Question about led drivers

[lomabroly]

Hi everyone. I'm new to the forum and just recently became interested in flashlights I've done quite a bit of research and have decided to try my hand at building a flashlight. I have a question that i have not been able to find an answer to by search this forum or the internet at large. If I just missed it, my apologies.

The way I'm understanding it, if a led driver has a voltage range the max output will only be at the top of the range. For example, this board has a max voltage of 4.5 but it says it will work with 3.7 lithium battery. So will it not get the boards full output if I were to use a 18650 battery? If i use 2 cr123 batteries, that would be more then 4.5 volts. Would the board just drop the voltage down to 4.5 or would it fry the board?

Thanks for your help.

 

[Preamp]

Hi there :welcome:.

You got that wrong. The board will deliver constant output (well, almost) with an input voltage in the range of 2.6V-4.5V. That's what the driver is supposed to do. As the manufacturer suggests, you shouldn't use more than 4.5V as this will actually cause damage to the driver. On the other hand, 2.6V might be too low for the board to start working, but it will work until the battery voltage drops down to 2.6V. Note that this is quite low for a single cell, you should not go much lower than 3V for best longevity. Some protected cells out there might "cut off" at 3V, before the driver board.

Regards, Lasse

EDIT: Just saw on the picture that an ATTiny13 is used. It will work fine with 5.5V and tolerates 6V. This is definitely the upper limit, going even higher will decrease it's lifetime, maybe down to 0% in a second... All the other parts will be fine with 6V.