Pyra Prototype Videos - Askarus Edition

klapse

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Thank you for the video, Askarus.

Very nice performance, imo.

The lack of news is disconcerting though. [looks at calendar]
 

EvilDragon

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Well, you can increase the frequency to make the flicker less visible, or put an LC filter on it. Adding a filter increases the component count, as you have to fit a capacitor and inductor on the PCB.
Well, increasing the frequency isn't easy, as we looked into various PWMs and there wasn't a better one... but the LC filter is a possibility. The Display board is a pretty simple two-layer board, adding two components is no big deal.
Can easily be hacked onto existing boards within minutes. I'll check :)
 

slaeshjag

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Imo, the filter should really be on the input side of the backlight step-up regulator, making the PWM signal an analog value. That lets the switch-mode powersupply regulate brightness at hundreds of kHz instead of what, 100 Hz? The regulator driving the backlight supports this mode.

I'd imagine an LC filter capable of filtering at 100-ish Hz and 10's of mA to be quite large, but it's been a while since I last used LC filters, so I might be wrong...

Although, atm, we really don't need more delays ಠ_ಠ
 

Ted

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Well, increasing the frequency isn't easy, as we looked into various PWMs and there wasn't a better one... but the LC filter is a possibility. The Display board is a pretty simple two-layer board, adding two components is no big deal.
Can easily be hacked onto existing boards within minutes. I'll check :)
Great to hear this, :)
 

OppositeDay

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Well, increasing the frequency isn't easy, as we looked into various PWMs and there wasn't a better one... but the LC filter is a possibility. The Display board is a pretty simple two-layer board, adding two components is no big deal.
Can easily be hacked onto existing boards within minutes. I'll check :)
(Low-frequency) PWM was my main hang-up about the Pyra, great to hear this!
 

Failbert

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Oh wow, I might as well start meeting people and having friends, these messaging apps run so fast I am going to become a succesful and respected person so quick I don't know if I will be able to keep up responding to everybody!!!!

Thanks for the vids guys, in the absence of some big text news these can satisfy the thirst very well :)
 

neko

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I'd imagine an LC filter capable of filtering at 100-ish Hz and 10's of mA to be quite large, but it's been a while since I last used LC filters, so I might be wrong...

Although, atm, we really don't need more delays ಠ_ಠ
You're not wrong. Essentially, the coil and capacitor must store enough energy to keep the LED lit during the off cycle. How large these need to be depends on how much power the LED uses, but I'd guess something around 1mH and 100 uF. That could take a few square centimeters of board space.

Changing the power supply to the LED to one that provides better control over voltage and current would be the ideal solution, but it's probably not feasible to redesign that at this point.
 

Ted

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You're not wrong. Essentially, the coil and capacitor must store enough energy to keep the LED lit during the off cycle. How large these need to be depends on how much power the LED uses, but I'd guess something around 1mH and 100 uF. That could take a few square centimeters of board space.

Changing the power supply to the LED to one that provides better control over voltage and current would be the ideal solution, but it's probably not feasible to redesign that at this point.
Based on some laptop reviews on notebookcheck.net, very high frequency could also helpful and many devices using this solution.

Sent from my SM-G900F using Tapatalk
 

Binky

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How does What'sApp work on there? I thought the developers had a rather aggressive stance towards open source and reverse engineering, and that everything is tied to a smartphone (or SIM)?

Is the Pyra app based on bits of the Android client? or using a smartphone as a proxy?
 

EvilDragon

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Based on some laptop reviews on notebookcheck.net, very high frequency could also helpful and many devices using this solution.
Just a quick update here: A coil and capacitor does NOT work. The reason you use PWMs for LEDs is because LEDs want a stable voltage. Otherwise, you will reduce their lifetime drastically.

However, the PWM can be programmed via software and could even run at 500Hz.
But then the maximum brightness is lower than it could be. Right now, the PWM frequency is setup in the device tree (so it's fixed), but it could be possible to put that in userspace so everyone can setup his favourite PWM frequency for each brightness :)
 

Binky

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favourite PWM frequency for each brightness
Could this be automatically chosen to minimise audible harmonics?

500Hz may be high enough to be invisible, but it's firmly in the audible range, and inductors have a habit of susurating.
 

EvilDragon

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Could this be automatically chosen to minimise audible harmonics?

500Hz may be high enough to be invisible, but it's firmly in the audible range, and inductors have a habit of susurating.
You can hear your TV when it runs with 200 or more Hz? :O
 

Binky

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You can hear your TV when it runs with 200 or more Hz? :O
I can definitely hear 200Hz sounds when they're there to be heard, yes. I'm young enough that my ears cover most of the standard 20kHz - 20Hz range.

That said, none of my displays are at all audible - presumably because the designers did a good job!
 

levi

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I think he means the v-sync frequency, which on some modern sets instead of being 50Hz or 60Hz (depending on where you live) is quadrupled with interpolated fields being shown between the vsyncs.

I certainly recall old sets where you could hear the h-sync circuit especially while the set was cold. That's with old hulking great CRTs in faux wooden boxes though, so the circuits probably weren't tip top by the time I got to them anyway, and probably it was the horizontal electromagnets shifting some rusted bit a chassis to and fro slightly - not problems you get since we went thin.
 
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