Skip navigation
TechXchange
Digi-Key TechXchange Communities > Projects and Designs > Discussions
4220 Views 1 Reply Latest reply: Feb 28, 2014 8:59 AM by davecuthbert RSS
Currently Being Moderated

Jan 26, 2014 4:48 PM

Interfacing and controlling a high brightness LED to a microcontroller

I have to build a device where a circuit will flash a high brightness white LED. The flash frequency and intensity will be controlled by a PIC microcontroller. The frequency will vary from 1 to 12 Hz and the intensity will be controlled using PWM. The microcontroller part is not a problem: one of the PIC pin is toggled on and off at a low frequency, and the PWM signal (5KHz, variable duty cycle) is sent to another pin. These two pins are connected to the inputs of an AND gate, the output of the gate controlling the LED. I need some advices about choosing and connecting the right LED, the right LED driver and the right power supply.


The LED intensity must be in the 150 to 200 lumen range.


I have found this LED:

http://www.digikey.ca/product-detail...671-ND/3694225



141 lumen at 200mA, input voltage 5.2~5.3V. It is supposed to include the driver circuitry, although I haven’t seen it in the datasheet. Can I just use a 6V voltage regulator (MC7806CT), thru a transistor driven by the AND gate and connected directly to this LED? Also, do I have to use some sort of heatsink?


I also consider this LED:

http://www.digikey.ca/product-detail/en/A008-EW830-Q2/788-1044-ND/2720735



In this case, what should I use for driver, power supply and heatsink? What’s the best way to connect it to my AND gate?


By the way, I have this driver right now:

http://www.jameco.com/webapp/wcs/sto...001_2156287_-1

Can it be useful?


I’d really appreciate some hints.

Thank you in advance and have a nice day.


Marc

  • davecuthbert Apprentice 87 posts since
    Feb 18, 2014

    The two LED modules appear to consist of LEDs with current limiting resistors. If so, they can ideal for PWM. The driver you list though is a fixed constant current and is not suitable for PWM. To interface your PIC to the LED module all that is needed is a logic level N-channel MOSFET. The 100 ohm resistor is to reduce the propensity for the FET to oscillate and it slows the current rise time, thereby reducing EMI.

     

    The 10uF - 1ohm - 1uH - 10uF filter is to reduce HF switching noise on the 6 volt bus.

     

    Capture1.JPG

More Like This

  • Retrieving data ...

Bookmarked By (0)

Legend

  • Correct Answers - 4 points
  • Helpful Answers - 3 points