Tiny PIC Clock is Not a Tiny Bomb

It’s been a few weeks since the incident where Ahmed Mohamed, a student, had one of his inventions mistaken for a bomb by his school and the police, despite the device clearly being a clock. We asked for submissions of all of your clock builds to show our support for Ahmed, and the latest one is the tiniest yet but still has all of the features of a full-sized clock (none of which is explosions).

[Markus]’s tiny clock uses a PIC24 which is a small yet powerful chip. The timekeeping is done on an RTCC peripheral, and the clock’s seven segment displays are temporarily lit when the user presses a button. Since the LEDs aren’t on all the time, and the PIC only consumes a few microamps on standby, the clock can go for years on a single charge of the small lithium-ion battery in the back. There’s also a phototransistor which dims the display in the dark, and a white LED which could be used as a small flashlight in a pinch. If these features and the build technique look familiar it’s because of [Markus’] tiny MSP430 clock which he was showing around last year.

Both of his tiny clocks are quite impressive for their size, features, and power consumption. Some of the other clocks we’ve featured recently include robot clocks, clocks for social good, and clocks that are not just clocks (but still won’t explode). We’re suckers for a good clock project here, so keep sending them in!

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ESP8266 WiFi Throwies

A few years ago, someone figured out you can take an LED, a coin cell battery, and a magnet, tape them together, and throw them on every conceivable metallic surface. This was the creation of LED throwies, and the world was much worse off for its invention.

With the ESP-8266 WiFi module, we have a tiny, tiny device with a WiFi radio, and just enough processing power to do something interesting. What does that mean? WiFi throwies.

[Andreas Reischle] stuffed an ESP-8266 WiFi module and a lithium cell inside a weatherproof controller loaded up with magnets. On its own, these wouldn’t do much, but with the right combination of software, this little magnetic box can serve as an access point, serving up small JavaScript games to anyone who connects.

The software is based on the NodeMCU firmware and features a web server and a DNS server. The utility of a web server is obvious, and the DNS server redirects all traffic to the device’s index.html file, where a menu of small JavaScript games are presented.

It’s much better than polluting the world with LEDs and lithium; this one has Hunt the Wumpus on it.

Thanks [Oliver] for the tip.

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Battery Basics – Choosing a Battery for Your Project

If choosing a rechargeable battery for your project intimidates you, [Afroman] has prepared a primer video that should put you at ease. In this tutorial for battery basics he not only walks you through a choice of 5 rechargeable chemistries and their respective tradeoffs, but gives a procedure that will allow you to navigate through the specs of real-world batteries for sale – something that can be the most intimidating part of the process.

You cannot learn everything about batteries in 9 minutes, but watching this should get you from zero to the important 80% of the way there. Even if your project does not give you the specs you need to begin buying, [Afroman] tells you what to measure and how to shop for it. In particular, the information he gives is framed in the context you care about, hopefully ensuring you are not waylaid by all the details that were safe to ignore. If this is not enough, [Afroman]’s prequel video on battery terminology has more detail.

Much like your high school English teacher told you, you need to know the rules before you can choose to break them. Many of battery absolute Dos or Don’ts are written for the manufacturer, who provides for the consumer, not the hacker. Hackaday has published hundreds of battery articles over the years; search our archives when you are ready for more.

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Programmable Lithium Charger Shield for Arduino

Surely you need yet another way to charge your lithium batteries—perhaps you can sate your desperation with this programmable multi (or single) cell lithium charger shield for the Arduino?! Okay, so you’re not hurting for another method of juicing up your batteries. If you’re a regular around these parts of the interwebs, you’ll recall the lithium charging guide and that rather incredible, near-encyclopedic rundown of both batteries and chargers, which likely kept your charging needs under control.

That said, this shield by Electro-Labs might be the perfect transition for the die-hard-‘duino fanatic looking to migrate to tougher projects. The build features an LCD and four-button interface to fiddle with settings, and is based around an LT1510 constant current/constant voltage charger IC. You can find the schematic, bill of materials, code, and PCB design on the Electro-Labs webpage, as well as a brief rundown explaining how the circuit works. Still want to add on the design? Throw in one of these Li-ion holders for quick battery swapping action.

[via Embedded Lab]

A Li-ion Battery Charging Guide

Although [pinomelean’s] Lithium-ion battery guide sounds like the topic is a bit specific, you’ll find a number of rechargeable battery basics discussed at length. Don’t know what a C-rate is? Pfffft. Roll up those sleeves and let’s dive into some theory.

As if you needed a reminder, many lithium battery types are prone to outbursts if mishandled: a proper charging technique is essential. [pinomelean] provides a detailed breakdown of the typical stages involved in a charge cycle and offers some tips on the advantages to lower voltage thresholds before turning his attention to the practical side: designing your own charger circuit from scratch.

The circuit itself is based around a handful of LM324 op-amps, creating a current and voltage-limited power supply. Voltage limits to 4.2V, and current is adjustable: from 160mA to 1600mA. This charger may take a few hours to juice up your batteries, but it does so safely, and [pinomelean’s] step-by-step description of the device helps illustrate exactly how the process works.

[Thanks mansalvo]

PSP Lithium Hack Could Be Called the Franken-Cell

You assume that you’ll be able to get parts forever… after all: The Internet. But what if you can’t justify paying the price for them? [Cristi C.] was in this situation, not wanting to fork over $30+ for a replacement PSP battery. The handheld gaming rig itself was just discontinued this year but supposedly the batteries have been out of production for some time. What you see above is the controller board from an original battery, with the cell from a camera battery.

The key is protection. The chemistry in Lithium cells of several types brings a working voltage of around 3.7V. Swapping the cells — even if they are different capacities — should work as protection circuits generally measure current, voltage, and sometimes temperature as they charge in order to know when the cell is full. With this in mind [Christi] cracked open a used Canon NB-6L type battery and grabbed the prismatic cell as a replacement for the pouch cell in the Sony S110 case (PDF). The Canon cell is enclosed in a metal case and is just a bit smaller than the pouch was. This means with careful work it fit back inside the original plastic enclosure.

On a somewhat related note, be careful when sourcing brand-x batteries. Some manufacturers implement checks for OEM equipment but there are ways around that.

An Obsessively Thorough Battery (and more) Showdown

There are a number of resources scattered across the Internet that provide detailed breakdowns of common products, such as batteries, but we haven’t seen anything quite as impressive as this site. It’s an overwhelming presentation of data that addresses batteries of all types, including 18650’s (and others close in size)26650’s, and more chargers than you can shake a LiPo at. It’s an amazing site with pictures of the product both assembled and disassembled, graphs for charge and discharge rates, comparisons for different chemistries, and even some thermal images to illustrate how the chargers deal with heat dissipation.

Check out the review for the SysMax Intellicharger i4 to see a typical example. If you make it to the bottom of that novel-length repository of information, you’ll see that each entry includes a link to the methodology used for testing these chargers.

But wait, there’s more! You can also find equally thorough reviews of flashlights, USB chargers, LED drivers, and a few miscellaneous overviews of the equipment used for these tests.

[Thanks TM]