Installing solar power at a home is a great way to reduce electricity bills, especially as the cost of solar panels and their associated electronics continue to plummet. Not every utility allows selling solar back to the grid, though, so if you’re like [Rogan] who lives in South Africa you’ll need to come up with some clever tricks to use the solar energy each day while it’s available to keep from wasting any. He’s devised this system for his water heater that takes care of some of this excess incoming energy.
A normal water heater, at least one based on electric resistive heaters, attempts to maintain a small range of temperatures within the insulated tank. If the temperature drops due to use or loss to the environment, the heaters turn on to bring the temperature back up. This automation system does essentially the same thing, but allows a much wider range of temperatures depending on the time of day. Essentially, it allows the water heater to get much hotter during times when solar energy is available, and lets it drop to lower values before running the heater on utility electricity during times when it isn’t. Using a combination ESP32 and ATtiny to both control the heater and report its temperature, all that’s left is to program Home Assistant to get the new system to interact with the solar system’s battery charge state and available incoming solar energy.
While it’s an elegantly simple system that also affords ample hot water for morning showers, large efficiency gains like this can be low-hanging fruit to even more home energy savings than solar alone provides on paper. Effectively the water heater becomes another type of battery in [Rogan]’s home, capable of storing energy at least for the day in the form of hot water. There are a few other ways of storing excess renewable energy as well, although they might require more resources than are typically available at home.
We’ve covered [mitxela] in the past and if you know him, you’ll likely know him for putting the micro in microelectronics. This year, he’s at it again with his LED Industrial Piercing.
Inspired by the absolutely tiny 0402 LEDs and industrial piercings, [mitxela] started thinking of a way to construct the 5cm long device. He found some normal LED earrings to steal the battery compartment from. Then, with a tick needle and some more steel, he created a new industrial earring with some holes.
Of course, no [mitxela] project is complete without comically tiny microsoldering and this project makes the VQFN ATTiny he used look large. He puts his PCB suppliers to the test with a merely 1mm wide flex PCB for the LEDs to be mounted on. Finally, he combines the flex PCB, the earring and some epoxy to create yet another piece of LED jewelry.
[Trent M. Wyatt]’s CPUVolt library provides a fast way to measure voltage using no external components, and no I/O pin. It only applies to certain microcontrollers, but he provides example Arduino code showing how handy this can be for battery-powered projects.
The classical way to measure a system’s voltage is to connect one of your MCU’s ADC pins to a voltage divider made from a couple resistors. A simple calculation yields a reading of the system’s voltage, but this approach has two disadvantages: one is that it constantly consumes power, and the other is that it ties up a pin that you might want to use for something else.
There are ways to mitigate these issues, but it would be best to avoid them entirely. Microchip application note 2447 describes a method of doing exactly that, and that’s precisely what [Trent]’s Arduino library implements.
What happens in this method is one selects Vbg (a fixed internal voltage reference that is temperature-independent) as Vin, and selects Vcc as the ADC’s voltage reference. This is essentially backwards from how the ADC is normally used, but it requires no external hookup and is only a bit of calculation away from determining Vcc in millivolts. There is some non-linearity in the results, but for the purposes of measuring battery power in a system or deciding when to send a “low battery” signal, it’s an attractive solution.
Being an Arduino library, CPUVolt makes this idea very easy to use, but the concept and method is actually something we have seen before. If you’re interested in the low-level details, then check out our earlier coverage which goes into some detail on exactly what is going on, using an ATtiny84.
Many readers will be familiar with Microchip’s ATtiny85, which has been a popular choice for DIY projects in the past for its low price and (for the time) small size. But those looking for a more modern and capable 8-bit chip may find the ATtiny1616-MNR of interest. It offers expanded flash storage, more GPIO, and ditches SPI programming in favor of UPDI — a protocol that can be done using nothing more than an USB-UART converter and a resistor.
