Driving 2-4 3.2-3.4v white LEDs?

Hi all,

I’m currently working on a circuit that needs to implement two or four white LEDs as a camera flash. Currently using a Photon but will be moving to an Electron (on battery power) in the near future.

What’s the simplest option for driving the LEDs safely? I want to drive between two and four, they will simply switch on for around 250-300ms and then switch off. At the moment I’m driving a single white LED directly from a GPIO pin with a resistor, but this doesn’t give me the brightness that I need. I’d be aiming for white LEDs with similar characteristics to the one that’s provided in the Maker kit (3.2-3.4v forward voltage, suggested 18mA of current I think). Individual control of the LEDs is not necessary (so they’re either all on or all off).

Are there any really simple LED driver ICs that are good for this purpose?

Thanks!

IMHO for a flash you don’t need any sophisticated circuit / LED driver. For a short flash, a resistor should be sufficient.

Although high power LEDs usually draw lot more than 18 mA, which would be too much for Photon to supply. A simple transistor (or mosfet) circuit would be enough. This describes what you are trying to achieve quite well. Written for Arduino, but circuit should be rather same. You may want to adjust resistor between Photon pin and base for your transistor base current. Or use a mosfet.
For LEDs with forward drop > 3.3V connect to VIN, whatever it would be. Also be sure that your power source can handle LED current.

An extra, beefy cap might also be good to deliver the max current quickly while calming the impact on the Electron and the LiPo.

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