*BLF LT1 Lantern Project* (codes going out for more LT1s, second batch shipping!)

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Phlogiston
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Stereodude wrote:
DBSAR wrote:
yep, 1S4P as the same configuration for the Q8, which in this case with the lower maximum amp draws it can run on even one 18650 or four.
It’s not constant current regulated. It’s regulated (by throwing away excess voltage/power) until the battery voltage drops below Vf + the Rdson * current. At which point it is no longer regulated.

This lantern is crying out for a boost drivers and series strings of 4 LEDs.

Actually, I prefer the linear driver for this project. That way, the lantern is less likely to suddenly die on me when the cells run low, as often happens with boost drivers.

The linear driver can just drop out of regulation and gradually lose output, whilst still producing enough light for me to find my spare cells and another light to use while I change them.

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Phlogiston wrote:
Stereodude wrote:
DBSAR wrote:
yep, 1S4P as the same configuration for the Q8, which in this case with the lower maximum amp draws it can run on even one 18650 or four.
It’s not constant current regulated. It’s regulated (by throwing away excess voltage/power) until the battery voltage drops below Vf + the Rdson * current. At which point it is no longer regulated.

This lantern is crying out for a boost drivers and series strings of 4 LEDs.

Actually, I prefer the linear driver for this project. That way, the lantern is less likely to suddenly die on me when the cells run low, as often happens with boost drivers.

The linear driver can just drop out of regulation and gradually lose output, whilst still producing enough light for me to find my spare cells and another light to use while I change them.

That has nothing to do with ho boost drivers work. It just depends on how smart the U.I. of the light is. It should be no problem slowly reduce the brightness at the end of the runtime.

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Stereodude wrote:
I’ve yet to see anyone quantify the switching losses, so for all I know someone is chasing a sub 1% gain.
This. And given the tendency of Chinese manufacturers to play the part swap game, there’s something to be said about a proven reliable design where few things can go wrong. I like a nice driver as much as anyone but I like a working light even more.
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Stereodude wrote:
The_Driver wrote:
The FET based linear driver is more efficient in all modes except the max mode because the LEDs are actually being driven at a lower current. LEDs become much more efficient with less current. A 7135 based driver always drives LEDs at the set current, so they have identical effeiciency in all modes.
Theoretically yes. Maybe… You’re only saving switching losses. Nearly all the losses or gains in efficiency at varying current levels are due to heating of the die. The die heating at 175mA vs. 350mA with a 50% duty and a reasonably fast PWM will be virtually identical meaning there is no efficiency loss/gain in the LED itself. It’s only the switching losses of the PWM.

I’ve yet to see anyone quantify the switching losses, so for all I know someone is chasing a sub 1% gain.

Can you prove this? I don’t believe it. LEDs have a lower forward voltage at lower current levels. This means that the total power consumed is less (instead the power is burned off in the FET, which is not a problem when cooled properly). Also, the reason that LEDs get dimmer with higher current density is not actually heat. You can cool an LED to negative temps and it will still become less efficient at higher current levels. This effect is called droop. Of course heat is an additional problem that can further reduce brightness. The LED will definitely be cooler with the FET because it runs at lower power. In addition to this it’s also brighter…

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The_Driver wrote:
Phlogiston wrote:
Stereodude wrote:
This lantern is crying out for a boost drivers and series strings of 4 LEDs.

Actually, I prefer the linear driver for this project. That way, the lantern is less likely to suddenly die on me when the cells run low, as often happens with boost drivers.

The linear driver can just drop out of regulation and gradually lose output, whilst still producing enough light for me to find my spare cells and another light to use while I change them.

That has nothing to do with ho boost drivers work. It just depends on how smart the U.I. of the light is. It should be no problem slowly reduce the brightness at the end of the runtime.

Fair enough, but someone has to specifically implement that in the boost driver, whereas a linear driver just works that way with no extra effort.

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The_Driver wrote:
Stereodude wrote:
The_Driver wrote:
The FET based linear driver is more efficient in all modes except the max mode because the LEDs are actually being driven at a lower current. LEDs become much more efficient with less current. A 7135 based driver always drives LEDs at the set current, so they have identical effeiciency in all modes.
Theoretically yes. Maybe… You’re only saving switching losses. Nearly all the losses or gains in efficiency at varying current levels are due to heating of the die. The die heating at 175mA vs. 350mA with a 50% duty and a reasonably fast PWM will be virtually identical meaning there is no efficiency loss/gain in the LED itself. It’s only the switching losses of the PWM.

