heater

38 Articles

MOSFET Heater Is Its Own Thermostat

March 29, 2023 by 16 Comments

While we might all be quick to grab a microcontroller and an appropriate sensor to solve some problem, gather data about a system, or control another piece of technology, there are some downsides with this method. Software has a lot of failure modes, and relying on it without any backups or redundancy can lead to problems. Often, a much more reliable way to solve a simple problem is with hardware. This heating circuit, for example, uses a MOSFET as a heating element and as its own temperature control.

The function of the circuit relies on a parasitic diode formed within the transistor itself, inherent in its construction. This diode is found in most power MOSFETs and conducts from the source to the drain. The key is that it conducts at a rate proportional to its temperature, so if the circuit is fed with AC, during the negative half of the voltage cycle this diode can be probed and used as a thermostat. In this build, it is controlled by a set of resistors attached to a voltage regulator, which turn the heater on if it hasn’t reached its threshold temperature yet.

In theory, these resistors could be replaced with potentiometers to allow for adjustable heat for certain applications, with plastic cutting and welding, temperature control for small biological systems, or heating other circuits as target applications for this type of analog circuitry. For more analog circuit design inspiration, though, you’ll want to take a look at some classic pieces of electronics literature.

New Possibilities From Fading Lighting Technology

February 25, 2023 by 54 Comments

Like the incandescent bulb before it, the compact fluorescent (CFL) bulb is rapidly fading into obscurity as there are fewer and fewer reasons to use them over their LED successors. But there are plenty of things to do with some of the more interesting circuitry that made these relatively efficient light bulbs work, and [mircemk] is here to show us some of them.

Fluorescent bulbs require a high voltage to work properly, and while this was easy enough for large ceiling installations, it was a while until this hardware could be placed inside a bulb-sized package. When removed, the high voltage driver from the CFL is used in this case to drive a small inductive heating coil circuit, which can then be used to rapidly heat metals and other objects. After some testing, [mircemk] found that the electronics on the CFL circuit board were able to easily handle the electrical load of its new task.

When old technology fades away, there are often a lot of interesting use cases just waiting to be found. [mircemk] reports that he was able to find these light bulbs at an extremely low price due to low demand caused by LEDs, so anyone needing a high voltage driver board for something like a small Tesla coil might want to look at a CFL first.

Filament Dry Box Design Goes Way Over The Top

February 15, 2022 by 36 Comments

There’s a fine line between simple feature creep and going over the top when it comes to project design. It’s hard to say exactly where that line is, but we’re pretty sure that this filament dry box has at least stepped over it, and might even have erased it entirely.

Sure, we all know the value of storing 3D printer filament under controlled conditions, to prevent the hygroscopic plastics from picking up atmospheric moisture. But [Sasa Karanovic] must really, REALLY hate the printing artifacts that result. Starting with a commercially available dry box that already had a built-in heating element, [Sasa] took it to the next level by replacing the controller and display with an ESP32. He added a fan to improve air circulation inside the enclosure and prevent stratification, as well as temperature and humidity sensors. Not satisfied with simply switching the heating element on and off at specific setpoints, he also implemented a PID loop to maintain a constant temperature. And of course, there’s a web UI and an API available for third-party control and monitoring.

The video below details [Sasa]’s design thoughts and goes into some detail on construction and performance. And while we may kid that this design is over-the-top, what really comes through is that this is a showcase for design ideas not only for one application, but for hardware projects in general. There are certainly simpler heated dry box designs, and zero-cost solutions as well, but sometimes going overboard has its own value too.

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Jet burner and close-up

$7 Tent Heater Provides Comfort On A Budget

January 6, 2022 by 120 Comments

At Hackaday’s Minnesota office, we appreciate central heat and hot coffee because the outdoor temperature is sub-zero in Celsius and Fahrenheit. Not everyone here has such amenities, and families living in tents could use heater help. If you live somewhere inhospitably cold and have the resources (time being the most crucial), please consider building and donating alcohol jet burners.

