There are a number of metal cylinders displayed in a line. Each cylinder has a rectangular brass plate mounted to each end, and these brass plates stand upright, with the metal cylinders held horizontally between them.

Home-casting Thermoelectric Alloys

May 16, 2025 by No comments

If you want to convert heat into electrical power, it’s hard to find a simpler method than a thermoelectric generator. The Seebeck effect means that the junction of two dissimilar conductors will produce a voltage potential when heated, but the same effect also applies to certain alloys, even without a junction. [Simplifier] has been trying to find the best maker-friendly thermoelectric alloys, and recently shared the results of some extensive experimentation.

The experiments investigated a variety of bismuth alloys, and tried to determine the effects of adding lead, antimony, tin, and zinc. [Simplifier] mixed together each alloy in an electric furnace, cast it into a cylindrical mold, machined the resulting rod to a uniform length, and used tin-bismuth solder to connect each end to a brass electrode. To test each composition, one end of the cylinder was cooled with ice while the other was held in boiling water, then resistance was measured under this known temperature gradient. According to the Wiedemann-Franz law, this was enough information to approximate the metal’s thermal conductivity.

Armed with the necessary data, [Simplifier] was able to calculate each alloy’s thermoelectric efficiency coefficient. The results showed some useful information: antimony is a useful additive at about 5% by weight, tin and lead created relatively good thermoelectric materials with opposite polarities, and zinc was useful only to improve the mechanical properties at the expense of efficiency. Even in the best case, the thermoelectric efficiency didn’t exceed 6.9%, which is nonetheless quite respectable for a homemade material.

This project is a great deal more accessible for an amateur than previous thermoelectric material research we’ve covered, and a bit more efficient than another home project we’ve seen. If you just want to get straight to power generation, check out this project.

Internals of ding-dong doorbell.

Wireless Doorbell Extension Features Home-Wound Coil

May 16, 2025 by 4 Comments

Today in the it’s-surprising-that-it-works department we have a ding dong doorbell extension from [Ajoy Raman].

What [Ajoy] wanted to do was to extend the range of his existing doorbell so that he could hear it in his workshop. His plan of attack was to buy a new wireless doorbell and then interface its transmitter with his existing doorbell. But his approach is something others might not have considered if they had have been tasked with this job, and it’s surprising to learn that it works!

What he’s done is wrap a new coil around the ding dong doorbell’s solenoid. When the solenoid activates, a small voltage is induced into the coil. This then gets run into the wireless doorbell transmitter power supply (instead of its battery) via a rectifier diode and a filter capacitor. The wireless doorbell transmitter — having also had its push-button shorted out — operates for long enough from this induced electrical pulse to transmit the signal to the receiver. To be clear: the wireless transmitter is fully powered by the pulse from the coil around the solenoid. Brilliant! Nice hack!

We weren’t sure how reliable the transmitter would be when taken out of the lab and installed in the house so we checked in with [Ajoy] to find out. It’s in production now and operating well at a distance of around 50 feet!

Of course we’ve published heaps of doorbell hacks here on Hackaday before, such as this Bluetooth Low Energy (BLE) doorbell and this light-flashing doorbell. Have you hacked your own doorbell? Let us know on the tips line!

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Not A Sewing Machine: A Multimedia Briefcase

May 15, 2025 by 2 Comments

When you think of Singer, you usually think of sewing machines, although if you are a history buff, you might remember they diversified into calculators, flight simulation, and a few other odd businesses for a while. [Techmoan] has an unusual device from Singer that is decidedly not a sewing machine. It is a 1970s-era multimedia briefcase called the Audio Study Mate. This odd beast, as you can see in the video below, was a cassette player that also included a 35mm filmstrip viewer. Multimedia 1970s-style!

The film strip viewer is a bright light and a glass screen with some optics. You have to focus the image, and then a button moves the film one frame. However, that’s for manual mode. However, the tape could encode a signal to automatically advance the frame. That didn’t work right away.

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Voyager 1’s Primary Thrusters Revived Before DSN Command Pause

May 15, 2025 by 16 Comments

As with all aging bodies, clogged tubes form an increasing issue. So too with the 47-year old Voyager 1 spacecraft and its hydrazine thrusters. Over the decades silicon dioxide from an aging rubber diaphragm in the fuel tank has been depositing on the inside of fuel tubes. By switching between primary, backup and trajectory thrusters the Voyager team has been managing this issue and kept the spacecraft oriented towards Earth. Now this team has performed another amazing feat by reviving the primary thrusters that had been deemed a loss since a heater failure back in 2004.