I’ve yet to see anyone quantify the switching losses, so for all I know someone is chasing a sub 1% gain.

Can you prove this? I don’t believe it. LEDs have a lower forward voltage at lower current levels. This means that the total power consumed is less (instead the power is burned off in the FET, which is not a problem when cooled properly). Also, the reason that LEDs get dimmer with higher current density is not actually heat. You can cool an LED to negative temps and it will still become less efficient at higher current levels. This effect is called droop. Of course heat is an additional problem that can further reduce brightness. The LED will definitely be cooler with the FET because it runs at lower power. In addition to this it’s also brighter…


I was going to answer similarly but The_Driver beat me to it! If you want to know about the rated difference in efficiency at the LED itself, simply look at the LED datasheet and find the current over Vf curve. For CREE LEDs it’s even easier. Just check out the CREE PCT here and input any LED from their list, and they show you the voltage, wattage, lumens output, and overall efficiency (lm/w) of the LED at various current levels. Every part of the lighting system will have its own efficiency calculation. It isn’t just at the FET, nor is it only from heat.

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The_Driver wrote:
That has nothing to do with ho boost drivers work. It just depends on how smart the U.I. of the light is. It should be no problem slowly reduce the brightness at the end of the runtime.
Why do we want it to dim? How about some sort of flashing indicator or a brief flash of the lantern itself (like once a minute)?

The_Driver wrote:
Can you prove this? I don’t believe it. LEDs have a lower forward voltage at lower current levels. This means that the total power consumed is less (instead the power is burned off in the FET, which is not a problem when cooled properly). Also, the reason that LEDs get dimmer with higher current density is not actually heat. You can cool an LED to negative temps and it will still become less efficient at higher current levels. This effect is called droop. Of course heat is an additional problem that can further reduce brightness. The LED will definitely be cooler with the FET because it runs at lower power. In addition to this it’s also brighter…
Again, can you quantify the gain? Most of the power gain you’re claiming is irrelevant because it’s not a system level gain. A small amount of the power is just burned off in the FET instead of the LED. The system efficiency is not improved from a battery run time perspective. You’re just moving the heat around. With a boost driver you could actually save on input power and gain system level efficiency with the lower Vf.

Frankly, I don’t care much about a linear FET vs. 7135s. Both are bad solutions. The right solution is a true constant current boost driver.

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I’m interested in thus. Are we still able to sign up?

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Twinnie wrote:
I’m interested in thus. Are we still able to sign up?

Added Twinnie to the interest list at number 964. Welcome to BLF!

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One thing I would like to make sure ends up in the final design is a solid method of hanging and carrying the lantern. Keep in mind the added force of momentum when walking with the weight of 4× 18650s and the battery compartment swinging and bouncing around.

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Stereodude wrote:
The_Driver wrote:
That has nothing to do with ho boost drivers work. It just depends on how smart the U.I. of the light is. It should be no problem slowly reduce the brightness at the end of the runtime.
Why do we want it to dim? How about some sort of flashing indicator or a brief flash of the lantern itself (like once a minute)?

I understand both sides of the argument. A setting in the U.I. would make everybody happy. In my eyes a lighted switch with multiple colors is the better solution to warn the user. If they want to they can then reduce the brightness.

Stereodude wrote:
The_Driver wrote:
Can you prove this? I don’t believe it. LEDs have a lower forward voltage at lower current levels. This means that the total power consumed is less (instead the power is burned off in the FET, which is not a problem when cooled properly). Also, the reason that LEDs get dimmer with higher current density is not actually heat. You can cool an LED to negative temps and it will still become less efficient at higher current levels. This effect is called droop. Of course heat is an additional problem that can further reduce brightness. The LED will definitely be cooler with the FET because it runs at lower power. In addition to this it’s also brighter…
Again, can you quantify the gain? Most of the power gain you’re claiming is irrelevant because it’s not a system level gain. A small amount of the power is just burned off in the FET instead of the LED. The system efficiency is not improved from a battery run time perspective. You’re just moving the heat around. With a boost driver you could actually save on input power and gain system level efficiency with the lower Vf.

