Transformers are obviously used to increase or decrease the voltage in AC systems, but they have many other esoteric uses. Motors and generators are functionally similar and can be modeled like transformers, but the really interesting applications are not in these industrial environments. Wireless charging is essentially an air-core transformer, which allows electricity to flow through an otherwise empty space, while induction cooking uses a similar principle to induce current in pots and pans. And, in this case, coffee cup.

[Sajjad]'s project is to try to keep his coffee warm on his desk. To make this particular transformer, he placed his cup in a thick wire coil connected to a square wave generator. The capacitor is placed in parallel with the coil to enable the device to achieve resonance at a specific tuning frequency. Once this frequency is reached, the coil will effectively generate eddy currents in the metal part of the coffee cup and heat the coffee with minimal input energy.

Although this project does not apply to ceramic cups, [Sajjad] did demonstrate it with a metal spoon in the cup. Although it will not be heated enough to melt the solder, if there is no metal cup, it can keep the coffee warm in a critical juncture. He also plans to upgrade it so that it takes up slightly less space on his desk. However, for now, when it is placed on his test bench, it can easily maintain the temperature of his coffee cup.

Thanks [Jerry] for the tips!

I remember my father took his latest work from work home in the early 70s and asked my mother to test boiling milk in an iron pan. It is easy to control the heat with a potentiometer. It made a big buzzing sound and may not pass any modern safety tests, nor can we watch TV, but hey, a prototype induction cooker, we are really impressed. Now I have a consumer-grade induction cooker in the kitchen, which is easy to use and quiet, and I can watch TV. Don't run it when there is someone with a pacemaker around.

Wow, 300W is just to heat a cup? Why not use the 100W resistor mounted on the aluminum plate? When soldering, I use them to heat the PCB with a ground plane. About 25W is enough to raise the temperature of the PCB to 100 degrees. Celsius.

good. Extra space lasers from the US Space Force may be a solution.

Just take a Bodum insulated glass (they are really great!) or clone (cheaper and equally good), install the laser to the ceiling (looks neater), connect some bell wires to the next three-phase Switch box and voila. Coffee reheated immediately.

The power of most coffee heaters is about 17 watts. So why use 25 watts? What about your NE555?

The power of a PCB is 25 watts ;-)

Not 300W, it needs less than 30W

Do not. By continuing to heat the coffee, you will continue to brew coffee. Destroy taste and flavor.

Yes, coffee that is reheated (or heated for a long time) tastes bad. It's best to drink it fresh.

Absolutely. Therefore, the setting requires an automatic milk and sugar drop to cover the taste after being left for too long.

Although this project is great, you should remember that those cheap thermos cups from China are made of very poor stainless steel. At Warsaw University of Military Science and Technology, we tested hot water stored in it for 20 minutes. Compared with water from the same kettle but stored in glasses, the hexavalent chromium content of these cups is dangerously high.

thanks for your reminder. Do you have a link?

While we are discussing this topic, we should also pay attention to cheap "brass" pipe fittings. They usually contain large amounts of lead.

Why not just use a thermos?

Thanks for sharing this video of mine. Thanks also to Jerry.

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