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修理作業が必要なデバイスに対して使用する電子装置の使用方法を紹介します。

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LED and USB connection advice.

i am a serial restorer and upcycler have done many lamps previously but they’ve all been 240v (UK).

i now want to venture into LED lamps powered by USB. USB is 12V which means i need a transformer….or do i?

my question is the following: if i buy 12V G4 LED lightbulbs with their corresponding socket am i able to simply wire them up using a USB cable and that’s it? I am not an expert but i was thinking if the bulbs are already 12V i wouldn’t need a transformer from 240V to 12V? any advice is greatly received. I’d be looking to run these lights from normal power banks and/or laptop USB ports. (the reason i want to avoid a transformer as it’s a bulky item and the lamp i have in mind is small, the transformer will just ruin it)

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Caveat Emptor: You are trying to do or modify something that is connected to mains voltage. Please tread very carefully and do additional research.

A few notes on your question and assumptions.

  • USB is a 5V device, not a 12V device
  • A lamp that was designed to handle G4 bulbs will already have a 12V transformer built in.
  • If you just want to power the G4 LED bulb (in it’s accompanying socket), then you need a 12VDC, constant current power source. The current required will vary depending on the bulb so it would be best if you have the specs. If not, you can tinker a circuit in series with a multimeter and play around with different current levels. Higher current will give a brighter output but also shorten life.
  • If you want to stick with USB (5V), then you can find individual, high brightness LED’s and create a drive circuit with a series resistor to modulate the required curent.

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Emil さん、ありがとうございました!
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