Advice: Dimmable flashlight driver that can be controlled via microcontroller

Pseudowok

Newly Enlightened
Joined
Jun 21, 2017
Messages
3
Hi all,

I am looking for recommendations for an LED driver. I'm trying to create a dimmable, single, high-intensity led setup for use in lanterns. I would like to control the dimmer using a microcontroller, which I assume means the driver needs a PWM input. I have been playing around with an arduino, and have a nice flicker effect using PWM, so I would like to be able to replicate it with a nice cheap microcontroller. I have a bunch of old lanterns that I want to retrofit, so cost is a concern.

I am new to electronics in general, which is why I'm trying to find something somewhat ready-made. I don't mind wiring multiple parts together, but I'd rather not be constructing things from scratch / ordering custom parts. I've been lurking on these forums looking for insight, but mostly feel like I'm spinning my wheels.

I want to use a microcontroller so I can:

1. Create fluctuations in the light, like a candle
2. Control the overall brightness, so the fluctuations will occur around a set brightness.

Required:
  1. Microcontroller built in OR the ability to dim using an external microcontroller. I want to be able to control the overall brightness with a potentiometer, and have the circuit control the flickering around that set intensity.

Preferred:
  1. Run off a single AA battery
    • If it has a built in boost, great, but I am happy to add a boost circuit in. I could also go Li-ion. It seems like most of the drivers I have found that are dimmable require at least 5v. It hasn't been clear to me if any of them take PWM input, so I can't get the flickering effect.
  2. Small
    • Ideally this will be in a compact format so I just pop it into a lantern in place of a candle / oil reservoir.
  3. Cheap
    • Something under 10 bucks. I want to make a number of these to update a collection of lanterns. I realize I might have to buy a cheap IC to do the PWM separately. I suppose if the controller is integrate I can go higher, but I would like it to be fully programmable.

I truly appreciate your expert advice, I'm happy to do my research, I just need help getting pointed in the right direction!

Thanks!
 

DIWdiver

Flashlight Enthusiast
Joined
Jan 27, 2010
Messages
2,725
Location
Connecticut, USA
I'd guess that you will not find a driver that can boost from 1.5V or less and accept PWM input. If you can talk about a LiIon cell, or 3x 1.5V cells (since they won't hold 1.5V very long), you've got lots of options.

With modern LEDs with lower Vf, a 3.0-4.2V power supply range lets you use the widely available AMC7135 driver chips. Add a micro and maybe an FET, you're done!

There are scores of different '7135 boards around, typically with 1-8 chips, each chip providing 350-400 mA of output. Here's an example: http://www.dx.com/p/2-7v-6v-3w-cree-circuit-board-for-flashlights-15mm-2-7mm-25518#.WUxd2Gjyu70 This board has two chips fitted and room for another. It has no micro, so no modes, dimming, etc.

http://www.dx.com/p/1050ma-constant...circuit-board-module-3-4v-127686#.WUxeVmjyu70 This one has a micro onboard to provide modes, dimming, etc. The output pin of the micro controls the '7135's directly. Some of the micros can be reprogrammed, or replaced with one that can be.

I think there's some folks around who have hacked some of the boards, and have sample code available.
 

Pseudowok

Newly Enlightened
Joined
Jun 21, 2017
Messages
3
Hey DIWdiver,

I've been having trouble logging in from my phone, thanks for the reply. I took your advice and am discounting a driver with boost built in for AA. I followed your links and spent some more time looking around and I think a constant current driver with the 7135 chips and an Amtel Tiny13a is what I will settle on. Thanks for pointing me in the right direction, I already have a few picked out.
 

rayman

Flashlight Enthusiast
Joined
May 6, 2008
Messages
1,219
Location
Germany
Welcome to CPF btw ;-),

Sounds interesting. I did something similar with a 3W RGB LED and a PT4115 circuit board, which can be controlled over PWM. I did the controlling with an Arduino that time. So let us know how your project is proceeding ;-).
 
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