Optimizing 105C driver AMC7135

Yeah scaru, but lets stay within realistic values for regular flashlights. :P

So are you suggesting that 3 amps is the best drive current even for something with a copper heatsink?

No. But there is something inbetween 3A and 5A. Talking about the usual hosts like P60, C8.. I'd say for limited use, 3.5A is the limit. For short "bursts", it might even be close to 4A.. but heat sag occurs rather fast. Most budget lights dont even have proper heatsinking so assuming a well built light with copper heatsink is a little unrealistic. :P

@Silicon: What I'm now telling you might be VERY wrong but it could also be more true than I expect it to be.. anyway, LEDs have a fordward voltage (Vf). They wont light up below that. Voltage determines the maximum current, so an XML wont pull 4A at 2.8V.. it might pull 6A at 4V but it doesnt have to. Thats where the AMC chips come in handy. They limit the current and also burn up some of the voltage but I dont really know if that matters..

You’re right, I don’t understand you. I don’t understand why you keep questioning the answers provided by people who understand the laws of physics. “Hmm, I don’t quite agree with the answers”

The key for an LED is I (Current) - Voltage is completely irrelevant. That is why, if you read the CREE datasheets, they will give you luminous intensity at a given current without even talking about voltage. An LED is an imperfect device - every single one of them is different, and this is why Vf in the datasheet is given as a “Typical” value and a “MAX” value, and they are pretty significantly different. A “MIN” isn’t even defined in the datasheet, because CREE doesn’t consider it a problem (and they’re right) if the Vf is lower than Typical. The “Goal” as you put it has NOTHING to do with 3.35V. With an LED, you either control current or you control voltage - the other value becomes what it needs to be all by itself. AMC7135s regulate current.

If it’s not as bright as your TN12, then any of these is possible:

  • Your TN12 is driven to higher than 3.4A (meaning there is nothing wrong with your driver)
  • Your TN12 has a much higher BIN Emitter than the one you’re working with (U2 compared to T4, for instance) (meaning there is nothing wrong with your driver)
  • Your TN12 has much better heat-sinking than whatever is currently heat-sinking your LED (meaning there is nothing wrong with your driver)
  • Your driver is broken and not actually supplying 3.4A
  • Your power source (battery?) can not provide 3.4A
  • Your power source (battery?) does not provide enough voltage for the LED to operate at 3.4A (measure your battery voltage while it’s running the LED)

If you can’t measure current, then you can not verify if a current regulator is working. To see if a current regulator is putting out its intended current, you’ll have to measure that value.

It depends on the heat-sinking of the LED and the efficiency of the optics. 700 Lumens OTF of an XM-L based flashlight is pretty normal.

Your being a newbie and having a lack of knowledge is no problem - there are lots of us here willing to help. That you continue to ignore the answers provided and replace fact with assumption and ill-knowledge is a bit more frustrating.

PPtk

I have just read some more docs about how do drive a led and I got it now.
Just relax, it is also frustrating for me to get answers like those :expressionless:
Subject is closed :o

“Never Mind” is the new Original Post? I wouldn’t count on getting a lot of help from the people here with that kind of attitude.

E1320, Dr Jones, willie, Vieplis, scaru, NightCrawl, and I all offered you answers, and you still continued to imply that our answers were wrong and that you needed to increase voltage but not current - which is impossible. If you’re uncomfortable being presented with answers that make sense, then I’m sorry about that.

Good luck with your mod.

PPtk

Dr. Jones (or anyone), could you maybe elaborate? I am getting some intermittent “flickering” (funny sounding word lol) with my SE-1 (Balder) and I pulled tail cap & it seems ok. The head is potted so can”t get at that. Bad tail cap switch? Chip? Any ideas? I need to find the prob before the send back window closes. Appreciate any help.

Keith (who don”t like no flickering)

Most likely either Bad Tail-Cap switch or cell isn’t being held tightly enough by spring tensions. Does it flicker if you set it down and let it lie still?

Is it in all modes or just med/low? Might be PWM.. or you should stop shaking the light. :P

My best guess is also what PPTK said.

If removing the tailcap and placing a piece of wire shorting out the tail cap does fix it then try making a small spacer to place in the battery tube. If that fixes it then you need a longer spring.

[quote=PilotPTK]

I”m thinking switch as well. Yes, it flickers when laying still. I have stretched spring already but will try & stretch a little more……….maybe add a magnetic spacer. Thanks. I”ll post findings.

Keith

Easy enough to diagnose, just short the battery -ve to the body and see if it still flickers. If it doesn't you've got a bad switch.

Not PMW. I just tried it and it is working perfect. But as I stated it is a intermittent issue.

Keith

Not sure I understand what you mean scaru with the wire/shorting. Could you describe? Now it is flickering again. DRATS! This is the lighthound version and I have the Balder version coming (any day now) at which time I shall try the tail cap from it. I also tried a magnetic spacer. Stretched spring, cleaned it good. Before hitting save I checked and it is working (this is how it does). Thanks guys.

Keith

Ok, what I was trying to say is first just use a piece of wire connecting battery to the host so as to rule out the switch. If that does fix it. Ie no flickering then it is the switch to figure out whether it is the spring or some internal part, you place a spacer in there so you can be sure the spring has good contact. If that fixes it you need a longer spring if it doesn’t then it is the switch. I hope that helps.

I understand. Tried spacer no worky. Just eliminated switch with paper clip and still no good. So it”s in the head then? If no other ideas then its RMA I guess. At least it is Lighthound I”m dealing with meaning no hassle quick turn around. I still hate it! Thanks scaru.

Keith

Yep, RMA Time. I’m very surprised that it’s not the tail…

The problem is sometimes it will do it all the time & then it “fixes” itself & will have to be left on for a few minutes or more till it starts flickering. You know how it goes………something does not work till you take it in then it works. I”m concerned they will turn it on & off a couple of times & say nothing is wrong. I am going to call LH & explain it in detail for them. It is working fine as I type (I mean peck). The one I have is the LH version with the head up clip. I also have one coming with the head down clip from IO (been 3 wk). If I had purchased this one from China, I would not even send it back. Before I sent this post I went outside with my dog & left the light on &…………….you guessed it, working perfect! Oh, the humanity! I love this little light & just hope this is not the down fall of this “budget” light. I am gonna hit send & its still working perfect. BTW, thanks all for trying to help. I just turned it off/on & yep…………it started flickering LMAO.

Keith

A quick video clip will explain everything, even if the light decided to be OK after returned.

When looking at data sheets, it’s very easy misunderstand things. I spend months trying to figure stuff out so that I can ask relevant questions and still I look stupid. For LED current vs voltage graphs a specific current drawn does not correspond to a precise voltage drop but an average of the type of led measured(more like guidelines). This why led drivers are current regulated. A small difference in voltage applied can result in a large difference in current drawn if a voltage regulator is used where if a current regulator is used, a small variation in current output of the driver remains a small variation. You cannot use voltage drop across the emmiter to guage output. It may not be meaningless, but it is irrelevant.
Did I pass the quiz?