ESP32 Video Tricks Hack Chat with bitluni

Join us Wednesday at noon Pacific time for the ESP32 Video Tricks Hack Chat!

The projects that bitluni works on have made quite a few appearances on these pages over the last couple of years. Aside from what may or may not have been a street legal electric scooter, most of them have centered around making ESP32s do interesting tricks in the analog world. He’s leveraged the DACs on the chip to create an AM radio transmitter, turned an oscilloscope into a video monitor, and output composite video. That last one was handy for turning a Sony Watchman into a retro game console. He’s also found ways for the ESP32 to output VGA signals. Looks like there’s no end to what he can make the versatile microcontroller do.

Although the conversation could (and probably will) go anywhere, we’ll start with video tricks for the ESP32 and see where it goes from there. Possible topics include:

  • Tricks for pushing the ESP32 DACs to their limits;
  • When to use an external DAC;
  • Optimizing ESP32 code by running on separate cores; and
  • What about HDMI on the ESP32?

You are, of course, encouraged to add your own questions to the discussion. You can do that by leaving a comment on the ESP32 Video Tricks Hack Chat and we’ll put that in the queue for the Hack Chat discussion.

join-hack-chatOur Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, March 27, at noon, Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

Simple Timer Evolves into Custom Kid’s Watch

Sporting a new wristwatch to school for the first time is a great moment in a kid’s life. When it’s a custom digital-analog watch made by your dad, it’s another thing altogether.

As [Chris O’Riley] relates, the watch he built for his son [Vlad] started out as a simple timer for daily toothbrushing, a chore to which any busy lad pays short shrift unless given the proper incentive. That morphed into an idea for a general purpose analog timepiece with LEDs taking the place of hands. [Chris] decided that five-minute resolution was enough for a nine-year-old, which greatly reduced the number of LEDs needed. An ATtiny841 tells a 28-channel I2C driver which LEDs to light up, and an RTC chip keeps [Vlad] on schedule. The beautiful PCB lives inside a CNC machined aluminum case; we actually commented to [Chris] that the acrylic prototype looked great by itself, but [Vlad] wanted metal. The watch has no external buttons; rather, the slightly flexible polycarbonate crystal bears against a PCB-mounted pushbutton to control functions.

With a snappy wristband, [Vlad] will be rolling fancy on the schoolyard. It’s a great looking piece that needed a wide range of skills to execute, as all watches do. Check out some other watch builds, like this lovely pure analog, another digital-analog hybrid, or this pocket watch that packs an Enigma machine inside.

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FPGA Makes Digital Analog Computer

When you think of analog computing, it’s possible you don’t typically think of FPGAs. Sure, a few FPGAs will have specialized analog blocks, but usually they are digital devices. [Bruce Land] — a name well-known to Hackaday — has a post about building a digital differential analyzer using an FPGA and it is essentially an analog computer simulated on the digital fabric of an FPGA.

Whereas traditional analog computers use operational amplifiers to do mathematical integration, on the FPGA [Land] uses digital summers The devices simulate a system of differential equations, which can be nonlinear.

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Continuous Computing The Analog Way

When your only tool is a hammer, everything starts to look like a nail. That’s an old saying and perhaps somewhat obvious, but our tools do color our solutions and sometimes in very subtle ways. For example, using a computer causes our solutions to take a certain shape, especially related to numbers. A digital computer deals with numbers as integers and anything that isn’t is actually some representation with some limit. Sure, an IEEE floating point number has a wide range, but there’s still some discrete step between one and the next nearest that you can’t reduce. Even if you treat numbers as arbitrary text strings or fractions, the digital nature of computers will color your solution. But there are other ways to do computing, and they affect your outcome differently. That’s why [Bill Schweber’s] analog computation series caught our eye.

One great example of analog vs digital methods is reading an arbitrary analog quantity, say a voltage, a temperature, or a shaft position. In the digital domain, there’s some converter that has a certain number of bits. You can get that number of bits to something ridiculous, of course, but it isn’t easy. The fewer bits, the less you can understand the real-world quantity.

For example, you could consider a single comparator to be a one-bit analog to digital converter, but all you can tell then is if the number is above or below a certain value. A two-bit converter would let you break a 0-3V signal into 1V steps. But a cheap and simple potentiometer can divide a 0-3V signal into a virtually infinite number of smaller voltages. Sure there’s some physical limit to the pot, and we suppose at some level many physical values are quantized due to the physics, but those are infinitesimal compared to a dozen or so bits of a converter. On top of that, sampled signals are measured at discrete time points which changes certain things and leads to effects like aliasing, for example.

