[ell-i-developers] "LeBulli" Led shield for PoElli

  • From: otso@xxxxxxxxxxxx
  • To: ell-i-developers@xxxxxxxxxxxxx
  • Date: Thu, 19 Jun 2014 15:31:16 +0300

Hi all,

I'm doing a schematic for a high power led driver shield for Ellduino, it
resembles a bit the schematic we have for hackathon. PDF attached.

Led to be driven is
or electrical equivalent.

Since selected LED has low forward voltage, buck topology is used.

Design has following assumptions, please correct me if I'm wrong:

1) 1 A of current can be drawn from 5V pin, which comes from PoE SMPS.

2) Device can receive and transmit information through ethernet port

3) There are 3 open-drain PWM  pins available.

4) Core can run at 48 MHz, so 8-bit PWM can be run at 48 MHz / 2^8 = 187,5

5) Pinout of Ellduino is correct (please check this if nothing else)

I'd also appreciate recommendations for pins to use for PWM. Open-drain
ability is a plus but not necessary. Even better would be to have phase
difference between PWM-signals to avoid unnecessarily high ripple current
on 5V pin.

Do you think I should add power arbiteration from Vin pin of Arduino Mega
for Arduino-friendliness? OTOH, Arduino Mega cannot reach required PWM
frequencies, so using a lot larger chokes and capacitors would be


Attachment: LeBulli.pdf
Description: Adobe PDF document

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