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Holding a DMD pattern steady in the LightCrafter 9000

Jimmy Chau
Prodigy 20 points
Other Parts Discussed in Thread: DLPC900, DLP9000

In the LightCommander 9000 EVM, will the DLPC900 controller allow me to to hold the DMD in a fixed pattern (that is, without returning mirrors to the flat/reset position)?  We want to be able to dynamically generate monochromatic (black and white) patterns from a computer and have the DMD hold this pattern until the next one is set.  

It seems like this would be impossible in video mode since the controller automatically cycles between the red, green, and blue colors.  From my understanding, all of the mirrors would be brought back to the flat/reset position between each color, even if the red, green, and blue patterns were identical.  And, it would also reset every mirror back to the flat position between every video frame.  Is my understanding correct?

If so, would it be possible to do this with pattern-on-the-fly mode instead?  Section 4.2.3.4 of the DLPC900 Programmer's Guide seems to indicate that we can have 1-bit bit-depth patterns, but Section 4.2.4 specifies 24-bit BMP images (which I assume are color images).  Can I use pattern-on-the-fly mode without automatically cycling between red, green, and blue?

Also, how long can I safely leave the DMD mirrors in a fixed position?  The DLPC900 Programmer's Guide and some of the other documentation seems to indicate that leaving the mirrors in their on or off state for a long time will cause damage and suggests either parking the mirrors in the flat/reset position or enabling "Idle Mode" as often as possible.  

Thanks in advance,

-Jimmy

  • 0
    TI__Expert 6370 points

    Hi Jimmy,

    An operating DMD will always have resets. However, resetting a micromirror to the same position, called a same-side transition, does not return the mirror all the way to the flat state during the reset. The mirror instead experiences a small bounce before returning to its same state.

    On the DLP9000, the maximum time between resets in Video Pattern Mode (which is different than video mode), Pattern on the Fly, or Pre-Stored pattern mode, is about 10 seconds. During a reset to the same image, you are correct in assuming that every mirror experiences a reset with a same side transition.

    The 24-bit image that the programmer's guide is referring to is a composite image. No matter what bit-depth your images are, they are packaged into a 24-bit composite image. This could be 24 1-bit images, 3 8-bit gray scale images, etc. The DMD itself is unaware of color, the red, green, and blue can be ignored for monochrome applications.

    The DLP9000datasheet has a graph (Figure 1) of the DMD derating curve, staying below the curve maximizes the lifetime of the DMD. There is not a strict rule for how long you can leave the DMD in a fixed position, but if you do, turn on "Idle Mode - 50/50 Duty Cycle" as often as you possibly can to maximize the lifetime of the DMD and reduce the risk of "hinge memory."

    Best regards,

    Trevor

  • 0 in reply to Trevor Dowd
    Prodigy 20 points

    Thank you for your answers, Trevor!

    -Jimmy