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digi pot

rrrr Posts: 63
edited 2005-04-14 03:59 in BASIC Stamp
hop.gif·hop.gif i am trying to digitally controll the brightness of 24 leds as one unit·in a smooth motion(up and down). is it possible to do this with a digital potentiometer like the ad5220 if so what is the best setup.
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Comments

  • BeanBean Posts: 8,129
    edited 2005-04-14 02:33
    Just use the PWM command, that's exactly what it's used for.
    Bean.

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    ·
  • KenMKenM Posts: 657
    edited 2005-04-14 03:39
    The digital pot will not work well for your application.

    As Bean mentioned, the PWM command will work well.

    Do you know what the forward voltage is for the LEDs you have chosen?

    The forward voltage information is needed to know what series value resistor is needed in·with each group of 4 LEDs.

    The drawing attached has a group of 20 LEDs controlled with one 2n2222 transistor. You will simply add one more group of 4.
    pwm.jpg
    455 x 518 - 22K
    pwm.jpg 22.1K
  • rrrr Posts: 63
    edited 2005-04-14 03:59
    here are the specs for the leds i will use. i will be duplicating the circuit four times in the project each circuit will be a different color led.

    red:
    Forward Voltage (V) : 1.8 ~ 2.2·
    Max Continuous Forward Current : 30mA
    Max Peak Forward Current : 75mA
    yellow:

    Forward Voltage (V) : 1.8 ~ 2.2
    Max Continuous Forward Current : 30mA
    Max Peak Forward Current : 75mA

    white:

    foward voltage min=2.8, typ=3.5, max=4.0

    foward current max=30ma

    blue:

    foward voltage= min=2.8, typ=3.5, max=4.0

    foward current max=30ma
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