Frankly, I don’t care much about a linear FET vs. 7135s. Both are bad solutions. The right solution is a true constant current boost driver.

Sure:
Lets say you are driving a Cree XPL HD 3000K 90CRI (very similar to Samsung LH351D) in bin U3 at 2A and 50°C with a 7135-based driver. You will get 588lm at 91.2lm/W (efficiency for just the LED, together with the driver it’s lower). Now you want to dim to 50% of this current. The LED will thus still be running at 2A, but with PWM. So you will basically double the battery runtime with half the brightness (294lm) at the same LED efficiency of 91.lm/W.

With FET-based linear driver the LED would have the same brightness and efficiency at 2A, but at 1A it would be brighter and thus more efficient (see here). The above XP-L produces 330.5lm at 1A (109.9lm/W). Thats 12% more brightness for free. A fet-based linear driver is cheap just like a 7135-based one.

Both drivers are running at the same total power (depends on the current pulled from the battery and is independent of the LED). The difference becomes more prononouned as the maximum current the driver needs to be capapable of is increased and especially of you like to use low modes.

At 350mA and 30°C the above XP-L LED has an efficiency of 130.6/lm/W. Thats already 45% higher compared to the the same LED when PWMed at 2A and you can of course lower the current even more.

Of course a boost driver is the better solution from a technical standpoint, but if we are set on a linear driver we might as well use the better kind.

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I’m way less impressed with a driver that improves efficiency (so runtime) with 10%, than I am with good quality light coming out of the lantern and a good user interface. I feel the pain that a lineair driver (whatever kind it will be) burns off some precious battery power as heat, but in actual use (the BLF lantern is very much intended to be a practical light) that will not matter very much I think (set it at 10% lower output and you got your runtime back).

There was a similar discussion about the D4 having a primitive and wasteful driver, while what I notice in reality is a impressively functioning flashlight with a wonderfully intuitive user interface.

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The_Driver wrote:
Sure:
Lets say you are driving a Cree XPL HD 3000K 90CRI (very similar to Samsung LH351D) in bin U3 at 2A and 50°C with a 7135-based driver. You will get 588lm at 91.2lm/W (efficiency for just the LED, together with the driver it’s lower). Now you want to dim to 50% of this current. The LED will thus still be running at 2A, but with PWM. So you will basically double the battery runtime with half the brightness (294lm) at the same LED efficiency of 91.lm/W.

With FET-based linear driver the LED would have the same brightness and efficiency at 2A, but at 1A it would be brighter and thus more efficient (see here). The above XP-L produces 330.5lm at 1A (109.9lm/W). Thats 12% more brightness for free. A fet-based linear driver is cheap just like a 7135-based one.

Both drivers are running at the same total power (depends on the current pulled from the battery and is independent of the LED). The difference becomes more prononouned as the maximum current the driver needs to be capapable of is increased and especially of you like to use low modes.

Your numbers are misleading with these linear driver topologies. Those are LED watts, not watts pulled from the battery.

If we look at watts pulled from the battery, the reduction in Vf doesn’t help. So, that 109.9lm/W is really only equivalent to 102.5lm/W. Further, your system efficiency is bad. Vf is 3.01V at 1A which means with a fully charged battery you’re throwing away >25% of the batteries power.

Quote:
At 350mA and 30°C the above XP-L LED has an efficiency of 130.6/lm/W. Thats already 45% higher compared to the the same LED when PWMed at 2A and you can of course lower the current even more.
Who is going to be PWM’ing at 2A? This lantern is supposed to have 4 LEDs of each color and something around 1000lm output. That means the LEDs are going to be driven at about 1A on high at the two color temp extremes.

Quote:
Of course a boost driver is the better solution from a technical standpoint, but if we are set on a linear driver we might as well use the better kind.

Why are we set on a linear driver? A good boost circuit should be able to achieve >90% efficiency. A linear driver achieves way less than that. If we’re using four Sanyo 3500mA GA cells the battery will have an average voltage of about 4V over the first 1/3rd of it’s capacity. With Vf of 3.01V at 1A you’re just at ~75% efficiency with the FET driver. If you want to run it at 1/2 power (.5A) Vf drops to 2.87V and pushing your efficiency down to 71.75% efficiency. At 1/4 power Vf is below 2.82V and your efficiency is barely scraping 70%.

