PTPM Energy Scavenger Aims for Maintenance-Free Sensor Nodes

[Mile]’s PTPM Energy Scavenger takes the scavenging idea seriously and is designed to gather not only solar power but also energy from temperature differentials, vibrations, and magnetic induction. The idea is to make wireless sensor nodes that can be self-powered and require minimal maintenance. There’s more to the idea than simply doing away with batteries; if the devices are rugged and don’t need maintenance, they can be installed in locations that would otherwise be impractical or awkward. [Mile] says that goal is to reduce the most costly part of any supply chain: human labor.

The prototype is working well with solar energy and supercapacitors for energy storage, but [Mile] sees potential in harvesting other sources, such as piezoelectric energy by mounting the units to active machinery. With a selectable output voltage, optional battery for longer-term storage, and a reference design complete with enclosure, the PPTM Energy Scavenger aims to provide a robust power solution for wireless sensor platforms.

Amiga Repairs Put One Tough Little Machine Back in Service

Returning a piece of retro hardware to factory condition is generally a labor of love for the restorationist. A repair, on the other hand, is more about getting a piece of equipment back into service. But the line between repair and restoration is sometimes a fine one, with the goals of one bleeding over into the other, like in this effort to save an otherwise like-new Amiga 2000 with a leaky backup battery.

Having previously effected emergency repairs to staunch the flow of electrolyte from the old batteries and prevent further damage, [Retromat] entered the restoration phase of the project. The creeping ooze claimed several caps and the CPU socket as it spread across the PCB, but the main damage was to the solder resist film itself. In the video below you can clearly see flaky, bubbly areas in the mask where the schmoo did its damage.

Using a fiberglass eraser, some isopropyl alcohol, and far more patience than we have, [Retromat] was able to remove the damaged resist to reveal the true extent of the damage below. Thankfully, most of the traces were still intact; only a pair of lines under the CPU socket peeled off as he was removing it. After replacing them with fine pieces of wire, replacing the corroded caps and socket, and adding a coin-cell battery holder to replace the old battery, the exposed traces were coated with a varnish to protect them and the machine was almost as good as new.

Amigas were great machines in their day and launched more than one business. They’ve proved their staying power too, some even in mission-critical roles.

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Micro-Organisms Give Up the Volts in this Biological Battery

Battery cells work by chemical reactions, and the fascinating Hybrid Microbial Fuel Cell design by [Josh Starnes] is no different. True, batteries don’t normally contain life, but the process coughs up useful electrons all the same; 1.7 V per cell in [Josh]’s design, to be precise. His proof of concept consists of eight cells in parallel, enough to give his cell phone a charge via a DC-DC boost converter. He says it’s not known how long this can be expected to last before the voltage drops to an unusable level, but it works!

Eight-cell, 3D printed proof of concept.

There are two complementary sides to each cell in [Josh]’s design. On the cathode side are phytoplankton; green micro algae that absorb carbon dioxide and sunlight. On the anode side are bacteria that break organic material (like food waste) into nitrates, and expel carbon dioxide. Version 2 of the design will incorporate a semi-permeable membrane between the cells that would allow oxygen and carbon dioxide to be exchanged while keeping the populations of micro-organisms separate; this would make the biological processes more complementary.

A battery consisting of 24 cells and a plumbing system to cycle and care for the algae and bacteria is the ultimate goal, and we hope [Josh] can get closer to that now that his project won a $1000 cash prize as one of the twenty finalists in the Power Harvesting Challenge portion of the Hackaday Prize. (Next up is the Human Computer Interface Challenge, just so you know.)

Custom Circuit Makes for Better Battery Level Display

Isn’t it always the way? There’s a circuit right out of the textbooks, or even a chip designed to do exactly what you want — almost exactly. It’s 80% perfect for your application, and rather than accept that 20%, you decide to start from scratch and design your own solution.