Unlike the backup thrusters, the trajectory thrusters do not provide roll control, so reviving the primary thrusters would buy the mission a precious Plan B if the backup thrusters were to fail. Back in 2004 engineers had determined that the heater failure was likely unfixable, but over twenty years later the team was willing to give it another shot. Analyzing the original failure data indicated that a glitch in the heater control circuit was likely to blame, so they might actually still work fine.

To test this theory, the team remotely jiggled the heater controls, enabled the primary thrusters and waited for the spacecraft’s star tracker to drift off course so that the thrusters would be engaged by the board computer. Making this extra exciting was scheduled maintenance on the Deep Space Network coming up in a matter of weeks, which would troubleshooting impossible for months.

To their relief the changes appears to have worked, with the heaters clearly working again, as are the primary thrusters. With this fix in place, it seems that Voyager 1 will be with us for a while longer, even as we face the inevitable end to the amazing Voyager program.

Automatic Transmission For Manual Transportation

May 15, 2025 by 18 Comments

The drivetrain of most modern bicycles has remained relatively unchanged for nearly a century. There have been marginal upgrades here and there like electronic shifting but you’ll still mostly see a chain with a derailleur or two. [Matthew] is taking a swing at a major upgrade to this system by replacing the front derailleur with a torque converter, essentially adding an automatic transmission to his bicycle.

Most of us will come across a torque converter in passenger vehicles with automatic transmissions, but these use fluid coupling. [Matthew] has come up with a clever design that uses mechanical coupling instead using a ratchet and pawl mechanism. There are two gear ratios here, a 1:1 ratio like a normal bicycle crank and a 1.5:1 ratio that is automatically engaged if enough torque is applied to the pedals. This means that if a cyclist encounters a hill, the gear automatically shifts down to an easier gear and then will shift back once the strenuous section is finished.

[Matthew] machined all the parts for this build from scratch, and the heavy-duty solid metal parts are both impressive but also show why drivetrains like this haven’t caught on in the larger bicycling world since they’re so heavy. There have been some upgrades in internally geared hubs lately though, which do have a number advantages over traditional chain and derailleur-based bikes with the notable downside of high cost, and there have been some other interesting developments as well like this folding mechanical drivetrain and this all-electric one.

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Exposed inner copper on multilayer PCB. (Credit: mikeselectricstuff, YouTube)

LACED: Peeling Back PCB Layers With Chemical Etching And A Laser

May 15, 2025 by 7 Comments

Once a printed circuit board (PCB) has been assembled it’s rather hard to look inside of it, which can be problematic when you have e.g. a multilayer PCB of an (old) system that you really would like to dissect to take a look at the copper layers and other details that may be hidden inside, such as Easter eggs on inner layers. [Lorentio Brodeso]’s ‘LACED’ project offers one such method, using both chemical etching and a 5 Watt diode engraving laser to remove the soldermask, copper and FR4 fiberglass layers.

This project uses sodium hydroxide (NaOH) to dissolve the solder mask, followed by hydrogen chloride (HCl) and hydrogen peroxide (H2O2) to dissolve the copper in each layer. The engraving laser is used for the removing of the FR4 material. Despite the ‘LACED’ acronym standing for Laser-Controlled Etching and Delayering, the chemical method(s) and laser steps are performed independently from each other.

This makes it in a way a variation on the more traditional CNC-based method, as demonstrated by [mikeselectricstuff] (as shown in the top image) back in 2016, alongside the detailed setup video of how a multi-layer PCB was peeled back with enough resolution to make out each successive copper and fiberglass layer.

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Mylar Space Blankets As RF Reflectors

May 15, 2025 by 5 Comments

Metalized Mylar “space blankets” are sold as a survivalist’s accessory, primarily due to their propensity for reflecting heat. They’re pretty cheap, and [HamJazz] has performed some experiments on their RF properties. Do they reflect radio waves as well as they reflect heat? As it turns out, yes they do.

Any antenna system that’s more than a simple radiator relies on using conductive components as reflectors. These can either be antenna elements, or the surrounding ground acting as an approximation to a conductor. Radio amateurs will often use wires laid on the ground or buried within it to improve its RF conductivity, and it’s in this function that he’s using the Mylar sheet. Connection to the metalized layer is made with a magnet and some aluminium tape, and the sheet is strung up from a line at an angle. It’s a solution for higher frequencies only due to the restricted size of the thing, but it’s certainly interesting enough to merit further experimentation.

As you can see in the video below, his results are derived in a rough and ready manner with a field strength meter. But they certainly show a much stronger field on one side resulting from the Mylar, and also in an antenna that tunes well. We would be interested to conduct a received signal strength test over a much greater distance rather than a high-level field strength test so close to the antenna, but it’s interesting to have a use for a space blanket that’s more than just keeping the sun away from your tent at a hacker camp. Perhaps it could even form a parabolic antenna.

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