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Old Wattmeter Uses Magnetics To Do the Math

Measuring power transfer through a circuit seems a simple task. Measure the current and voltage, do a little math courtesy of [Joule] and [Ohm], and you’ve got your answer. But what if you want to design an instrument that does the math automatically? And what if you had to do this strictly electromechanically?

That’s the question [Shahriar] tackles in his teardown of an old lab-grade wattmeter. The video is somewhat of a departure for him, honestly; we’re used to seeing instruments come across his bench that would punch a seven-figure hole in one’s wallet if acquired new. These wattmeters are from Weston Instruments and are beautiful examples of sturdy, mid-century industrial design, and seem to have been in service until at least 2013. The heavy bakelite cases and sturdy binding posts for current and voltage inputs make it seem like the meters could laugh off a tumble to the floor.

But as [Shahriar] discovers upon teardown of a sacrificial meter, the electromechanical movement behind the instrument is quite delicate. The wattmeter uses a moving coil meter much like any other panel meter, but replaces the permanent magnet stator with a pair of coils. The voltage binding posts are connected to the fine wire of the moving coil through a series resistance, while the current is passed through the heavier windings of the stator coils. The two magnetic fields act together, multiplying the voltage by the current, and deflect a needle against a spring preload to indicate the power. It’s quite clever, and the inner workings are a joy to behold.

We just love looking inside old electronics, and moving coil meters especially. They’re great gadgets, and fun to repurpose, too.

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Analog Clock Goes Digital, or Vice Versa

Designing a good clock takes a lot of considerations. It’s not just hands, faces, and numbers anymore; there are also word clocks, electronic clocks, marble clocks, or water clocks, and just about anything else imaginable can be used to tell time. Of course, electronic clocks are great for their versatility, and this one shows off an analog-looking clock that is (of course) digital, leveraging all of the perks of analog with all of the upsides of digital electronics.

One of the key design considerations that [Sasa] had while building this piece was that it needed to be silent. LEDs certainly fit that description, so the decision was made to go with an WS2812b ring. It runs using a STM ST32F103 Nucleo board (and a cheaper version of it in later versions of this clock) which shows a red LED for the current hour, yellow LEDs for the traditional analog clock divisions, a green LED for the current minute, and glows the rest of the LEDs up to the current minute with a rainbow pattern.

This is a really clean, simple build with good design at its core, and would be easy to replicate if you’re looking for an eye-catching clock to build. As a bonus, all of the schematics and code are available on the project site, so everything you need is there. If you’re looking for more inspiration, there are some clocks that are even more unique, like this marble clock that is a work of art — but is anything but silent.

Revive that old Analog Cell Phone with SDR

With the latest and greatest 5G cellular networks right around the corner, it can be difficult to believe that it wasn’t so long ago that cell phones relied on analog networks. They aren’t used anymore, but it might only take a visit to a swap meet or flea market to get your hands on some of this vintage hardware. Of course these phones of a bygone era aren’t just impractical due to their monstrous size compared to modern gear, but because analog cell networks have long since gone the way of the floppy disk.

But thanks to the efforts of [Andreas Eversberg] those antique cell phones may live again, even if it’s only within the radius of your local hackerspace. His software allows the user to create a functioning analog base station for several retro phone networks used in Europe and the United States, such as AMPS, TACS, NMT, Radiocom, and C450. You can go the old school route and do it with sound cards and physical radios, or you can fully embrace the 21st century and do it all through a Software Defined Radio (SDR); in either event, calls to the base station and even between multiple mobile devices is possible with relatively inexpensive hardware.

[Andreas] has put together exceptional documentation for this project, which starts with a walk through on how you can setup your DIY cell “tower” with traditional radios. He explains that amateur radios are a viable option for most of the frequencies used, and that he had early success with modifying second-hand taxi radios. He even mentions that the popular BaoFeng handheld radios can be used in a pinch, though not all the protocols will work due to distortion in the radio.

If you want to take the easy way out, [Andreas] also explains how to replace the radios with a single SDR device. This greatly simplifies the installation, and turns a whole bench full of radios and wires into something you can carry around in your pack if you were so inclined. His software has specific options to use the LimeSDR and LimeSDR-Mini, but you should be able to use other devices with a bit of experimentation.

We’ve previously reviewed the LimeSDR-Mini hardware, as well as covered its use in setting up DIY GSM networks.