Pretending we’re using 4 of the Cree U3 bin LEDs at 50C like your example and we’re considering the first 1/3rd of the battery’s capacity WITH 4 Sanyo GA’s which have an average voltage of ~4V with a linear FET driver.

Full power (1A) gives 1322lm with a power draw of 16W from the batteries. That’s 82.63lm/W
Half power (.5A) gives 703.6lm with a power draw of 8W from the batteries. That’s 87.95lm/W
~Third power (.35A) gives you 502.8lm with a power draw of 5.6W from the batteries. That’s 89.79lm/W.

Now lets repeat the exercise with a 90% efficient constant current driver that uses PWM.

Full power (1A) gives 1322lm with a power draw of 13.37W from the batteries. That’s 98.88lm/W
703.6lm requires a power draw of 7.12W from the batteries. That’s still 98.88lm/W
502.8lm requires a power draw of 5.09W from the batteries. That’s still 98.88lm/W

If you have a constant current boost driver that can change the drive current (not PWM) the situation gets even better.

Full power (1A) gives 1322lm with a power draw of 13.37W from the batteries. That’s 98.88lm/W
703.6lm requires a power draw of 6.37W from the batteries. That’s 110.46lm/W
502.8lm requires a power draw of 4.39W from the batteries. That’s 114.53lm/W

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djozz wrote:
There was a similar discussion about the D4 having a primitive and wasteful driver, while what I notice in reality is a impressively functioning flashlight with a wonderfully intuitive user interface.
It’s different with a single cell flashlight. There you need a buck/boost driver and they’re not nearly as efficient as a pure boost or pure buck. That’s mid 80’s vs. low 90’s. Here’s a pure boost can easily be realized. Also, the LEDs are not being driven nearly as hard so Vf is lower and the linear driver is even less efficient. Further, I don’t understand your linking of the tint and UI with the driver. The tint isn’t going to change by using a boost driver nor the UI. You can have your cake and eat it too. And it’s not 10%. It’s almost 30% across the first 3rd of the battery capacity with a current adjustable boost driver that’s only 90% efficient at ~1/3 power. The gap will only widen more and more the lower the brightness is.
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Lexel has created the plans for the BLF Lantern in two types, the AMC-7135 version, and the other as a regulated FET version. I am not as experience with driver designs for future modding, but what is everyone’s vote on the driver for that ability? the AMC one (as AMC chips can be either removed or added for increasing the overall output & amps, or the FET one, (which i am assuming requires a resistor swap for a different ohm value to change the maximum amp & output?

AMC version:

FET version:

That Canadian flashlight guy & Lantern Guru -Den / DBSARlight

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Since this is a lantern, I vote for the FET linear driver.

My very own high current Beryllium Copper springs Gen 3:
http://budgetlightforum.com/node/67401
Liitokala Aliexpress Stores Battery Fraud: http://budgetlightforum.com/node/60547

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Just to fully capture the differences between the two drivers pictured above (and we are only talking about these two for the moment).

FET driver provides PWM free light, at the expense of the button LED. This assumes no change from the ATTiny85 to a different part.
AMC driver uses PWM and is likely less efficient, but retains the button LED function.

Since Lexel added programming pads for the MCU, changing that to a more capable part than the ATTiny85 could be in play, Lexel suggested considering the ATTiny84 IIRC.

Not sure if there is a significant cost change with any of these options, I suspect it is <$5.

I realize this temporarily ignores the boost driver discussion, no offense intended.

Given the choice between the FET and AMC driver, I vote FET driver.

BTW Lexel, thanks again so much for taking over the driver responsibility, regardless of the choice BLF will end up with a much better product. Wish we had connected sooner. Beer

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sbslider wrote:
Just to fully capture the differences between the two drivers pictured above (and we are only talking about these two for the moment).

FET driver provides PWM free light, at the expense of the button LED. This assumes no change from the ATTiny85 to a different part.
AMC driver uses PWM and is likely less efficient, but retains the button LED function.

Since Lexel added programming pads for the MCU, changing that to a more capable part than the ATTiny85 could be in play, Lexel suggested considering the ATTiny84 IIRC.

Not sure if there is a significant cost change with any of these options, I suspect it is <$5.

I realize this temporarily ignores the boost driver discussion, no offense intended.

Given the choice between the FET and AMC driver, I vote FET driver.

