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DLPC350: How to track LED on-time/operating hours

franziskus
Expert 7178 points
Part Number: DLPC350

Team,

is there a way to track the operating hours of the LED (meaning the LED on-time) when using the DLPC350?

Thanks!

  • 0
    TI__Mastermind 20045 points
    Hello Franziskus,

    We do not have a way to track the LED operating hours as part of the controller. A front end controller with customer code would be needed to accomplish this.

    Thanks
    Kyle
  • 0 in reply to Kyle Rakos
    Prodigy 190 points
    Hello Kyle,

    the initial question was from me - Franziskus pushed it into this forum. Now I have registered myself to this forum.

    I agree with you that there is no explicit method from the DLPC350 controller. I had the idea that I could use the PWM input of the dlpc for counting the high (and low) time of either the LED_PWM output or the LED_EN output of the dlpc, readout the register (PWM capture read) e.g. every second. Would this be possible? What is the base frequency of the LED PWM signal?

    Best regards,
    Hagen
  • 0 in reply to Hagen Wiest
    TI__Mastermind 20045 points

    Hello Hagen,

    You should be able to use the three LED output enable signals (LEDR_EN, LEDG_EN, and LEDB_EN). Whenever these are active the corresponding LED will be on. The PWM signals are just used to control LED current. Is that something that also needs to be tracked? You could also measure the LED current across R210 as shown in the Red LED Driver schematic below. The full reference design for the DLPC350 is at www.ti.com/.../dlp4500-c350ref

    Thanks,

    Kyle

  • 0 in reply to Kyle Rakos
    Prodigy 190 points
    Hello Kyle,

    yes, I think tracking the LED_EN will be the easiest way and I will try to use it through the PWM input capture of the DLPC350. Do you see something with this solution that is a possible "show stopper"?

    Best,
    Hagen
  • 0 in reply to Hagen Wiest
    TI__Mastermind 20045 points
    Hi Hagen,

    What do you mean by using the input capture of the DLPC350? You will probably want to capture the enable signals through an external microcontroller (such as a MSP430).

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Prodigy 190 points

    Hello Kyle,

    the DLPC350 has two PWM input channels (GPIO_5, GPIO_6), which can capture a (pwm) signal. One of these channels I want to use for counting the high and low time of the LED_EN. I would route the LED_EN to the GPIO_5 on pcb.

    Best,

    Hagen

  • 0 in reply to Hagen Wiest
    TI__Mastermind 20045 points
    Hello Hagen,

    I believe you should be able to use the PWM input channels; however, let me confirm. Note that you will have to send an I2C command each time you want to sample the input channels which would add a delay from continuously sampling them. Additionally, I am unsure how the PWM input would react to the LED_EN signals. Note the LED_EN signals is not a traditional PWM signal with a constant period. The LED_EN signal depends on the programmed sequence.

    Are you wanting to keep track of LED on time for purposes of LED lifetime? If so it may be better to calculate the LED duty cycle for a given sequence. You can then keep track of how long a given sequence is running.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Prodigy 190 points

    Hello Kyle,

    yes we want to keep track of LED on time for purpose of LED lifetime. Because of the unknown behaviour of the pwm input capture we decided to calculate it in software only.

    Many thanks for your support.

    Best regards,

    Hagen