Yoshizen's Blog

Simple Arithmetic (2)

Was that the nature of Chinese electronics, I’m not sure, the LED ring light on a Z-light arm stop to work less than a month = switching control unit has brake down. Still, connecting the USB power direct, LED light itself can be light on. —– Then wait a moment. LED power is 5V, the Ring light was said to be 8W = its mean this lighting unit was designed somewhat for less than 2A (8W / 5V = 1.6A) (and anyway, the USB adaptor was 2A Max).

Connecting USB 5V direct to the LED light can be used though, it will be an over current to both LED and USB adaptor = soon they will be burnt out. To save the broken LED ring light, it is necessary to take a measure to limit the current = need to connect a resistor. To limit the current to 2A with 5V, we need a 2.5 Ohm resistor.

So, I connected 2.2 Ohm resistor (this type of resistor is getting harder to find though) (Why the wire of resistor was not cut short was, it get hot = need to disperce the heat) ( Note, for a sake of clarity, the photo was taken before applying insulation tape. )

With some improvisation, the LED light was rescued (though, without the brightness adjustment) —– I noticed that now, we can get the same LED light on Z-light arm for as cheap as £14 ! —– some of them may not break down. —– or am I expecting too much for £14 ? 😀


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