Oh, nearly missed it; sure, you can put NLITE, luxdrv, MiniDrv and MiniMo into the repository. Good idea, thanks for managing the repository :)
Hi, I’ve been stalled due to other projects, but today I tested the output of this light at 700mA with a 16340 cell. The actual modes still need to be tweaked, but this at least gives me an idea of the range I can expect:
- Moon: 0.98 lm
- Low: 3.50 lm
- Med: 19.6 lm
- High: 75.5 lm
- Maximum: 173 lm
So, I’m actually getting more output than I expected — 173 lm instead of 142. And that’s after putting DC-Fix on both sides of the lens, using a battery which wasn’t fresh from the charger, so I suspect the output could be perhaps 15 or 20 lumens brighter in ideal conditions.
I’ll have to build a second host before I can tweak and test anything else though, since the first host’s MCU is extremely difficult to flash. I hope the second one will be easier.
Waiting for pics 
^^this
That’s pretty good output for a tail light. What is the Vf at the emitter for this? Just curious how hard the 7135’s are working at 700ma.
I haven’t tried to measure the Vf, but the data I found suggested it should be about 2.3V at 700mA.
Sorry for the delays… I still haven’t assembled the other two hosts so I don’t have pics yet or final firmware. I did fix my firmware flashing hardware though, so hopefully it’ll be easier to reflash now. And I got a chance to try it on the road… I don’t remember now whether I was using the first or second flasher (first, I think), but from about a third of a mile away it was about as visible as a car tail light… with plenty of room to get brighter if necessary.
As you guys know I have lots of color XP-E2’s in all sorts of different projects (using several different regulation methods and DD) and I’ve actually found the Vf to by a good amount higher than in DJOzz’s tests even at much lower currents. I haven’t measured specifically at 700mA but at 120mA I’m reading 2.6-2.8v over the emitter.
These are all DTP mounted and all from the same exact batch (ordered 30 of each color at once from digikey). My findings have been consistent threw 8 different lights, some running 7135’s, some running my dual transistor CC circuit and one DD (tho I obviously can’t measure that one at lower current levels).
When I was making the very first RGBW driver everyone was jumping on my telling me the red emitters couldn’t handle it and would die instantly, that is simply not the case, these things are amazingly resilient and can handle nearly the same voltage (and just as much current) as the B and W and even G ones can.
I have been following the data in these but something just isn’t adding up…
170 lumens at 700ma? 2,7Vf at 120ma? This doesn’t jive with the spec sheets or the graph:
It’s very possible that my cheap lux meter gives skewed results based on the tint. However, it does visually look like it’s about as bright as my ZL H51w, as much as a red light can resemble a white light.
I guess the only reason I have held off on the red emitter project is the status of the AMC7135’s in the loop. At lower currents, they will be working harder and the peak charge on the cells will give them a jolt. It almost makes more sense to attain the 700ma (RMS) using a high rate PWM and just removing the high mode (if that is the goal). This allows more 7135’s to manage the load and the efficiency should be increased significantly. Since most flash modes are 100% on, these too would want to be limited to the PWM settings for the 700ma max. I don’t know how hard this is to manage in coding.
In my world, a red bike tail light is comfortable at 1.0 amps (3x 7135) using aspheric lenses (wide beam angle). I would have no qualms with driving this with 4x 7135 and a 75% PWM. Anything to keep from wasting energy in the form of heat in the driver.
What I do welcome is runtime. Right now, at 1.05A NANJG 47-AK using the police mode (16 mode driver) I get 10 hours on a 3400mah cell. This is the most efficient flash mode I have. This is what I am interested in when it comes to bike lights; highly recognizable and efficient flash patterns based on a known output levels.
I dig runtime too. If my numbers are anywhere close to correct, I think I should get 30+ hours of tail lighting on a 550mAh 16340 battery. That’s using what is probably the brightest flasher mode I can without bothering people.
I’ll have to get actual measurements when the firmware is closer to finalized.
That would be some trick.
I cannot even get close to that with 3400mah 18650 at only 1.05A.
I was only getting 6 hrs in default strobe mode at 1.05A on XTAR 2600mah cells.
It’s been a while since I did the runtime tests, but the increase in cell capacity has helped.
If you are running the light at 700ma that equates to about 2.52 watt/hr; 0.7A x 3.6V*).
The cell capacity is 2.0 watt/hr for the 16340 cell (0.55A x 3.6V*) so that means you can only use a 6.7% duty cycle to achieve 30 hours.
A 6.7% duty cycle means you have about 4 minutes (240 seconds) of on-time per hour (ref: 60 min x 60 sec = 3600 sec/hr *.067 = 240 sec)
- I am using 3.6V as the average available voltage before driver fold-back warning.
Out of curiosity, is this line of thinking following your calculations?
So, if it’s running at 3.5 lm and flashing up to 19.6 lm once per second (5 brief flashes, very short), it’s running at 2.0% to 11.3% of its maximum power. It spends about 95% of its time on the lower level though, so the overall power draw is about 2.49%. Apply that to 700mA and I get 17.4 mA average. With a 550mAh cell, that gives me 31.5 hours of power.
