A Solar Freakin’ Walkway

Looking to add a little pizzazz to your back garden? Are those strings of lights hung in the trees looking a little dated? Why not try lighting your garden path with DIY solar-powered pavers?

If [jfarro]’s project looks like a miniature version of the much-touted solar freakin’ roadways concept, rest assured that there are huge differences. For one, these lighted pavers actually work — trust me on this; I live not far from the demo site for the Solar Roadways and the degree to which it underwhelms cannot be overstated. Granted, a garden path is a lot simpler to engineer than a road, but many of the challenges remain.

Using recycled glass blocks that are usually reserved for walls and windows, [jfarro] figured out how to attach Neopixel rings to the underside and waterproof them with a silicone conformal coating. The 12 lighted pavers he built draw considerable current, so a 45-watt solar array with charge controller and battery were installed to power the pavers. An Arduino and a motion sensor control the light show when someone approaches; more complicated programs are planned.

Hats off the [jfarro] for taking on a project like this. We don’t often see builds where electrical engineering meets civil engineering, and even on a small scale, dealing with dirt, stone, and water presents quite a few challenges. Here’s hoping his project lasts longer than the Solar Roadways project did.

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Innovating A Backyard Solar Battery System

Ever on the lookout for creative applications for tech, [Andres Leon] built a solar powered battery system to keep his Christmas lights shining. It worked, but — pushing for innovation — it is now capable of so much more.

The shorthand of this system is two, 100 amp-hour, deep-cycle AGM batteries charged by four, 100 W solar panels mounted on an adjustable angle wood frame. Once back at the drawing board, however, [Leon] wanted to be able track real-time statistics of power collected, stored and discharged, and the ability to control it remotely. So, he introduced a Raspberry Pi running Raspbian Jessie Lite that publishes all the collected data to Home Assistant to be accessed and enable control of the system from the convenience of his smartphone. A pair of Arduino Deuemilanoves reporting to the Pi control a solid state relay powering a 12 V, 800 W DC-to-AC inverter and monitor a linear current sensor — although the latter still needs some tinkering. A in-depth video tour of the system follows after the break!

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A Poor-Man’s Laser CNC Engraver

What do you get when you mix the disappointment that sometimes accompanies cheap Chinese electronics with the childhood fascination of torturing insects with a magnifying glass on a sunny day? You get a solar-powered CNC etcher, that’s what.

We all remember the days of focussing the sun on a hapless insect, or perhaps less sadistically on a green plastic army man or just a hunk of dry wood. The wonder that accompanied that intense white spot instantly charring the wood and releasing wisps of smoke stayed with you forever, as seemingly did the green spots in your vision. [drum303] remembered those days and used them to assuage his buyer’s remorse when the laser module on his brand new CNC engraver crapped out after the first 10 minutes. A cheap magnifying glass mounted to the laser holder and a sunny day, and he don’t need no stinkin’ lasers! The speed needs to be set to a super slow — 100mm per minute — and there’s the problem of tracking the sun, but the results are far finer than any of our childhood solar-artistic attempts ever were.

Do we have the makings of a possible performance art piece here? A large outdoor gantry with a big Fresnel lens that could etch a design onto a large piece of plywood would be a pretty boss beachside attraction. Of course, you’d need a simple solar tracker to keep things in focus.

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Finally, A Calculator For The Atomic Age!

In the 1950s, a nuclear-powered future seemed a certainty. The public had not been made aware of the dangers posed by radioactive material, any large-scale accidents involving nuclear reactors had either been hushed up or were yet to happen, and industry and governments were anxious to provide good PR to further their aims. Our parents and grandparents were thus promised a future involving free energy from nuclear reactors in all sorts of everyday situations.

With the benefit of hindsight, we of course know how the story turned out. Windscale, Three Mile Island, Chernobyl, and Fukushima, and we’re still waiting for our atomic automobiles.

