XM-L dedomed by accident (really...)

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lagman
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Well, here is what I think.
If you look at the graphs I posted earlier, you can see that at 3A the LED doesn’t output twice as many lumen as at 1.5A.
I suppose that if you have a 50% PWM signal you get half the lumen.
So in my opinion 3A with a 50% PWM outputs less lumen than 1.5A continuous…
But then again, I may be wrong about that. I never tested that.
Anybody else has an opinion on that subject?

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wight
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I suspect that you have it right. I’m just not 100% today, so I got it backwards earlier. Your logic is sound.

One thing that has been discussed but never implemented (on a publicly available driver) is having independently addressable 7135’s. This could eliminate PWM in the majority of situations, reduce the drop-out voltage, and make the light more efficient.

On the ATtiny13A microcontroller we often use for custom drivers there are 8 pins. Two are consumed for electrical connections (GND / BAT+). Another is consumed for battery monitoring. For an e-switch light yet another is consumed by the switch. That leaves 4 pins to work with, so to get modes with 12*7135 you’d do something like this: 1x, 2x, 3x, 6x.

Then your mode options would look like this:
12x (6x, 3x, 2x, 1x) - 100%
11x (6x, 3x, 2x) - 91%
10x (6x, 3x, 1x) - 83%
9x (6x, 3x) - 75%
8x (6x, 2x) - 67%
7x (6x, 1x) - 58%
6x (6x) - 50%
5x (3x, 2x) - 42%
4x (3x, 1x) - 33%
3x (3x) - 25%
2x (2x) - 17%
1x (1x) - 8%

For moonlight you’d still need PWM on the 1x.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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lagman
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That is a very interesting idea! And it would not cost much. It would just take a little bit more space to get the pins connected to each 7135 group.
I also wonder why nobody is doing drivers this way… Maybe because people wouldn’t notice the difference.
***
I think I will get a programming card soon… I would love to program a slow ramp up when the light is turned on to avoid being blinded. Also when changing modes. Man I love µcontrolers! Big Smile

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Rufusbduck
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Hi Lagman. What are you using to measure current? Many DMM’s come with thin probe wires unsuited for measuring high power led currents so many of us have had to change the probe wires to thicker ones to get more accurate readings. It was surprising to me how far off it can skew the readings.

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lagman
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Rufusbduck wrote:
Hi Lagman. What are you using to measure current? Many DMM’s come with thin probe wires unsuited for measuring high power led currents so many of us have had to change the probe wires to thicker ones to get more accurate readings. It was surprising to me how far off it can skew the readings.

Hi and thanks for your advice.
I did check the resistance of my probes. I have two DMM: Uni-T UT136B and Uni-T UT61E. The first has a resistance (probes plus DMM) of 190mohms and the second 120mohms approximately.
I realize that this is not negligible. At 3A that’s about 360mV drop. In my above posts I added 10% to my measurements to compensate for that but can you tell me if it’s more or less than that? I don’t know.

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Rufusbduck
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Only way I know is to go ahead and substitute thicker wires and see what the difference is. Your 10% is based on a resistance that might be off. In my case the inaccuracy was more than 10% at 3A and even worse at higher currents. 190omh x 3A means a drop of .57V. I wouldn’t call that insignificant when it’s very close to the difference between the voltage of the battery and the Vf of the led and could very easily result in a low current reading.

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lagman
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I totally agree with you. My 10% estimation was based on the fact that I can barely see a difference in light intensity. But it can be incorrect.
I have no way to test the real current right now… I’ll get a clamp meter at some point but not now.
BTW, do you know where to buy good quality banana (4mm) plugs? I want to make special probes for my DMM using silicon wires…

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

Tom E
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lagman wrote:
That is a very interesting idea! And it would not cost much. It would just take a little bit more space to get the pins connected to each 7135 group. I also wonder why nobody is doing drivers this way... Maybe because people wouldn't notice the difference. *** I think I will get a programming card soon... I would love to program a slow ramp up when the light is turned on to avoid being blinded. Also when changing modes. Man I love µcontrolers! :D

I think this is how PilotPtk's driver (ultimate 7135 driver) was supposed to function. Project went totally on the shelf months ago though I believe - trouble with parts.

wight
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Tom E wrote:

I think this is how PilotPtk’s driver (ultimate 7135 driver) was supposed to function. Project went totally on the shelf months ago though I believe – trouble with parts.


