hand warmer

4 Articles

Teardown: Go Warmer USB Rechargeable Hand Heater

March 9, 2021 by 31 Comments

Under normal circumstances, if an electronic gadget in your pocket suddenly became hot to the touch, it would be cause for alarm. But not so with the Go Warmer. This lozenge shaped device is not only a USB power bank that can keep your mobile devices topped up, but is also doubles as a miniature heater that the manufacturer claims can bring its surface temperature up to 48 °C (120 °F) for several hours. You can hold in in your hand, put it in your pocket, maybe even sit on it if you’re particularly daring. The possibilities are endless, at least until the 4,000 mAh battery runs down.

For $14.99 USD, the Go Warmer certainly isn’t much of a deal when compared to other battery packs. Even if it does come with a swanky velveteen carrying pouch. But is it a good deal for one that can heat itself up without exploding? Let’s crack this metallic egg and find out.

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Cooking Eggs With Hand Warmers

February 4, 2021 by 27 Comments

Handwarmers are great to keep your fingers functional in icy weather, but can they do more? [Greg] wondered if they could be put to good use cooking an egg, and got down to work.

The handwarmers in question are the HotHands brand, based on an iron chemistry. The warmers create their heat from the exothermic reaction between iron and oxygen that creates rust. Thus, these handwarmers need plenty of airflow to heat up. To enable this, [Greg] 3D printed a small crate with plenty of vents, into which he stacked six hand warmer sachets. An egg was nestled in the center – a perfect choice as it can be cooked in its own packaging. The pile reached temperatures of 160 F and was able to maintain that level for an hour, important as egg proteins tend to start coagulating and denaturing around 150 F. Once removed, [Greg] hoped to find a solid egg, but instead was rewarded with a somewhat gooey, semi-solid result instead. Regardless, the egg had reached an elevated temperature and shown some signs of cooking, and as [Greg] appears to be still putting out videos, we’ll assume he hasn’t yet died of salmonella.

We’d love to see this turn into an engineering competition, though, with prizes for the best cooked egg with the least amount of handwarmers. We’ve featured other egg cooking apparatus before, too. Video after the break.

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How Not To Build A CPU Hand Warmer

November 12, 2016 by 50 Comments

Winter is coming, along with mittens, cold hands, snow, and jackets. Now that we’re all carrying around lithium batteries in our pocket, wouldn’t it be a great idea to build an electronic hand warmer? That’s what [GreatScott!] thought. To build his electronic hand warmer, he turned to the most effective and efficient way to turn electricity into heat: a ten-year-old AMD CPU.

Building an electronic hand warmer is exceptionally simple. All you need is a resistive heating element (like a resistor), a means to limit current (like a resistor), and a power supply (like a USB power bank). Connect these things together and you have a hand warmer that is either zero percent or one hundred percent efficient. We haven’t figured that last part out yet.

Because more power and more retro is more betterer, [GreatScott] pulled an AMD Sempron out of an old computer. Finding and reading data sheets is for wimps, apparently, so [GreatScott] just poked some pins with a variable power supply until the CPU was drawing about 500mA at 5V.

The video continues with some Arduino-based temperature measurement, finding some new pins to plug the power leads into, and securing all the wires on this heating element with hot glue. For anyone in the comments ready to say, ‘not a hack’, we assure you, this qualifies.

With the naive method of building a CPU hand warmer out of the way, here’s the pros and cons of this project, and how it can be made better. First off, using an old AMD processor was a great idea. These things are firestarters, and even though this processor preceded the 100+ W TDP AMD CPUs, it should work well enough.

That said, this is not how you waste power in a CPU. Ideally, the processor should do some work, with more active gates resulting in higher power consumption. If this were an exceptionally old processor, a good, simple option would be freerunning the chip, or having the CPU count up through its address space. This can be done by tying address lines low or high, depending on the chip. That’ll waste a significant amount of power. Randomly poking pins hoping for the right power consumption is not the way to get the most heat out of this CPU.

Of course, the above paragraph is just theory. The eating is in the pudding, or some other disfigured colloquialism, so here’s a quad-core 386 coffee warmer. This project from [magnustron] uses four 80386 CPUs powered via USB to make a nice desktop hotplate for your cuppa. Of course being powered by USB means there’s only 500mA to go around, and the ΔT is comparable to [GreatScott]’s AMD and hot glue hand warmer. Thus we get to the crux of the issue: 5V and 500mA isn’t very hot. Until cheap USB-C power banks, with ten or twelve Watts flood in from China, the idea of a USB powered heater is a fool’s errand. It does make for some great AMD firestarter jokes, though, so we have to give [GreatScott] credit for that.

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A Ride Into Space, But Nothing Fancy

October 5, 2010 by 67 Comments

[Luke Geissbuhler] wanted to send something into space, a fun project his kids could get in on too. Instead of sending up a suite of electronic components they went with consumer electronics. The key element, an HD camera to record the event, is protected by a styrofoam shell and soft foam padding. To help ensure that the device was recovered an iPhone also made the trip, running a GPS tracking program that continuously updated the package’s location. To combat the ill-effects of severe cold some chemical hand warming packs also joined the flight.

As you can see after the break, it was a success. The camera documented an incredible ride, with a balloon rupture at 19 miles above the earth (that must be a calculated height as there’s no altimeter in the package). The pod came down gently thanks to a parachute and was recovered just 30 miles from where it launched.

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