Your Battery Holder Is Also Your Power Switch With ToggleSlot

October 15, 2024 by Dave Rowntree 23 Comments

We really like PCB-level hacks, especially ones that show ingenuity in solving a real problem while being super cheap to implement. Hackaday.IO user [Steph] wanted a cheap way to switch a wearable on and off without having to keep popping out the battery, so they came up with a tweaked battery footprint, which is also a simple slide switch.

Most people making badges and wearables will follow the same well-trodden path of just yanking out the cell or placing some cheap switch down and swallowing the additional cost. For [Steph], the solution was obvious. By taking a standard surface-mount CR2032 button cell holder footprint, extending its courtyard vertically, and moving the negative pad up a smidge, the battery can be simply slid up to engage the pad and slid down to disengage and shut off the juice. The spring section of the positive terminal keeps enough pressure on the battery to prevent it from sliding out, but if you are worried, you can always add a dummy pad at the bottom, as well as a little solder bump to add a bit more security.

Now, why didn’t we think of this before? The KiCad footprint file can be downloaded from the project GitHub page, imported into your project and used straight away.

Many of our gadgets are powered by CR2032 cells—so many so that eliminating the need for them leads to interesting projects, like this sweet USB-powered CR2032 eliminator. But how far can you push the humble cell? Well, we held a contest a few years ago to find out!

Three different views of a tiny games console with a screen and a single button. It's assembled in the first picture, and the guts are shown in the second two pictures.

2024 Tiny Games Contest: Salsa One Handheld Requires No PCB

August 16, 2024 by Kristina Panos 10 Comments

If you’re thinking about building a single tiny game or even a platform, you might be tempted to use a single button for everything. Such is the case with [Alex]’s Salsa ONE minimalist game console, which is inspired by both the Arduboy and the ergonomics of the SanDisk Sansa music player.

With Salsa ONE, [Alex] aimed to make something that is both simple and challenging. The result is something that, awesomely enough, doesn’t need a PCB, and can be comfortably controlled with just one thumb. There isn’t much to this thing, which is essentially an RP2040, an OLED, a vibration motor, a buzzer, a button, and a CR2032 coin cell. [Alex] chose to program Salsa ONE in MicroPython. Be sure to check it out in action in the brief demo after the break.

Have you got an idea for a tiny game? Don’t hesitate to enter the 2024 Tiny Games Contest! You have until September 10th, so head on over to Hackaday.io and get started today.

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ATtiny85 Snake Game Is A Circuit Sandwich

March 26, 2022 by Kristina Panos 3 Comments

If there’s any looming, unwritten rule of learning a programming language, it states that one must break in the syntax by printing Hello, World! in some form or another. If any such rule exists for game programming on a new microcontroller, then it is certainly that thou shalt implement Snake.

This is [__cultsauce__]’s first foray away from Arduinoville, and although they did use one to program the ATtiny85, they learned a lot along the way.

It doesn’t take much to conjure Snake with an ’85 — mostly you need a screen to play it on (an OLED in this case), some buttons to direct the snake toward the food dot, a handful of passives, and a power source.

[__cultsauce__] started by programming the microcontroller and then tested everything on a breadboard, both of which are admirable actions. Then it was time to make this plywood and cork sandwich, which gives the point-to-point solder joints some breathing room and keeps them from getting crushed. Be sure to check it out in action after the break, and grab the files from GitHub if you want to charm your own ‘tiny Snake.

There’s a ton you can do with this miniature microcontroller, and that includes machine learning.

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Coin Cell Eliminator Does More Than Save Batteries

February 23, 2022 by Lewin Day 32 Comments

Coin cells are useful things that allow us to run small electronic devices off a tiny power source. However, they don’t have a lot of capacity, and they can run out pretty quickly if you’re hitting them hard when developing a project. Thankfully, [bobricius] has just the tool to help.

The device is simple – it’s a PCB sized just so to fit into a slot for a CR2016 or CR2032 coin cell. The standard board fits a CR2016 slot thanks to the thickness of the PCB, and a shim PCB can be used to allow the device to be used in a CR2032-sized slot instead.

