Tiny Solar Energy Module (TSEM) Brings Big Performance

The Tiny Solar Energy Module (TSEM) by [Jasper Sikken] is not only physically tiny at one-inch square, but it is all about gathering tiny amounts of solar energy — amounts too small to be useful in a conventional sense — and getting meaningful work done, like charging a battery for later use. Elements that make this board easy to integrate into other projects include castellated vias, 1.8 V and 3.3 V regulated outputs that are active when the connected battery has a useful charge, and a low battery warning that informs the user of impending shutdown when the battery runs low. The two surface-mount solar cells included on the tiny board are capable of harvesting even indoor light, but the board also has connection points for using larger external solar cells if needed.

The board shows excellent workmanship and thoughtful features; it was one of the twenty Power Harvesting Challenge finalists chosen to head to the final round of The Hackaday Prize. The Hackaday Prize is still underway, with the Human-Computer Interface Challenge running until August 27th. That will be followed by the Musical Instrument Challenge before the finals spin up. If you haven’t started yet, there’s still time to make your mark. All you need is a documented idea, so start your entry today.

Charging USB-C Devices Off Of LiPo Battery Packs

When it was introduced in the late 90s, USB was the greatest achievement in all of computing. Gone were the PS/2 connectors for keyboards and mice, ADB ports, parallel ports, game ports, and serial ports. This was a Tower of Babel that would unite all ports under one standard universal bus.

Then more ports were introduced; micro, mini, that weird one that was a mini USB with more connectors off to the side. Then we started using phone chargers as power supplies. The Tower of Babel had crumbled. Now, though, there is a future. USB-C is everything stuffed into one port, and it can supply 100 Watts of power.

Delivering power over a USB-C connector is an interesting engineering challenge, and for his Hackaday Prize entry, [Chris Hamilton] is taking up the task. He’s building a USB-C battery charger, allowing him to charge standard R/C battery packs over USB.

There are two major components of the charger. The first, a Cypress CCG2 USB Power Delivery negotiator, handles all the logic of sending a command to the USB power supply and telling it to open up the pipes. It’s an off-the-shelf part and the implementation is well documented in app notes. The second major component is the battery management circuit built on a TI BQ40z60RHB. This includes the charger control logic and the ability to balance up to four cells. Battery connectors are XT-30, so all your drone battery packs can now be charged by a MacBook.

Ultra-Low Power, Energy Harvesting Battery Charger

This half-inch square ultra-low power energy harvesting LiPo cell charger by [Kris Winer] uses a low voltage solar panel to top up a small lithium-polymer cell, which together can be used as the sole power source for projects. It’s handy enough that [Kris] uses them for his own projects and offers them for sale to fellow hackers. It’s also his entry into the Power Harvesting Challenge of the Hackaday Prize.

The board is essentially a breakout board for the Texas Instrument BQ25504, configured to charge and maintain a single lithium-polymer cell. The BQ25504 is an integrated part that takes care of most of the heavy lifting and has nifty features like battery health monitoring and undervoltage protection. [Kris] has been using the board along with a small 2.2 Volt solar panel and a 150 mAh LiPo cell to power another project of his: the SensorTile environmental data logger.

It’s a practical and useful way to test things; he says that an average of 6 hours of direct sunlight daily is just enough to keep the 1.8 mA SensorTile running indefinitely. These are small amounts of power, to be sure, but it’s free and self-sustaining which is just what a remote sensing unit needs.

Battery-Powered Watering Timer Converted to Solar on the Cheap

Watering the garden or the lawn is one of those springtime chores that is way more appealing early in the season than later. As the growing season grinds along, a chore that seemed life-giving and satisfying becomes, well, just another chore, and plants often suffer for it.

Automating the watering task can be as simple as buying a little electronic timer valve that turns on the flow at the appointed times. [A1ronzo] converted his water hose timer to solar power. Most such timers are very similar, with a solenoid-operated pilot valve in line with the water supply and an electronic timer of some sort. The whole thing is quite capable of running on a pair of AA batteries, but rather than wasting money on new batteries several times a season, he slipped a LiPo pack and a charge controller into the battery case slot and connected a small solar panel to the top of the controller.

The LiPo is a nominal 3.7-volt pack, so he did a little testing to make sure the timer would be OK with the higher voltage. The solar panel sits on top of the case, and the whole thing should last for years. And bonus points for never having to replace a timer that you put away at the end of the season with batteries still in it, only to have them leak. Ask us how we know.

Like the best of hacks, this one is quick, easy and cheap — $15 in parts, aside from the timer. There are more complicated irrigation solutions, of course, one of which even won the Hackaday Prize once upon a time. But this one has us ordering parts to build our own right now.

