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LED's connected to a 9V AC/DC transformer and something went terribly wrong Answered

I recently did a project with 4 LED's 3.3V 25mA 2 in each series (2 parallel circuits). I know i wasn't drawing too much from the transformer but my transformer still melted(ish). It was connected to a switch, but i may i had it connected wrong. I searched for shorts first, and couldnt find any. Would this happen becuase i connected the switch incorrectly? I cannot find much information on using AC/DC transformers for LED's....I was looking to save money on batteries for my projects.


Do you know the actual current draw from the transformer when it failed?

Were your LED's damaged? If so you may not have had a current liminting resistor in series with them, or your resistor was too small a value.

If you had connected your switch in parallel with the LED strings instead of in series, then the transformer would have been directly shorted out.

It's hard to say without a diagram, but the things I listed above are the more obvious ones that come to mind.

Ahh i was so stupid, the resistor i was missing one....obvious answer thank you!