It’s powered via a Micro USB connector, and has a small regulator on board to step down the 5 V supply to the requisite 3 V expected from a typical coin cell. [bobricius] also gave the device a neat additional feature – a pair of pads for easy attachment of multimeter current probes. Simply open the jumper on the board, hook up a pair of leads, and it’s easy to measure the current being drawn from the ersatz coin cell.

If you’re regularly developing low-power devices that use coin cells, this tool is one that could save a lot of mucking about in the lab. [bobricius] has them available on Tindie for those eager to get their hands on one. We’ve seen similar designs before too, albeit pursued in a different way!

Weather Station Dumps CR2032 Cells, Gains 18650

December 16, 2021 by Tom Nardi 34 Comments

Despite the fact that we’re rapidly approaching the year 2022, there are still an incredible number of gadgets out there that you’re expected to power with disposable batteries. Sure you can buy rechargeable stand-ins that come in the various shapes and sizes of the traditional alkaline cells, but that’s a stopgap at best. For some, if a new gadget doesn’t feature an internal Li-ion battery and standardized USB charging, it’s a non-starter.

[Danilo Larizza] is one of those people. Bothered by the fact that his Oregon Scientific weather station required a pair of CR2032 coin cells, he set out to replace them with an integrated rechargeable solution. The conversion ending up being easier to implement than he initially expected, and by his calculations, his solution should keep the unit up and running for nearly 40 days before needing to be topped off with a standard USB charger.

The first step was determining how much power it actually took to run the weather station. Although the two CR2032 cells were wired in series, and therefore providing a nominal 6 V, he determined through experimentation with a bench power supply that it would run on as little as 3.2 volts. This coincides nicely with the voltage range for a single 18650 cell, and meant he didn’t need to add a boost converter into the mix. He notes the weather station does flash a “Low Battery” warning most of the time now, but that seems a fair price to pay.

Confident in the knowledge that the weather station could happily run with an 18650 cell connected in place of the original CR2032s, all [Danilo] needed to do was figure out a way to charge the battery up from time to time. To that end, he reached for a common TP4056 module. This handy little board is a great match for 18650 cells, and is so cheap that there’s really no excuse not to have a few of them kicking around your parts bin. You never know when you might need to teach an old gadget new tricks.

A CR2032 Battery Eliminator

April 24, 2020 by Al Williams 26 Comments

Back when batteries were expensive and low-capacity, it was common to buy a “battery eliminator” that could substitute for common battery configurations. [David Watts] must remember those, because he decided to make an eliminator for all the CR2032 battery-driven gear he has. He got some brass blanks about the size of the battery, and you can see the results on the video below.

His first attempt seemed to work fairly well, a sandwich of two brass disks, each with a Velcro spacer and wires soldered on to connect to a power supply. The fake battery looks as though it might be a little thick, but it did work once the battery holder was persuaded to accept it.

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Tiny Two-Digit Thermometer Has Long Battery Life

May 29, 2019 by Donald Papp 20 Comments

Like most of his work, this tiny two-digit thermometer shows that [David Johnson-Davies] has a knack for projects that make efficient use of hardware. No pin is left unused between the DS18B20 temperature sensor, the surface mount seven-segment LED displays, and the ATtiny84 driving it all. With the temperature flashing every 24 seconds and the unit spending the rest of the time in a deep sleep, a good CR2032 coin cell should power the device for nearly a year. The board itself measures only about an inch square.

You may think that a display that flashes only once every 24 seconds might be difficult to actually read in practice, and you’d be right. [David] found that it was indeed impractical to watch the display, waiting an unknown amount of time to read some briefly-flashed surprise numbers. To solve this problem, the decimal points flash shortly before the temperature appears. This countdown alerts the viewer to an incoming display, at the cost of a virtually negligible increase to the current consumption.

[David]’s project write-up explains how everything functions. He also steps through the different parts of the source code to explain how everything works, including the low power mode. The GitHub repository holds all the source files, and the board can also be ordered direct from OSH Park via their handy shared projects feature.

Low power consumption adds complexity to projects, but the payoffs can easily be worth the time spent implementing them. We covered a detailed look into low power WiFi microcontrollers that is still relevant, and projects like this weather station demonstrate practical low power design work.