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I have a number of very small 40mm cooling fans which I want to run inside of a device I can move around my home. (Its for a crafting project.) Ideally, I'd be able to plug the fan into a standard USB charger or the USB outlet that I have on some of my household electrical outlets. (USA)

Even if I had to do a little bit of soldering, what is a somewhat convenient and inexpensive way to step USB charging outlets up to 24V (without providing too much amperage) or stepping 120V (USA) down to 24V (again with the right amperage.)

Thank you all!

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    \$\begingroup\$ are the fans AC or DC? ... 24 Vdc power adapter would be simple and inexpensive ... the "amperage" is irrelevant, as long as it is more than the fans require \$\endgroup\$
    – jsotola
    Apr 14 at 1:38
  • \$\begingroup\$ 5 V 40 mm fans are available if there is not enough space for a DC-DC converter. \$\endgroup\$
    – Andrew Morton
    Apr 14 at 10:38

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You can purchase 2W DC-DC converters with 5V input and 24V output from distributors such as Mouser for about $5:

https://www.mouser.com/datasheet/2/670/pdme2_s-2578683.pdf

For a 24 volt fan, voltage regulation is not critical, so it would be fairly easy to make your own DC-DC converter, generating a 5V 50 kHz square wave into a small transformer with bridge rectifier output. But that probably involves winding your own transformer.

There are boost converters that can provide 24 VDC from a 5 V input, probably only a few dollars. Or you can build your own. I found a boost converter IC that is less than a dollar but you will need to add an inductor and other components, but it's pretty simple.

https://www.mouser.com/datasheet/2/389/mc34063ab-1849936.pdf

Cheapest solution may be a 24V wall-wart, with 120 VAC input.

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    \$\begingroup\$ Surely cheaper than a 5V wall-wart-plus-converter would just be a 24V wall wart? \$\endgroup\$
    – Matti Wens
    Apr 14 at 9:23
  • \$\begingroup\$ Yeah, that's what I meant. Good catch! \$\endgroup\$
    – PStechPaul
    Apr 15 at 0:07

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