You know, it occurs to me that your fading of the LED might work better if you supplied constant power to your Buck converter and moved your transistor to be between the LED and the converter.
yeah,. good eye.
this diagram is for NO PWM fading,. as the mosfet arduino pin isn't even PWM. i have rearranged things as a told jshaw for pwm.
i do have a new set up with an additional fet tween the vout of the buck and the led. still no good. i orered a new buck. maybe this one is bad.
Sorry, my mistake, I did not pay attention to your supply. But, what about the following: you only use 1x3.7V supply (instead of 2) and use a boost to give 5V to your Arduino. Then connect your single LED to the 3.7V with PWM. Additional advantage: less space eaten up by batteries (they are big or have limited capacity) and a smaller boost, because the "logic" does not eat so much compared to the HP-LED's.
yup. you are correct sir.
i DO that exactly with the saber i posted as my first build with Sw-200 sensors, back in Dec. 5v buck up, and 3.7v DIRECT to the LED, no resistors as i said,. if you have a 3.3-3.4v LED that can take an Amp,. you don't need resistors at all, due to the internal resistance of the battery. which is about 1 ohm. I am moving to a higher powered green Cree. so i can do more dramatic FoC. and PWM fading, and only use a buck wth the LED instead of the Arduino. i'll change this diagram to illustrate my new goal, and post a diagram for my working one battery set up. which by the way,. is easy to make, change batts, and is cheap.