LiPo Replacement Keeps Portable Scanner In The Action

November 21, 2023 by Dan Maloney 8 Comments

If there’s anything people hate more than being locked into a printer manufacturer’s replacement cartridges, it’s proprietary batteries. Cordless power tools are the obvious example in this space, but there are other devices that insist on crappy battery packs that are expensive to replace when they eventually die.

One such device is the Uniden Bearcat BC296D portable scanner that [Robert Guildig] found for a song at a thrift store, which he recently gave a custom LiPo battery upgrade. It came equipped with a nickel-cadmium battery pack, which even under the best of circumstances has a very limited battery life. Using regular AA batteries wasn’t an option, but luckily the space vacated by the OEM battery pack left a lot of room for mods. Those include a small module with BMS functions and a DC-DC converter, a 2,400 mAh 4.2 V LiPo pillow pack, and a new barrel connector for charging. With the BMS set for six volts and connected right to the old battery pack socket, the scanner can now run for seven hours on a one-hour charge. As a bonus, the LiPo pack should last a few times longer than the NiCd packs, and be pretty cheap to replace when it finally goes too. There’s a video after the hop with all the details.

If you’re looking at a similar battery replacement project, you might want to check out [Arya]’s guide to everything you need to know about lithium-ion circuitry.

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Hackaday Links: November 19, 2023

November 19, 2023 by Dan Maloney 8 Comments

Two RUDs are better than one, right? That might be the line on Saturday morning’s briefly spectacular second attempt by SpaceX to launch their Starship vehicle atop a Super Heavy booster, which ended with the “rapid unscheduled disassembly” of both vehicles. The first attempt, back in April, had trouble from the get-go, including the rapid unscheduled partial disassembly of their Stage Zero launch pad, followed by rapid but completely predictable disassembly of a lot of camera gear and an unfortunate minivan thanks to flying chunks of concrete.

Engineering changes helped keep Stage Zero more or less intact this time, and the Super Heavy booster performed flawlessly — for about three minutes. It was at that point, right after the start of the new “hot staging” process, where Starship’s six engines light before the booster actually drops away, that the problems started. The booster made a rapid flip maneuver to get into the correct attitude for burn-back and landing before disappearing in a massive ball of flame.

Reports are that the flight termination system did the deed, but it’s not yet exactly clear why. Ditto the Starship, which was also snuffed by the FTS after continuing to fly for about another five minutes. Still in all, the SpaceX crew seem to be ecstatic about the results, which is understandable for a company with a “move fast, break things” culture. Nailed it.

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Two-Channel Guitar Stomp Box Makes Momentary Switches Latching

November 19, 2023 by Dan Maloney 12 Comments

When we first saw [Maarten Tromp]’s article about a “momentary latching switch” for guitar effects pedals, we have to admit to being a bit confused. When it comes to push-button switches, “momentary” and “latching” seem to be at odds with each other, with different mechanisms inside the switch to turn one into the other. What gives?

As it turns out, [Maarten]’s build makes perfect sense when you consider the demands of a musical performance. Guitar effects pedals, or “stomp boxes,” are often added to the output of electric guitars and other instruments to change the signals in some musically interesting way. The trouble is, sometimes you only need an effect for a few bars, and the push-on, push-off switches on many effects pedals make that awkward.

[Maarten]’s idea was to build a stomp box with momentary switches that act as inputs to an ATtiny2313 microcontroller rather than directly controlling the effect. That way, a bit of code can determine how long the switch is tapped, and activate a relay to do the actual switching accordingly. A short tap of the button tells the microcontroller to latch the relay closed until another tap comes along; a long press means that the relay is held open only as long as the button is held down.

Yes, he could have used a 555, a fact which [Maarten] readily acknowledges, but with some loss of flexibility; he currently has the threshold set at 250 milliseconds, which works for his performance style. Changing it would be a snap in code, as would toggling the latching logic. A microcontroller also makes expansion from the two-channel setup shown here easier.

Looking for more effects pedal action? We’ve got a bunch — a tube-amp tremolo, an Arduino Mega multipedal, a digital delay line. Take your pick!

Bigfoot Turns Classic Sewing Machine Into A Leather-Eating Monster

November 18, 2023 by Dan Maloney 12 Comments

If you try to sew leather on a standard consumer-grade machine, more often than not you’ll quickly learn its limits. Most machines are built for speed, and trying to get them to punch through heavy material at the low motor speeds often needed for leather work is a lesson in frustration.

How frustrating? Enough so that [Joseph Eoff] expended considerable effort to create this sewing machine speed controller for his nearly century-old Adler sewing machine. The machine was once powered by a foot treadle, which is probably why the project is dubbed “Bigfoot,” but now uses a 230 V universal motor. Such motors don’t deliver much torque when run at low speeds with the standard foot-pedal rheostat control, so [Joseph] worked up an Arduino-based controller with a tachometer for feedback and a high-power PWM driver for the motor.