The board contains an array of 6 by 7 LEDs in a charlieplexed configuration, a large piezo buzzer, two push buttons, an on/off switch, and a CR2032 battery holder to keep it on without the need for a cable. The kit looks gorgeous in its white-on-black theme with gold plated contacts and can be had for $20 on Tindie at the time of writing.
The ATtiny1616 itself runs at up to 20 MHz and has 17 GPIO pins, 16 KiB of flash storage, 2 KiB of RAM, and 256 bytes of EEPROM for configuration — making it roughly on par with the original Arduino Uno.
The course that goes hand-in-hand with the ACK1 is all about the features of the ATtiny1616, from the basics of using the programmer to reading the buttons, using timers, driving the charlieplexed LEDs, storing data in the EEPROM and much more. Though it does not cover the basics of C, the course is free, and even licensed MIT, so that anyone can share it and improve upon it.
The ThinkPad 701 is an iconic laptop series from the mid-90s and is still highly sought after today because of its famous butterfly keybaord. The laptop itself is tiny even by the standards of the time, so in order to fit a full-size keyboard IBM devised a mechanism where the keyboard splits and slides over itself to hide away as the screen is closed. But, like most 30-year-old laptops, the original batteries for these computers are well past their prime. [polymatt] takes us through all of the steps needed in order to recreate a battery from this era down to the last detail.
He starts by disassembling an old battery with extensive damage from the old, leaky batteries. The first part of the recreation is to measure the battery casing so a new one can be modeled and printed. The control boards for the batteries of these computers were not too sophisticated, so [polymatt] is able to use a logic analyzer with a working unit to duplicate its behavior on an ATtiny microcontroller. With that out of the way, a new PCB is created to host the cloned chip and a new battery pack, made out of 9 NiMH cells is put together.
[polymatt] wanted this build to be as authentic as possible, so he even goes as far as replicating the label on the underside of the battery. With everything put together he has a faithful recreation of this decades-old battery for a famous retro laptop. ThinkPads are popular laptops in general, too, due to their fairly high build quality (at least for their enterprise lineups) and comprehensive driver support especially for Linux and other open-source software projects like coreboot and libreboot.
A few months ago, a scandal erupted in the chess world which led to some pretty wild speculation around a specific chess player. We won’t go into any of the details except to say that there is virtually no physical evidence of any method this player allegedly used to cheat in a specific in-person chess match. But [Teddy Warner] and partner [Jack Hollingsworth] were interested in at least providing a proof-of-concept for how this cheating could have been done, though, and came up with this device which signals a chess player through a shoe.
The compact device is small enough to fit in the sole of one of the player’s shoes, and is powered by an ATtiny412 microcontroller paired with a HC-06 Bluetooth module. The electronics are fitted into a 3D printed case along with a small battery which can then be placed into the sole of a shoe, allowing the wearer to feel the vibrations from a small offset-weight motor. With a second person behind a laptop and armed with a chess engine, the opponent’s moves can be fed into the computer and the appropriate response telegraphed through the shoe to the player.
While [Teddy] and [Jack] considers the prototype a success in demonstrating the ease at which a device like this could be used, and have made everything related to this build open source, this iteration did have a number of issues including that the motor buzzing was noticeable during play, and that his chess engine made some bizarre choices in the end game. It also requires the complicity of a second person, which is something this other chess cheating machine does away with. They also note that it’s unlikely that any chess players at the highest levels use devices like these, and that other chess experts have found no evidence of any wrongdoing in this specific scandal.
The pendant has simple enough hardware — six LEDs arranged around the points of the star, all being driven by a small ATtiny3227 operating from a coin cell battery. This isn’t especially spectacular on it’s own, but this particular microcontroller is running an integer version of a custom-built Lisp interpreter called uLisp. The project’s creator did this simply because of the whimsy involved in running a high-level programming language on one of the smallest microcontrollers around that would actually support the limited functionality of this version of Lisp. This implementation does stretch the memory and processing capabilities of the microcontroller quite a bit, but with some concessions, it’s able to run everything without issue.