 13, 2023 by Lewin Day 50 Comments

Prison is a scary place, very much by design. It’s a place you end up when convicted of crimes by the judicial system, or in some cases, if you’re merely awaiting trial. Once you go in as a prisoner, general freedom and a laundry list of other rights are denied to you. New York City is the latest in a long list of municipalities looking to expand that list to include a ban on inmates receiving physical mail.

To achieve this, prisons across the US are instead switching to digital-only systems, which would be run by a private entity. Let’s look at the how, what, and why of this contentious new idea.

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MikroLeo, A 4-Bit Retro Learning Platform

November 27, 2022 by Dave Rowntree 23 Comments

MikroLeo is a discrete TTL logic-based microcomputer intended for educational purposes created by [Edson Junior Acordi], an Electronics Professor at the Brazilian Federal Institute of Paraná, Brazil. The 4-bit CPU has a Harvard RISC architecture built entirely from 74HCT series logic mounted on a two-sided PCB using only through-hole parts. With 2K words of instruction RAM and 2K words of addressable RAM, the CPU has a similar resource level to comparable machines of old, giving students a feel for how to work within tight constraints.

Simulation of the circuit is possible with digital, with the dedicated PCB designed with KiCAD, so there should be enough there to get cracking with it. Four 4-bit IO ports make interfacing easy, with dedicated INput and OUTput instructions for the purpose. An assembler, compiler, and emulator are all being worked on (as far as we can tell) so keep an eye out for that, if this project is of interest to you.

We like computers a bit around these parts, the “hackier” and weirder the better. Even just in the 4-bit retro space, we’ve seen so many, from those built around ancient ALU chips to those built from discrete transistors and diodes, but you don’t need to go down that road, an emulation platform can scratch that retro itch, without the same level of pain.

Trinocular Lens Makes Digital Wigglegrams Easier To Take

October 30, 2022 by Dan Maloney 13 Comments

Everyone likes a good animated GIF, except for some Hackaday commenters who apparently prefer to live a joyless existence. And we can’t think of a better way to celebrate moving pictures than with a 3D printed trinocular camera that makes digital Wigglegrams a snap to create.

What’s a Wigglegram, you say? We’ve seen them before, but the basic idea is to take three separate photographs through three different lenses at the same time, so that the parallax error from each lens results in three slightly different perspectives. Stringing the three frames together as a GIF later results in an interesting illusion of depth and motion. According to [scealux], the inspiration for building this camera came from photographer [Kirby Gladstein]’s work, which we have to admit is pretty cool.

While [Kirby] uses a special lenticular film camera for her images, [scealux] decided to start his build with a Sony a6300 mirrorless digital camera. A 3D printed lens body with a focusing mechanism holds three small lenses which were harvested from disposable 35 mm film cameras — are those still a thing? Each lens sits in front of a set of baffles to control the light and ensure each of the three images falls on a distinct part of the camera’s image sensor.

The resulting trio of images shows significant vignetting, but that only adds to the charm of the finished GIF, which is created in Photoshop. That’s a manual and somewhat tedious process, but [scealux] says he has some macros to speed things up. Grainy though they may be, we like these Wigglegrams; we don’t even hate the vertical format. What we’d really like to see, though, is to see everything done in-camera. We’ve seen a GIF camera before, and while automating the post-processing would be a challenge, it seems feasible.

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