better low modes with dynamic PWM

[thefreeman]

@Kakapo

Would this by any chance be able to get PWM FET dimming working on a Lume1? From what I understand the reason it was disabled is because the PWM frequency used by the 10-bit buck/boost channel didn’t work well for the FET channel (too low) and generated audible noise.

It would be a pretty huge upgrade for Lume1 drivers if it could

That’s one reason but there is also the issue with the FET-BB transition. With linear drivers when the FETs turns on it’s in addition to the linear channel(s), at the transition the FET starts at 0% then progress to 100% as we ramp up, therefore it ramps up smoothly without any jump in brightness.

With the lume1 it’s either BB or FET, the FET channel would need to start where the BB left the current to, which is 3A, except, we don’t know what FET PWM level corresponds to 3A since it varies with Vf, cell’s state of charge and internal resistance of the circuit. You might have to estimate some minium FET PWM level that sort of work without having the output increase* when you ramp down to BB, it’ll probably need a big margin of error and you’ll still get a large jump between BB and FET when cell’s SOC is high.

Edit : * Actually, this already happens since the BB output is higher than the FET at 100% at low SOC.
Even with a buck converter like in the Fireflies Lume1 driver, at some point 100% FET ≈ 100% buck, but when the cell is full, 100% buck ≈ 25% FET. If the transition level is lower than 100% then the brightness will jump up when ramping down at some SOC.

[Kakapo]

@thefreeman

@Kakapo

Would this by any chance be able to get PWM FET dimming working on a Lume1? From what I understand the reason it was disabled is because the PWM frequency used by the 10-bit buck/boost channel didn’t work well for the FET channel (too low) and generated audible noise.

It would be a pretty huge upgrade for Lume1 drivers if it could

That’s one reason but there is also the issue with the FET-BB transition. With linear drivers when the FETs turns on it’s in addition to the linear channel(s), at the transition the FET starts at 0% then progress to 100% as we ramp up, therefore it ramps up smoothly without any jump in brightness.

With the lume1 it’s either BB or FET, the FET channel would need to start where the BB left the current to, which is 3A, except, we don’t know what FET PWM level corresponds to 3A since it varies with Vf, cell’s state of charge and internal resistance of the circuit. You might have to estimate some minium FET PWM level that sort of work without having the output increase* when you ramp down to BB, it’ll probably need a big margin of error and you’ll still get a large jump between BB and FET when cell’s SOC is high.

Edit : * Actually, this already happens since the BB output is higher than the FET at 100% at low SOC.
Even with a buck converter like in the Fireflies Lume1 driver, at some point 100% FET ≈ 100% buck, but when the cell is full, 100% buck ≈ 25% FET. If the transition level is lower than 100% then the brightness will jump up when ramping down at some SOC.

Right, I didn’t know Lume1 wasn’t able to drive both channels at once… Now I’m wondering if channel switching feature would be easy enough to implement. One channel being only buck-boost, and one channel being only FET.

You would have two seperate ramps, but it would be like having an efficient EDC light and a pure FET hot rod in one body.

[thefreeman]

I don’t see how channel switching would help. One thing I can think of is reading the cell voltage to change the transition level accordingly, it would still be approximative with a jump between the two channel, but at least it would have some amount of FET PWM dimming to help thermal throttling, however… that means recalculating the ramp on the fly, which isn’t something Anduril can do.

[Gnarliest_Gnome]

@ToyKeeper

@pol77

If the attiny85 can’t do what’s needed, then I guess the FWAA will never have lower lows

I really don’t know what the deal is with FWAA. I’ve heard it runs fw3a-219 firmware, but I’ve also heard it’s a FET+1 driver, and … those two things aren’t compatible. It sounds like someone made a mistake, but I’m not sure who or what exactly the mistake was, because Lumintop didn’t provide the the source code they used. So it’s on my ever-growing list of license violations to clean up.

I can confirm that the FWAA uses the FW3A-219b fw. I don’t know what that means for the possibility of lower lows, but moonlight is disappointingly high on this light. A user made a proper config for the FWAA here that fixed an issue at top of ramp but didn’t touch the PWM.