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Dim 24v LED strips? — Parallax Forums

Dim 24v LED strips?

SYSY Posts: 11
edited 2007-12-20 19:21 in BASIC Stamp
Could anyone please help me figure out what exactly would I need in order to have the Basic-stamp dim 24v LED strips?
Usually when I control these strips I amplify the Basic stamps output with a relay, this time however I would like to dim them on and off rather than just turn them on/off.

Thanks.
Sharon.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-12-20 19:14
    LEDs are normally dimmed by turning them on and off rapidly so the eye averages the brightness and varying the time on vs. time off. This is usually referred to as PWM (pulse width modulation). You will need a switching transistor. The 2N2222 is typical of one that can handle the 24V and a current of several hundred mA. Download the "Industrial Control" tutorial from Parallax's website and look around page 85 for diagrams and descriptions (www.parallax.com/Portals/0/Downloads/docs/books/edu/ic.pdf).

    Try using the PULSOUT statement to turn on the LEDs for periods of time and the PAUSE statement to wait between pulses. 30 to 60 pulses a second will visually blend together.
  • LilDiLilDi Posts: 229
    edited 2007-12-20 19:21
    SY

    ·The TLC5940 LED driver IC will control up to 16 LEDs. Each of the 16 channels can be dimmed independently in 4096 steps.

    http://focus.ti.com/lit/ds/symlink/tlc5940.pdf
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