There are a ton of details in [Joseph]’s post and even more in the original blog article, which is well worth a read, but a couple really stand out. The first is with the tachometer, which uses an off-the-shelf photointerrupter and slotted disc. [Joseph] was displeased with the sensor’s asymmetrical and unreliable output, so he made some modifications to the onboard comparator to square up the signal. Also interesting is the PID loop auto-tuning function he programmed into Bigfoot; press a button and the controller automatically ramps the motor speed up and down and stores the coefficients in memory. Nice!

The short video below shows Bigfoot in action with varying thicknesses of faux leather; there are also some clips in the original article that show the machine dealing with a triple thickness of leather at slow speed and not even breaking a sweat. Hats off to [Joseph] on a solid build that keeps a classic machine in the game. And if you want to get into the textile arts but don’t know where to start, we’ve got you covered.

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Taking A Public Transit Display From Project To Product

November 17, 2023 by Dan Maloney 16 Comments

We’ve noticed an uptick in “project to product” stories lately, which seems like a fantastic trend to us. It means that hackers are turning out projects that really resonate with people, to the degree that taking the leap and scaling up from a one-off to a marketable product is worth the inherent risk. And luckily enough for the rest of us, we get to learn from their experiences.

The latest example of this comes to us from [Stefan Schüller], who from the sound of things only reluctantly undertook the conversion of his LED matrix public transit sign into an actual product. The original project had a lot going for it; it looked fantastic, it was technologically simple, and it provided a valuable service. But as a project, it made certain assumptions and concessions that would cause problems when in the hands of a customer. Chief among these was the physical protection of the fragile LEDs, which could easily shear off the display modules if bumped or dropped. There were also firmware issues, such as access to the backend API that serves the transit data; requiring each customer to sign up for and configure their own API key is a non-starter for a product.

In the article, [Stefan] enumerates a long list of problems that going from project to product raises, as well as how he addressed them. The API issue was solved by implementing his own service, which acts as a middleman between the official API and his customers. A nice plexiglass and sheet-metal frame serves to protect the display, too. Design changes were made as well, not only to provide better functionality but to make manufacturing easier. [Stefan] also relates a tale of woe with regard to getting the display’s app into the app stores, something that few of us have to deal with when we’re just fiddling around with something on the bench.

All in all, [Stefan] does a great job walking us through the trials and tribulations of bringing a product to market. There are similar lessons in this production run scale-up, too, but with an entirely different level of project complexity.

A Canned Ham Ham Antenna

November 16, 2023 by Dan Maloney 29 Comments

If you’d have asked us for odds on whether you could successfully turn a canned ham into an amateur radio antenna, we’d have declined the offer. Now, having seen [Ben Eadie (VE6SFX)]’s “hamtenna” project, we’d look at just about any “Will it antenna?” project with a lot less skepticism than before.

To be painfully and somewhat unnecessarily clear about [Ben]’s antenna, the meat-like product itself is not in the BOM for this build, although he did use it as sustenance. Rather, it was the emptied and cleaned metal can that was the chief component of the build, along with a few 3D printed standoffs and the usual feedline and connectors. This is a slot antenna, a design [Ben] recently experimented with by applying copper foil tape to his car’s sunroof. This time around, the slot was formed by separating the top and bottom of the can using the standoffs and electrically connecting them with a strip of copper tape.

Connected to a stub of coax and a BNC connector, a quick scan with a NanoVNA showed a fantastic 1.26:1 SWR in the center of the 70-cm ham band, and a nearly flat response all the way across the band. Results may vary depending on the size of canned ham you sacrifice for this project; [Ben]’s can measured just about 35 cm around, a happy half-wavelength coincidence. And it actually worked in field tests — he was able to hit a local repeater and got good signal reports. All that and a sandwich? Not too shabby.

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Umbrella Antenna Protects You From Rain, But Not The Way You Think

November 16, 2023 by Dan Maloney 8 Comments

You never know when you’ll be called upon to [MacGyver] your way out of an emergency. We can’t imagine what kind of situation would call for whipping up a satellite ground station for NOAA weather satellites from junk, but hey, it could happen.

And when it does, you’ll be ready — as long as you have an umbrella, some foil tape, and various bits and bobs like wire and an RTL-SDR dongle. That’s what [saveitforparts] used for his field-expedient build, at least in the first instance; as you can imagine, builds like this take a lot of tweaking to get right. The umbrella and foil tape form the main reflector for the antenna, with a pie tin, a scrap of wire, and some random twigs being used to build the antenna’s helical feed. Attached to a SAWbird LNA/filter and an RTL-SDR plugged into a dodgy second-hand phone, he was able to get at least some kind of data from one of the GOES satellites, but it wasn’t great.

Switching the feed to a commercially available log periodic antenna worked much better, with some partial decodes of weather map data. Actually, getting anything at all with a setup like this is impressive enough for us to call it a win. It shows that the umbrella approach to antennas is valid; but then again, we already knew that.

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