USB-C Powered Hotplate Is Not For Food

Once upon a time, it was deemed mostly silly to try and schlep power from a computer’s ports. Then it was kind of amusing to do so with USB, and before you knew it, we were running whole laptops off what started out as a data connector. These days, it’s not unusual to run a soldering iron off USB-C, or, as [MarkTheQuasiEngineer] has done—a hotplate!

This hotplate is not for quesadillas, nor samosas. Instead, it’s a tiny hotplate for tiny reflow tasks. Given many PCBs are quite small, there’s no need for a huge hot plate to get your circuits assembled.

The device relies on metal ceramic heating elements to provide the warmth. An NTC thermistor is used for monitoring the temperature for accurate control, which is handled by the STM32 microcontroller that’s running the show. It also drives a small display indicating the mode of operation and current temperature. The STM32 controls the power going to the heating element from the USB-C feed with a stout power MOSFET.

Sadly, the project hasn’t been a complete success. With a PCB on the plate, [MarkTheQuasiEngineer] was only able to achieve peak temperatures of around 200 C. That’s not great for doing proper reflow, but it’s a start. He believes upgrading to a more powerful supply to feed the hotplate will help.

We’ve featured some other great reflow hotplates before too.

17 thoughts on “USB-C Powered Hotplate Is Not For Food

      1. Before IBM redefined already established industry standards with their PC, it was quite common that computers and peripherals would provide power with otherwise unused pins on interface connectors. Often used for ancillary equipment like protocol converters, current loop adapters, termination networks and similar stuff. Back then, users and operators were expected to have enough technical knowledge to RTFM and use or build appropriate cables.

  1. so its a USB hotplate designed to reflow boards, but it doesnt get hot enough to reflow boards, so it needs a more powerful supply though usbC can do what? a couple hundred watts

  2. Maybe it’d benefit from a lid. Put one of those glass cake domes over it… Massively mitigate power lost to convection.

    That’ll let you hit higher temps without pulling more watts.

    1. Make sure glass is made of borosilicate as they are better suited to hot and cold and won’t shatter easily if you took it off while hot and absent-mindedly placed the hot glass cover onto cold surface. The cheap, common soda lime glass will shatter quickly and easily from thermal shock.

      1. I’ve always preferred the “don’t absent mindedly handle hot objects” approach to life.

        Regular glass will almost certainly be fine if you plan ahead and have a place to put it.

    2. Or just use a low-temperature solder paste. The one I use needs just 165°C. This is also handy for “finishing” boards (ie putting on the last components or “the other side” that JLCPCB wasn’t able to do cost effectively), since my new components can be hot plated without disturbing the existing 60/40 solder components.

  3. Every each other day a gentle old lady come to home to sell hot quesadillas, they are delicious! made with ‘masa de maiz’ not that commercial fluor. Quesadillas de papa, quesadillas de queso (I mean the original one) quesadillas de frijol and quesadillas de chorizo. damn good bruh!

  4. Q1 is an interesting pick: Infineon IRLR8726 is a linear-capable logic-level 30V 86A NMOS “StrongIRFET” in a DPAK SMT package. RDSon @ 10V = 5.8 mΩ max, RDSon @ 4.5V = 8 mΩ max. The part comes with a downloadable unencrypted multi-level Spice model (irlru8726.spi). Digikey lists the part as: 17,708 In-Stock, Qty-1 @ $0.62 each, Qty-100 @ $0.37 each, Qty-1,000 @ $0.23 each (Mouser is a tad cheaper tonight). I briefly tested the IRLR8726 Spice model in ADI’s LTspice (x64) v24.0.12 and it seems to work fairly well. In simulation, Vgsth at ~2.6V seems slightly high compared to the datasheet room temperature specification, but for the intended hot-plate application that’s fine.

    https://www.infineon.com/cms/en/product/power/mosfet/n-channel/irlr8726/

    https://www.infineon.com/dgdl/irlru8726.spi?fileId=5546d462533600a40153573edb653e54

    https://www.digikey.com/en/products/detail/infineon-technologies/IRLR8726TRPBF/2354150

    Read these related application notes:

    Linear Mode Operation and Safe Operating Diagram of Power-MOSFETs

    https://www.infineon.com/dgdl/Infineon-ApplicationNote_Linear_Mode_Operation_Safe_Operation_Diagram_MOSFETs-ApplicationNotes-v01_00-EN.pdf?fileId=db3a30433e30e4bf013e3646e9381200

    Some key facts about avalanche

    https://www.infineon.com/dgdl/Infineon-ApplicationNote_Some_key_facts_about_avalanche-ApplicationNotes-v01_01-EN.pdf?fileId=5546d462584d1d4a0158ba0210977cde

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