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DLPLIGHTCRAFTER: Maximum Current for Pattern sequence

cmz kopqi
Prodigy 110 points

Part Number: DLPLIGHTCRAFTER

The user guide states, that the Light Engine on the DLP LightCrafter 4500 EMV is only capable of handling 4.3 Amps (continuously) with its active cooling system, and yet, the default setting for the RGB lights in video mode is 104 for red, 135 for green and 130 for blue (of a maximum of 255). This should result in a current flow of 7.3 Amps (according to the formula in the user guide, if the foreground is at max brightness), which should cause the DLP to overheat. Does that mean, that I have to reduce the LED Current manually or add a beefier cooling system if I want to get a brighter projection?

  • 0
    TI__Mastermind 20045 points
    Hello cmz and welcome to the E2E forums,

    Good question! The default values should be okay when you have the Automatic LED Selection checked. The sequencer will illuminate the red, green, and blue LEDs at separate times to properly display the image. If you are using the manual LED selection and have more than one LED on at a time then you may need to lower the LED Current. You also may need to lower the current if you are creating sequences where more than one LED is illuminated at once (such as all white, cyan, magenta, or yellow). In the case of the automatic sequencer the max continuous current is actually max(RedCurrent, GreenCurrent, BlueCurrent).

    Let me know if that answered your question!

    -Kyle
  • 0 in reply to Kyle Rakos
    Prodigy 110 points

    Thanks for the response.

    Does that mean that if I had two alternating Patterns (one Green and one Red) with a Bit-Depth of 1 and 235us Pattern Exposure and Period, that both LEDs are being switched on and off at a frequency of 4225/2 Hz?

    Or to put it differently, does that mean, that the mirrors do not choose which LED light they will reflect, but whether or not they will reflect whatever light is currently on?

    *EDIT*

    Also, if possible, could you show me where in the Documentation I can find that Information? It's not that I don't trust you, it's just that I will need some way of confirmation for my supervisor. Thanks in advance.

    Regards.

  • 0 in reply to cmz kopqi
    TI__Mastermind 20045 points

    Hello again,

    Yes, that is correct. However, they will obviously not be switched to full on (they will be PWMed). Unfortunately I do not think there is specific documentation for what you are asking. The DLP overview may help: www.ti.com/.../dlpa059b.pdf

    You could verify this behavior by probing the LED PWM signals on the board. This should show that if you have a sequence with just red, green, and/or blue, the LEDs will only turn on one at a time. 

    Thanks,

    Kyle

  • 0 in reply to Kyle Rakos
    Prodigy 110 points

    Thanks for the link and the help.

    I still have another Question;

    So the PWM signal is necessary to dim the LEDs if the user does not want them to be at full brightness, right? I.e. if the current value for Red would be 148/255 (instead of 255/255) in the GUI, the current would be around 3A (instead of 4.9A) because of the PWM signal, that would have a duty cycle of roughly about 148/255? And in the previous example, that PWM Signal would be turned on and off at 4225/2 Hz? 

    Regards

  • 0 in reply to cmz kopqi
    TI__Mastermind 20045 points
    Hello again,

    The formula's for the current value corresponding to each LED can be found on page 25 of the 4500 user's guide. You can find them copied below.

    Red LED Current (A) = 0.0175 × (LED Current Value) + 0.4495
    Green LED Current (A) = 0.0181 × (LED Current Value) + 0.3587
    Blue LED Current (A) = 0.0160 × (LED Current Value) + 0.1529

    Thanks,
    Kyle