BTW Lexel, thanks again so much for taking over the driver responsibility, regardless of the choice BLF will end up with a much better product. Wish we had connected sooner. Beer

I do like the idea of a button LED, and with the FET version we could go with a simple resistored low-power yellow or amber LED to keep the button glow night light as i did when i built the BLF Steam pipe light glow tube. (using a 12K to 15K 1/8w resistor and a low forward-voltage LED will glow for years on the four 18650s. (loosening the battery tube a 1/4 turn like the Q8 to lock it out would turn off the glow button LED when in storage for long periods of time.

I’m not keen on a boost driver design for reasons in this case as mentioned earlier, and would just add more time to start over from cratch again. Lexel’s designs above gets my vote & approval for the lantern project.

That Canadian flashlight guy & Lantern Guru -Den / DBSARlight

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Please sign me up for 3. Looking forward to it all coming together into final form!

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Sign me up.

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quijibo wrote:
Please sign me up for 3. Looking forward to it all coming together into final form!

quijibo gets interest list numbers 965, 966, and 967.

wigglybroom wrote:
Sign me up.

wigglybroom gets interest list number 968, and a hearty welcome to BLF Beer

This may be my last post regarding additions to the interest list, as huey18 is writing some code to automate this, so I may be totally out of a job on this project. Crying Silly

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I vote for fet. Boost or buck would be more efficient, but costlier. And with 4 cells it will run forever for all my purposes.

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As we only have this options I also vote for the FET driver, but I would go with a more efficient (boost) driver all day even if it would cost a little more. Maybe Lexel could design one and sell it separately to modders.

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sbslider wrote:
DBSAR wrote:
if we can get the tint ramping feature integrated.
There is no doubt in my mind that Toykeeper is fully capable of this. The hardware is easy (and done), the firmware is not much different than what already exists in Anduril.

I already have most of the code written. I just haven’t been able to actually try it since the hardware doesn’t exist yet.

The light operates the same as any other Anduril light, but with one key difference: While the light is on, in almost any mode, the user can “click, click, hold” to make it change tint. This happens smoothly without significantly affecting total lumen output. If the color changes in the wrong direction, let go of the button and do it again.

djozz wrote:
I think it is too much to ask for Sofirn, but if you never ask for it you will certainly not get it: Could you ask for the 2700K led for one of the colour-bins W1 to W8, and for the 5000K leds for colour-bins R1 or R2? These Samsung tint bins are on or below the black body line, if Sofirn was able to source them (in 90 CRI of course) that would be awesome for the tint of the Lantern.

+1

I’ve been testing some LH351D emitters and I ended up with green ones. For the lantern, it’d be good to make sure we get something at or below the blackbody line if possible.

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Stereodude wrote:
djozz wrote:
There was a similar discussion about the D4 having a primitive and wasteful driver, while what I notice in reality is a impressively functioning flashlight with a wonderfully intuitive user interface.
It’s different with a single cell flashlight. There you need a buck/boost driver and they’re not nearly as efficient as a pure boost or pure buck. That’s mid 80’s vs. low 90’s. Here’s a pure boost can easily be realized. Also, the LEDs are not being driven nearly as hard so Vf is lower and the linear driver is even less efficient. Further, I don’t understand your linking of the tint and UI with the driver. The tint isn’t going to change by using a boost driver nor the UI. You can have your cake and eat it too. And it’s not 10%. It’s almost 30% across the first 3rd of the battery capacity with a current adjustable boost driver that’s only 90% efficient at ~1/3 power. The gap will only widen more and more the lower the brightness is.

I linked the tint and UI to this discussion just to give perspective how unimportant I think it is which actual driver is inside if in reality you do not notice it anyway, unlike tint or UI which are obvious in practice. You will not easily notice a 10% longer runtime.

But a 30% efficiency gain is something that I agree is worth trying to get, that is something that you do notice on the outside.

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DBSAR wrote:
Lexel has created the plans for the BLF Lantern in two types, the AMC-7135 version, and the other as a regulated FET version. I am not as experience with driver designs for future modding, but what is everyone’s vote on the driver for that ability? the AMC one (as AMC chips can be either removed or added for increasing the overall output & amps, or the FET one, (which i am assuming requires a resistor swap for a different ohm value to change the maximum amp & output?

