PIC16/PIC18 with >10bit DAC

Discussion in 'The Projects Forum' started by sasek, May 3, 2010.

  1. sasek

    Thread Starter Member

    Jan 3, 2010
    hai all......

    i want control input of optocoupler (LED) using pwm/DAC 10bit. Reason i want to used it because i want control the LED smoothly that is around <4mV for each variable......so i need PIC that have >10bit pwm/DAC. Because right now i use 8bit DAC n the result is bad....the optocoupler become so sensitive
  2. SgtWookie


    Jul 17, 2007
    You do know that LEDs need to be controlled via current and not voltage, right?

    Use a resistor to limit the maximum current through the emitter when the DAC output is full scale. Depending on your optocoupler, the Vf @ 10mA current might be 1.4v, and your DAC output might be 5v at full scale. You might be using a 5v supply to power your PIC.

    So for the above example, you will need a current limiting resistor that is (5v-1.4v)/10mA = 3.6/0.01 = 360 Ohms.
  3. Markd77

    Senior Member

    Sep 7, 2009
    I like the 12F683 if you want 8 pins and 16F819 if you want 18 pins. They both have 10 bit ADC and PWM.

    oops, missed the >10 bit part of the post.