If you have a hankering for nuclear-powered domestic appliances though, all is not lost. [GH] is leading the charge towards a future of atomic energy, with a nuclear-powered calculator. It’s not quite what was promised in the ’50s, but it is nevertheless a genuine appliance for the Atomic Age. At its heart is not a 1950s-style fission reactor though, but a tritium tube. Beta particles from the tritium’s decay excite a phosphor coating on the tube’s inside wall, producing a small amount of light. This light is harvested with a solar cell, and the resulting electrical energy is stored in an electrolytic capacitor. The cell has an open-circuit voltage of 1.8 V, and the 100 μF capacitor in question stores a relatively tiny 162 μJ. From this source, a dollar store calculator can operate for about 30 sec, so there should be no hanging about with your mathematics.

We’ve brought you a tritium battery before, albeit a slightly larger one. And should you need the comforting glow of a tritium tube but not the radiation risk, how about this LED-based substitute?

Energy Harvesting Wristwatch Uses a Versatile Photodiode

There’s some interesting technology bundled into this energy harvesting wristwatch. While energy harvesting timepieces (called automatic watches) have been around for nearly 240 years, [bobricius] has used parts and methods that are more easily transferable to other projects.

Unlike early mechanical systems, this design uses the versatile BPW34 PIN photodiode (PDF warning). PIN photodiodes differ from ordinary PN diodes in that there’s a layer of undoped ‘intrinsic’ silicon separating the P and N doped layers. This reduces the utility of the diode as a rectifier, while allowing for higher quantum efficiency and switching speed.

They are typically used in the telecommunications industry, but have a number of interesting ‘off label’ applications. For example, the BPW34 can be used as a solid-state particle detector (although for detecting alpha particles you’re better off with something in a TO-5 package such as the Hamamatsu S1223-01). The fast response speed means you can send data with lasers or ambient light at high frequencies – a fun use for an LED lighting system or scrap DVD-RW laser.

Some common solar panels are essentially large PIN photodiodes. These are the brownish panels that you’ll find in a solar-powered calculator, or one of those eternally waving golden plastic neko shrines. They specifically offer excellent low-light performance, which is the basis of the energy harvesting used in this project.

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A Solar-Powered Headset From Recycled Parts

Solar power has surged ahead in recent years, and access for the individual has grown accordingly. Not waiting around for a commercial alternative, Instructables user [taifur] has gone ahead and built himself a solar-powered Bluetooth headset.

Made almost completely of recycled components — reducing e-waste helps us all — only the 1 W flexible solar panel, voltage regulator, and the RN-52 Bluetooth module were purchased for this project. The base of the headset has been converted from [taifur]’s old wired one, meanwhile a salvaged boost converter, and charge controller — for a lithium-ion battery — form the power circuit. An Apple button makes an appearance alongside a control panel for a portable DVD player (of all things), and an MP4 player’s battery. Some careful recovery and reconfiguration work done, reassembly with a little assistance from the handyman’s secret weapon — duct tape — and gobs of hot glue bore a wireless fruit ready to receive the sun’s bounty.

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Solar Controller Reverse Engineered In Both Directions

[Jared Sanson] has a solar power setup on his beach house, consisting of 6 panels and a 24V battery bank, supplied by Outback Inc. Their chargers and inverters pair over a seemingly proprietary connection with a controller known as the MATE. The MATE has a standard serial output which gives some details about the operation, but [Jared] wasn’t getting the detailed information they could get from the controller’s screen. This meant it was time to reverse engineer the proprietary connection instead, which [Jared] calls MateNET.

The controller interfaces with the chargers over a Cat5 cable. [Jared] initially suspected RS-485, but it turned out to be regular serial at 0-24V logic levels, at 9600 baud, 9n1. To figure out the pinout, [Jared] went through the MATE circuitry with a fine-toothed comb, discovering an ATMEGA32. Since both the MATE’s user output & its connection to the other equipment are both serial, a logic mux is used to split the ATMEGA32’s single UART between the two serial connections. With the physical layer sorted, it was time to figure out how the protocol worked.

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