Make Christmas Commercial Again with this Tiny TV Ornament

Readers of a certain age will remember a time when the Christmas season in the US officially kicked off after Thanksgiving. That was when advertisers began saturation bombing the communal mind with holiday-themed TV commercials night and day. Broadcast TV no longer holds sway like it did back then, and advertisers now start their onslaught in September, but you can put a little retro-commercialism back to Christmas with this 90s Christmas commercial-playing ornament for your tree.

The idea came to [SeanHodgins] after stumbling upon a collection of Christmas commercials from the 1990s on YouTube. With his content identified, he set about building a tree-worthy display from a Pi Zero W and a TFT LCD display. An audio amp and tiny speaker from an old tablet and a LiPo battery and charger form the guts of [Sean]’s TV, which were stuffed into a 3D-printed TV case, appropriately modeled after the TV from The Simpsons. The small fresnel lens that mimics the curved screens of yore is a nice touch. The software has some neat tricks, such as an HTTP server that accepts the slug of a YouTube video, fetches the MP4, and automatically plays it. We prefer our Christmas tree ornaments a little quieter, so a volume control would have been nice, but aside from that this looks like a ton of fun.

This isn’t [Sean]’s first foray into tricked-out ornaments, of course; readers might recall his IoT cheer-measuring Christmas ornaments from last season.

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Cheap RC Truck Mod Is Slightly Risky Fun

The world of RC can be neatly split into two separate groups: models and toys. The RC models are generally big, complex, and as you’d imagine, more expensive. On the other hand, the RC toys are cheap and readily available. While not as powerful or capable as their more expensive siblings, they can often be a lot of fun; especially since the lower costs means a crash doesn’t put too big of a ding into to your wallet.

With his latest mod, [PoppaFixIt] has attempted to bridge the gap between toy and model by sticking a considerably overpowered battery into a $10 RC truck from Amazon. He reports greatly improved performance from his hacked together truck, but anyone looking to replicate his work should understand the risks before attempting to hack up their own version.

The principle is pretty simple; the truck is designed to run on two AA batteries, providing 3 volts. But by swapping the AAs out for a 3.7 volt 1S LiPo of the type that’s used in small airplanes and quadcopters, you can get an instant boost in power. As a happy side effect, the LiPo batteries are also rechargeable and fairly cheap, so you won’t have to keep burning through alkaline AAs.


The mod itself is a basic job that only requires a few bucks in parts, and for which [PoppaFixIt] has helpfully provided Amazon links. Essentially you just crack open the truck, solder a JST connector pigtail to the positive and negative traces on the PCB, and then pop a hole in the roof to run the new battery wires out.

Right about now the RC purists are probably screaming obscenities at their displays, and not without reason. As fun as these supercharged little trucks are to drive, there are a number of real issues here which need to be mentioned.

First, while the motor will probably be alright with a bit higher voltage running through them, the gears won’t be liking it one bit. In fact, [PoppaFixIt] even mentions they shredded a few gears when they tried to take one off-road. The second issue is that since these vehicles were not designed with LiPo batteries in mind, there’s no low voltage cutoff to prevent over discharge. If you aren’t careful, a setup like this will cook those cute little batteries in short order. But hey, at least it’s all cheap.

If you are more interested in control than power, you may want to check out the previous hacks we’ve featured. Seems like these little RC trucks are the platform of choice for hackers who want to get stuff moving on the cheap.

The Science Behind Lithium Cell Characteristics and Safety

To describe the constraints on developing consumer battery technology as ‘challenging’ is an enormous understatement. The ideal rechargeable battery has conflicting properties – it has to store large amounts of energy, safely release or absorb large amounts of it on demand, and must be unable to release that energy upon failure. It also has to be cheap, nontoxic, lightweight, and scalable.

As a result, consumer battery technologies represent a compromise between competing goals. Modern rechargeable lithium batteries are no exception, although overall they are a marvel of engineering. Mobile technology would not be anywhere near as good as it is today without them. We’re not saying you cannot have cellphones based on lead-acid batteries (in fact the Motorola 2600 ‘Bag Phone’ was one), but you had better have large pockets. Also a stout belt or… some type of harness? It turns out lead is heavy.

The Motorola 2600 ‘bag phone’, with a lead-acid battery. Image CC-BY-SA 3.0 source: Trent021

Rechargeable lithium cells have evolved tremendously over the years since their commercial release in 1991. Early on in their development, small grains plated with lithium metal were used, which had several disadvantages including loss of cell capacity over time, internal short circuits, and fairly high levels of heat generation. To solve these problems, there were two main approaches: the use of polymer electrolytes, and the use of graphite electrodes to contain the lithium ions rather than use lithium metal. From these two approaches, lithium-ion (Li-ion) and lithium-polymer (Li-Po) cells were developed (Vincent, 2009, p. 163). Since then, many different chemistries have been developed.

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