That’s the position [Great Scott!] found himself in with this custom LED battery level indicator. As the video below unfolds we learn that he didn’t start exactly from scratch, though. His first pass was the entirely sensible use of the LM3914 10-LED bar graph driver chip, a device that’s been running VU meters and the like for the better part of four decades. With an internal ladder of comparators and 1-kilohm resistors, the chip lights up the 10 LEDs according to an input voltage relative to an upper and lower limit set by external resistors. Unfortunately, the fixed internal resistors make that a linear scale, which does not match the discharge curve of the battery pack he’s monitoring. So, taking design elements from the LM3914 datasheet, [Great Scott!] rolled his own six-LED display from LM324 quad-op amps. Rather than a fixed resistance for each stage, trimmers let him tweak the curve to match the battery, and now he knows the remaining battery life with greater confidence.

Perhaps the 18650 battery pack [Great Scott!] is building is for the e-bike he has been working on lately. If it is, we’re glad to see that he spot-welded the terminals, unlike a recent e-bike battery pack build that may have some problems down the road.

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Amiga 2000 Emergency Repair

Big companies spend small fortunes on making sure their computers stay running and that they can be repaired quickly in an emergency. You wouldn’t expect an emergency repair on an Amiga 2000, though. [RETR-O-MAT] bought an Amiga 2000 that did boot, but was known to have a leaky battery on the motherboard. He wanted to rush to replace the battery before the leakage caused serious damage. You can see all this in the video below.

The computer looked lightly used over its 32-year lifespan, even when the case came off. The battery corrosion was evident, though. Even the bolt holding down the motherboard was clearly corroded from the leaking battery, causing it to be very difficult to remove.

The battery leakage also made unsoldering the battery a challenge. Several chips and sockets — including the CPU — were affected, so they had to come out. You can see a nice demonstration of the “old screwdriver trick” which might be eye-opening if you’ve only worked with SMD chips.

Even if you don’t care much about the Amiga 2000, it is interesting to see inside an old computer like this and note the differences — and similarities — to modern designs. The video is as much a tear down as it is a repair story. It also might be useful if you ever face having to tear out a leaky battery on any piece of gear. Continue reading “Amiga 2000 Emergency Repair”

This Smart Pill Uses A Stomach Acid Battery

[Curt White] is working on a smart pill whose copper-zinc battery will use his own stomach acid as the electrolyte. It’s not that unusual of an idea, MIT tested a similar approach in a pig. It’s also better than using lithium ion batteries, something we covered in this PSA.

Smartpill circuit diagram
Smartpill circuit diagram

His starting point is a small, hacked activity tracker with its Nordic nRF51822 ARM Cortex-M0 and Bluetooth LE SoC. Most everything else is removed. The battery electrodes are sewn onto a plastic mesh cut to the activity tracker’s dimensions. Three coin type super capacitors and a boost converter sit between the battery and the SoC.

He uses the Bluetooth LE for communication, sort of. BLE devices constantly transmit information about themselves and it’s this which you see when scanning for available devices. Included in that transmission is a UUID (Universally Unique Identifier) and a name (e.g. “smartpillxyz”). He has the pill transmit data by putting it in that name. This saves power by minimizing the time which the pill’s Bluetooth radio is turned on. The smartphone app extracts the data from these transmissions without ever connecting.

His goal is to monitor the voltage and the maximum current. This will tell him if his stomach acid battery works and what can be powered by it. First tests will use regurgitated gastric fluid and then later he’ll swallow the pill himself. As he puts it, why not, “people swallow and pass all kinds of weird stuff without a problem.” Thay may sound cavalier but judging by his page, he’s doing his homework.

An E-Bike Battery Pack Without Spot Welding

In somewhat of a departure from their normal fare of heavy metal mods, [Make It Extreme] is working on a battery pack for an e-bike that has some interesting design features.

The guts of the pack are pretty much what you’d expect – recovered 18650 lithium-ion cells. They don’t go into details, but we assume the 52 cells were tested and any duds rejected. The arrangement is 13S4P, and the cells are held in place with laser-cut acrylic frames. Rather than spot weld the terminals, [Make It Extreme] used a series of strategically positioned slots to make contacts from folded bits of nickel strip. Solid contact is maintained by cap screws passing between the upper and lower contact frames. A forest of wires connects each cell to one of four BMS boards, and the whole thing is wrapped in a snappy acrylic frame. The build and a simple test are in the video below.

While we like the simplicity of a weld-less design, we wonder how the pack will stand up to vibration with just friction holding the cells in contact. Given their previous electric transportation builds, like this off-road hoverbike, we expect the pack will be put to the test soon, and in extreme fashion.

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