That’s correct Tom E, he ran into an errata vs supply problem IIRC. Here is his thread: The World’s Most Advanced AMC7135 * 8 Driver

He stated that his 7135’s were “individually addressable” which I find completely unnecessary for a single-color driver. (maybe he planned to do multi-color firmwares as well). He wanted to use a high-end MCU, USB, etc. His plan had many more barriers than doing this on a simple ATtiny13A. When he ran into errata problems that prevented USB from working he was put in a bind, IIRC there was not enough physical space for in-circuit programming of his MCU.

I think a firmware with a 2D lookup table could easily handle modes for X number of 7135’s. You’d configure 8* similarly to the way I showed in post #32 with 12*. Either way, you need 4 pins to address them in increments of one.
1x, 1x, 2x, 4x
8x (4x, 2x, 1x, 1x)
7x (4x, 2x, 1x)
6x (4x, 2x)
5x (4x, 1x)
4x (4x)
3x (2x, 1x)
2x (2x)
1x (1x)

As you can see, a different lookup table would be required for each driver which had a different total number of 7135s. Now that I think about it, maybe that is why PilotPTK wanted them individually addressable. Wink Oh well, writing a few lookup tables isn’t that bad.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

lagman
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I think that most people would not understand the advantage of such a driver. And IMO that’s why there is no driver like that… Sad
Developing such a driver would not be lucrative as only a few people would buy it.

My English isn’t perfect but I’m trying to improve it. If you see something that doesn’t sound right or is just plain wrong, please feel free to point it out! Smile

wight
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Several people here develop drivers without commercial gain in mind. http://budgetlightforum.com/node/29562

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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Tom E
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Well the advantage of turning ON/OFF 7135's is no PWM's. So 8 chips: high of 2.8A, 4 chips: 1.4A w/clean no PWM's, 2 chips: 0.7A w/clean no PWM's, 1 chip: 350 mA clean....

Also it's been discussed the nature of PWM's is toggling full power ON/OFF which has the same higher voltage demand as 100% power. So if you run with just 4 chips, the voltage demand is lower, therefore the cells will last longer, etc... All around more efficient, less stress... How much? Dunno, but theoretically much better - true direct amps, no PWM's - beautiful thing. I like the idea for sure...

wight
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Tom E wrote:

Well the advantage of turning ON/OFF 7135’s is no PWM’s. So 8 chips: high of 2.8A, 4 chips: 1.4A w/clean no PWM’s, 2 chips: 0.7A w/clean no PWM’s, 1 chip: 350 mA clean….


Also it’s been discussed the nature of PWM’s is toggling full power ON/OFF which has the same higher voltage demand as 100% power. So if you run with just 4 chips, the voltage demand is lower, therefore the cells will last longer, etc… All around more efficient, less stress… How much? Dunno, but theoretically much better – true direct amps, no PWM’s – beautiful thing. I like the idea for sure…

Don’t forget that you can still do PWM on a single 7135 as well, if you are so inclined. I think this will give a much lower moonlight than a stock qlite (for example) is capable of.

I guess somebody should get motivated to design the hardware. I’ve got a fair idea of how to handle the modifications to the STAR firmware as well.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

Tom E
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I think PPtk bit off too much - should have left off the whole USB thing... Probably much easier then.

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Unfortunately I have no time to tackle with eagle (not to mention programming) but this old idea should’t be too hard to become reality. Especially as OSH park can be used to fabricate pcb boards and parts of existing firmware(s) could be used. Most of us are by now more than capable to reflow few components and program attiny.

Society is like a pot full of nuts and bolts, finest pieces always end up on the bottom...

 

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