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I have found myself needing small heaters, in the 5-10 watt range for various applications in diy projects, preferably powered from 120VAC. The exact wattage is not important, and doesn't have to have a thermistor.

Ideally, I would love to just use a 3k/10 watt resistor and call it a day, but for safety reasons I know you must use an isolation transformer.

So can I just find the smallest 1:1 0.05A iso transformer I can, fuse it at 0.05 A on the wall side and call it good?

There might be an even better solution though, maybe even something just off the shelf.

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    \$\begingroup\$ Consider an incandescent lightbulb. \$\endgroup\$ – glen_geek Feb 25 at 0:28
  • \$\begingroup\$ an 8 watt bulb or a 35W soldering pen with a dimmer.... I once used a soldering iron suspended by wire in air in a picnic box to make a portable Tenny "cheap & dirty" oven for widget testing then dry ice cubes with a 1W fan to stir and test to -40'C \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 25 at 0:49
  • \$\begingroup\$ you don'r need an isolating transformer if you have sufficient isolation or use a grounded enclosure. \$\endgroup\$ – Jasen Feb 25 at 6:38
  • \$\begingroup\$ a usb phone charger isn't a bad way to go, probably cheaper than a copper-heay transformer. \$\endgroup\$ – dandavis Feb 25 at 18:25
  • \$\begingroup\$ The bulb is a fantastic idea, I will use that. Thank you! \$\endgroup\$ – cat pants Mar 5 at 5:40
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You don't need a 1:1 iso transformer. Just get a doorbell transformer and pick a resistor to suit your needs. Although you can get better prices for lower-power transformers if you go to a distributor such as digikey.com and search.

Going to a lower voltage (say, 24 volts or less) will also be safer, since even if it's isolated, 120 VAC is perfectly capable of killing you if you mess up.

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You don't need an isolating transformer if you have sufficient insulation or use a grounded enclosure.

A hot glue gun uses electrical insulation of the heater, electric blankets, and heating pads do this too.

A soldering pencil uses an earth connection for safety, same with portable hotplates, and some electric jugs.

Mount a 10W resistor inside a grounded metal emclosure,

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