Alcohol burners like these are great for tents because if they tip over, they self-extinguish. You can fill them with 70% rubbing alcohol and they’ll heat a small space, and if running on denatured alcohol, they can be used to cook with. They won’t do you much good outdoors unless you have significant wind protection, as the tiny jet is likely to blow out. The first time you light one, you must heat the coil with a lighter or another heater to vaporize incoming fuel, then it can sustain itself by wicking fluid up from the reservoir jar. Relighting after a tip or accidental gust only takes a spark since the copper is already hot.

If you came for a hack, note how they fill the small tubes with salt funneled through a condiment cap before bending them. Sure, there are springy pipe bending tools, but who doesn’t already have salt and tape? Keeping humans warm is crucial, but heating metal takes a different approach.

Thank you for the tip, [cyberlass]

an up-close of the PCB hotplate

Using A PCB To Reflow PCBs – Take 2!

October 6, 2021 by 29 Comments

It’s not too hard to make your electronics project get warm. Design your traces too small, accidentally short the battery inputs together, maybe reverse the voltage going to your MCU. We’ve all cooked a part or two over the years. But what about making a PCB that gets hot on purpose? That’s exactly what [Carl Bugeja] did in his second revision of a PCB hot plate, designed to reflow other PCBs.

[Carl’s] first attempt at making a hot plate yielded lukewarm results. The board, which was a single snaking trace on the top of an aluminum substrate, did heat up as it was supposed to. However, the thin substrate led to the hot plate massively warping as it heated up, reducing the contact against the boards being soldered. On top of that, the resistance was much greater than expected, resulting in much lower heat output.

The new revision of the board is on a thicker substrate with much thicker traces, reducing the resistance from 36 ohms on the previous design to just 1 ohm. The thicker substrate, paired with a newer design with fewer slots, made for a much sturdier surface that did not bend as it was heated.

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Ask Hackaday: What’s The Best Way To Heat A Tent With A Laptop?

September 16, 2021 by 49 Comments

For Europeans, August is usually a month of blistering heatwaves, day after day of cloudless skies and burning sun that ripens fruit and turns we locals a variety of shades of pink. Hacker camps during this month are lazy days of cool projects and hot nights of lasers, Club-Mate, and techno music, with tents being warm enough under the night sky to dispense with a sleeping bag altogether.

Sometimes though, the whims of the global weather patterns smile less upon us hackers, and our balmy summer break becomes a little more frigid. At BornHack 2021 for example we packed for a heatwave and were met with a Denmark under the grip of the Northern air mass. How’s a hacker to keep warm?

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Keep Coffee Warm Through Induction Heating

April 11, 2021 by 13 Comments

Transformers have an obvious use for increasing or decreasing the voltage in AC systems, but they have many other esoteric uses as well. Electric motors and generators are functionally similar and can be modeled as if they are transformers, but the truly interesting applications are outside these industrial settings. Wireless charging is essentially an air-core transformer that allows power to flow through otherwise empty space, and induction cooking uses a similar principle to induce current flow in pots and pans. And, in this case, coffee mugs.

[Sajjad]’s project is an effort to keep his coffee warm while it sits on his desk. To build this special transformer he places his mug inside a coil of thick wire which is connected to a square wave generator. A capacitor sits in parallel with the coil of wire which allows the device to achieve resonance at a specific tuned frequency. Once at that frequency, the coil of wire efficiently generates eddy currents in the metal part of the coffee mug and heats the coffee with a minimum of input energy.

While this project doesn’t work for ceramic mugs, [Sajjad] does demonstrate it with a metal spoon in the mug. While it doesn’t heat up to levels high enough to melt solder, it works to keep coffee warm in a pinch if a metal mug isn’t available. He also plans to upgrade it so it takes up slightly less space on his desk. For now, though, it can easily keep his mug of coffee hot while it sits on his test bench.

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