Pro Mode for LED Brightness Modes

Hey there,

I’m wondering if we could implement a pro mode settings to allow manual adjustments to brightness levels? The presets are currently limited to 3 options.

To clarify, I’m not referring to image correction brightness settings. I’m referring to the LED brightness outputs (currently: Energy Saver, Normal and Presentation)

Thank you!

How many brightness options would you like to have in a 800lm projector?

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A sliding scale @Hobbes.

It’s a good idea, but is not very simple to implement, due to multiple reasons:

  • changing LED brightness has thermal implications. The fan speed is not adaptive (yet), which is a prerequisite to adding this feature. Our lab has tested known values for fan speed and led brightness, and hardcoded those to ensure correct operation.
  • the colour balance can change since the relationship is not strictly linear for each of the 4 leds.
  • the led brightnesses are hardcoded inside the kernel. This will need to be changed to save and restore from flash storage.

Nonetheless we’re working on something similar and will keep you posted.


That is a given when running LEDs in constant current mode (output wavelength also changes a bit with current). Will there perhaps also be a way to tune CAIC and LABB as well?

There are many ways to reach close to optimum use of the finite time available per frame. Are you at any point mixing more than one LED color, equivalent to a transparent or yellow color wheel sector? It doesn’t seem to be supported by the DLPA3000 PMIC (not sure which one’s used in the PPM), but it’s not entirely obvious to me how the second blue LED is driven when there’s only three channels in the PMIC.

Having said that, the users have to realize that they are entering a world of pain if they start messing with the color balance in this way if they don’t know what they are doing. I wouldn’t mind experimenting a bit but I’d make doubly sure that I have a backup of the original settings to revert back to when it goes south.

It is important to remember PicoPix Max is a consumer device built for the masses, not for professional installation. A number of simplifications have been made and sane default settings have been hardcoded.

I believe that rules out the ISF Day and Night calibration then :slight_smile:

It totally makes sense, it’s a portable projector after all. The nice thing about the PPM though is that it’s fairly inexpensive which means that it’s automatically a lot more inviting to tinker with than the more expensive “real” home cinema projectors.

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@PhilipsEngineering so your fans are running at constant speeds according to the mode, regardless of the temperature?

  1. Would this imply that once you have adaptive speeds, there is a possibility for the fan to be quieter than it currently is, similar to a notebook cooling fan?

  2. Does this imply that the fans will run at the predetermined speeds regardless of ambient temperature? In India, Pakistan and other regions, summers can be pretty hot and the predefined speeds may lead to meltdowns. :ghost:

  3. With adaptive speeds, is there a possibility of prolonging the life of the components?

  4. We know the LEDs are rated at ~30-50k hours but what is the expected life of the DMD?

@wernerj what do you think about this?

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Let’s see here…

I would say so yes. You don’t want it to lower the speed too quickly though as you’re getting a super annoying varying fan noise. I’d take a static fan at a higher noise level rather than something that can’t make up its mind any day.

Well, just don’t leave it in the sun, that will sure make it unhappy (but who would attempt to use a projector in sunlight). But if it’s still over 35C when the sun is down and the projector is turned on then sure, you’d have less headroom than if it’s used in 20C ambient, but the difference really isn’t that big. I’m more worried about elevated humidity causing corrosion and other bad stuff.

Yes and no. You’d choose between component longevity and low noise depending on how the adaptive algorithm is tuned. Hopefully the PPM fixed speeds should be tuned for the maximum ambient temperature specified, which means that an adaptive speed really wouldn’t drastically improve the life as long as you’re operating the PPM below maximum allowed ambient temperature.

If you look at the very informative datasheet for the DLP230NP DMD around page 24 the expected life is highly dependent on duty cycle which in turn makes it content dependent which will make it very difficult to predict. The DMD will definitely have a longer expected life if it’s kept cooler and exposed to less intense light.

The quoted 30k+ hours for the LEDs is IMHO a fantasy number. Yes most likely the LEDs will still light up at 30k hours, but they will emit nowhere near the luminous flux they initially did and the color balance will likely be quite off due to the fact that the different color LEDs will degrade at different rates.

The good thing about this being a discrete RGB(B) light engine is that the relative duty cycle between RG and B is programmable so this could in theory be compensated for to a degree. In the color wheel based projectors with UHP lamps you would always lose the red at the end of usable lamp life, but the color wheel sectors are static so you’re stuck with less red until the lamp fails altogether. I’ve used up tens of UHP lamps in color wheel projectors and the annoying part is that color balance is changing fairly rapidly the first few hours in a new bulb and also in the last 25% (500 hours or so) of lamp life. With LEDs this is a much slower process.

My guess is that the DMD will last longer than the LEDs will, and most likely something else will have failed before the LEDs do (I’m thinking flash memories and definitely the battery). You also have to consider the likelihood that the projector might become physically damaged in some way before the electronics fails due to age, as this is a portable unit.


@wernerj love your thorough, technical replies and learning from your experiences! Thank you for being here.