Some thoughts on this…

Advantages to PWM / AMC7135 chips:

  • Better tint. LEDs get less white at low power, and these are expected to run at fairly low current. PWM runs at a consistent power level and produces a consistent tint regardless of how many lumens are coming out, but a constant current driver has more visible tint shift when not running at full power.
  • Can keep the button LED. PWM doesn’t require as many MCU pins, so we could still have a lighted button with multiple modes. The linear FET option may also have higher parasitic drain in standby mode, due to needing a voltage divider to measure battery status. This effect could be very small though, if done right.
  • Manages heat better. The 7135 chips spread heat across a wider area and have thermal regulation built in, so they don’t overheat. However, a linear FET concentrates heat into a smaller space on the driver, which means the driver itself may need heat sinking.
  • Better low modes, usually. The “raptor claw” 7135 chips have good performance in low modes, so the bottom of the ramp should be pretty low and pretty stable. However, a linear FET tends to have difficulty in really low modes, so the bottom of the ramp might not be very low or very stable.
  • Simpler driver design, easy and pretty much risk-free.

Advantages of a linear FET:

  • Higher efficiency in most modes. More lumens or more runtime. At the lantern’s power level though, this effect may be small, like only a 5% or 10% difference.
  • The parts might cost less.
  • Can potentially be modded for higher current by changing a sense resistor, but this also increases the risk of driver damage due to heat.

I’ll get things working on whichever one is used, but personally I lean a bit toward the simpler option even if it’s a bit less efficient.

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Thanks for your thoughts TK, and what if a boost driver would be developed, can that still have all the features of a 7135 driver?

Lexel
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ToyKeeper wrote:
sbslider wrote:
DBSAR wrote:
if we can get the tint ramping feature integrated.
There is no doubt in my mind that Toykeeper is fully capable of this. The hardware is easy (and done), the firmware is not much different than what already exists in Anduril.

I already have most of the code written. I just haven’t been able to actually try it since the hardware doesn’t exist yet.

The light operates the same as any other Anduril light, but with one key difference: While the light is on, in almost any mode, the user can “click, click, hold” to make it change tint. This happens smoothly without significantly affecting total lumen output. If the color changes in the wrong direction, let go of the button and do it again.

djozz wrote:
I think it is too much to ask for Sofirn, but if you never ask for it you will certainly not get it: Could you ask for the 2700K led for one of the colour-bins W1 to W8, and for the 5000K leds for colour-bins R1 or R2? These Samsung tint bins are on or below the black body line, if Sofirn was able to source them (in 90 CRI of course) that would be awesome for the tint of the Lantern.

+1

I’ve been testing some LH351D emitters and I ended up with green ones. For the lantern, it’d be good to make sure we get something at or below the blackbody line if possible.

lets go with the FET, most people dont care about 10% average efficiency gain for a more compley and costly boost driver

pinout
PB0 enable of Boost USB and the opamps
PB1 3000k
PB2 voltage divider 220/47k for LVP
PB3 switch over 1k
PB4 5000K

Madtoffel
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If we need the 7135 chips for the button LED and the FET struggles with low currents why don’t we just use a combined FET+1 design?

ToyKeeper
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Stereodude wrote:
The tint isn’t going to change by using a boost driver

Well actually… Silly

* GD&R *

Tint changes with current, and is usually best (whitest) when the current is in the medium-high range of an emitter’s power capacity. Tint is generally worst at very low power levels, or when the emitter is heavily overdriven, but fine anywhere in-between.

Here’s a video of a single emitter changing color due to different power levels being used. The light on the right is alternating between 350mA constant current and 350mA via a pulsed FET. The light on the left is only there for reference. http://toykeeper.net/torches/blf-a6/tintshift.avi (sorry for the bad video, I should re-do this demo sometime)

For the lantern, the risk is using too little power, causing unnecessary tint shift because the emitters aren’t running hot enough to get to their ideal range. If it’s only 1.4A total, split across 4 to 8 emitters, that’s 175 to 350 mA per emitter at the highest brightness. This is low enough to get some tint shift, but not a lot. However, a constant current driver will get worse tint shift as the total power goes down, while a PWM driver keeps a constant tint.

But between a linear FET or a buck/boost driver, tint shouldn’t be any different. They both shift the same way at low levels. The only style which doesn’t is PWM.

At least the effect doesn’t seem particularly bad on the LH351D. I notice it a lot more with XP-G2.

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