3.5 lm is a bit high compared to most bike tail lights, and IIRC someone said 20lm is obnoxiously bright. So, those two seem like good level choices if it only pulses briefly at the “obnoxiously bright” level.
For now I’ve only got guesses instead of actual tailcap measurements… But I suspect the guesses are at least within a factor of 2, which satisfies my intent to give it a minimum runtime of 15 hours on a useful level.
Understood. I can’t quite follow the math but the limited output makes this more logical.
My goal is daytime output where you compete with sunlight and dropping into the shadows.
Annoying is very much related to LUX rather than lumens. Superflash lights for instance are seriously annoying but only when you are in just the right spot. Change the angle by a few degrees and these little monsters disappear in daylight. Given that they are white light, you get the full force of an aligned TIR from a 2 watt flash. Point is simply how you are planning to lens the light.
I have done the 1x 7135 constant on and add 2x 7135 strobe. In daytime, this nearly made the flash disappear. But at night, it made the light much more tolerable. One of my favorite P60 does this for a night time helmet light.
I am looking forward to seeing exactly what your signal looks like. I think I get it but I am not sure. I guess I got lost where you are applying the 700ma other than calculating the duty cycle (2% and 11.3%).
Nightspy- since you called me out I went ahead and set up a more precise little test. The other times I tested at 120mA it was by ramping one of my built lights down to a lower level (therefore lower PWM). This time I built a constant current source (read NON PWM) and set it to ~200mA (by the math, actual measured output was 221mA) I didn’t have the right resistor values to set it at 120mA.
I mounted the emitter on a Noctigon and screwed that to a 2# block of 6061. Measuring the voltage over the emitter after 30sec (the CC circuit was powered by a constant 5v source) I measures 2.835Vf.
Before doing the test I allowed the emitter to run 2 hours total at 2A (in 30min increments with 5 minute rests to allow the heatsink to cool) to do a burn in. Perhaps that’s the source of the difference between my test and the graph but I can 100% assure you I know my shit and I know how to take simple (but accurate) voltage and current measurements.
Thanks CK. I didn’t mean to call you out; just trying to wrap my head around the data. I certainly know you know your stuff.
This just throws my development numbers in relation to specs out the window… which as a designer is maddening 
Page 9 here says the current should be going through the roof at 2.8V
http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXPE.pdf
Now I’m going to have to write Cree!
Seriously, thanks for confirming the real-time readings.
edit: I guess I should add XP-E2 specs… page 8 still has a huge disparity specifically for the red emitter.
http://www.cree.com/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXPE2.pdf
As long as the emitters are on good copper stars and thermal management is adequate, you can easily push the emitters beyond the specs shown on data sheets, guys here routinely hotrod them w/o issue…albeit the heat produced goes up faster than lumen output, unfortunately, once you get past the spec sheet data of course 
I understand that, Warhawk, but the discrepancy here is the Vf at a lower current. According to Cree, the Vf is only 2.65V for a 1A draw. At 350ma, the Vf should only be 2.2V. The only logic for why an XR-E2 red emitter would run at 2.835V at only 200ma is that a 2A break-in period fundamentally changes the specification of the emitter.
I also noted that MTN Electronics sanctions (loosely stated here) 1.9A on a Noctigon with adequate heat-sinking. Again, I am not questioning the findings. Awareness here definitely deserves more study on my part. And trust me, Cree will be in the loop to get to the bottom of this. To date, I have not seen such a huge discrepancy in their product line.
I had to go look at the source code again, but what I’m using now is:
- Bright for 5ms, then dim for 65ms.
- Repeat the above 3 times (4 blinks total).
- Dim for 720ms.
- Repeat the whole process at a rate of once per second.
So, it’s bright for 20ms total and dim for 980ms, meaning the duty cycle is actually (0.02 * bright) + (0.98 * dim). Both are using PWM at 19 kHz, so a 5ms bright flash is actually 95 individual pulses (0.005 * 19000) at a speed too fast to perceive.
On my S7-219B, I find this sort of flasher works well as a handlebar light, alternating between levels 3 and 5 (med and max, 42lm and 342lm). Those modes run at 187mA and ~1800mA, resulting in an overall draw of 219mA ((0.98 * 187) + (0.02 * 1800)). With a 3100mAh cell, that gives me just over 14 hours of run time on a mode which is extremely visible. My alternative would be to run on mode 4 all the time (155 lm, 745mA), which would give me a bit over 4 hours of run time.
The main difference for the tail light is that it’s red, pointed backward, and running at lower levels. Plus, it has even more diffuser film to make the beam wider.
What is the rise time of each pulse? I’m guessing you are not reaching full output in the 5ms bright modes with this high frequency rate (19kHz)?
Rise time is one of the variable difficult to account for in the runtime equation. It actually increases runtime but lowers output if clipped.
I can see how the S7-219B remains distinctive. My brightness ratio was closer to 3/1 which washed out the flash too much. You have a near 9/1 ratio. 14 hours is still an impressive runtime!
I will have to retest my police mode against a 3100ma cell (or new 3400mah cell since all my 3100’s are well used). I have a 1.4A and a 1.05A XM-L light I can test. The frequency of the police mode is 5 fast flashes per second (approx.) and no reduced on-time.