My first project!

Discussion in 'The Projects Forum' started by DR1, Sep 13, 2012.

  1. DR1

    Thread Starter New Member

    Sep 13, 2012
    I've been cramming electronics into my brain all week and most of it has actually been staying in.:D But I have a couple questions I havent been able to grasp or find answers to on this or other sites. Sorry if they seem trivial.

    I'd like to control 2 strands of rgb leds(5050s) as well as a 1W rgb led using an Atmega328 with a ULN2803 and some N Channel Mosfets. I've been using an Arduino Uno but I'd like to try making my own PCB with the 328.

    My first question is, the led strips take 12v while the microcontroller of course takes 5v. All the examples I've seen on the internet have the setup being powered by two power sources(12v and 5v.) Is it possible to use just one 12v source to power the lights and the 328 chip with a 7805 voltage regulator? If not, is it possible to use a 5v power source to power the micro while bumping up the 5v to 12v to supply power to the leds?

    Also, with that 1w led, would I need a driver or is the ULN2803s 500mA output rating be enough to not need one?
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    It's better to use 12V and a 78L05 to power the micro.

    U don't need the 2003 if u got mosfets. they are better. Logic level fets can take 5V gate voltage to fully turn on. The mosfet supply can be 12V.

    You can choose the drain current ratings from data sheets for any LED wattage.
  3. DR1

    Thread Starter New Member

    Sep 13, 2012
    Thanks for the reply.. So, how would I draw that up on a schematic? Is it as simple branching out the 12v source one way to the mosfets and the other way to the 7805 regulator?

    Though I dont want to get over my head for my 1st project, so I'll stay with just leds for now, I'd like to also add 3 stepper motors to the circuit once I get the lights up and running. Would I be still be able to control 3 steppers along with the 3 leds off the Atmega328 alone? Just add 3 more mosfets?
  4. #12


    Nov 30, 2010
    1) yes.
    2) I don't know.
  5. DR1

    Thread Starter New Member

    Sep 13, 2012
    Looking at my Arduino Uno which uses the 328, it only has 5 PWM outputs. So I'd need to use a different Atmega chip with more outputs I guess.