AMC7135 in series?

[ardo]

Could someone please confirm if two of these boards CANNOT be driven in series from two LiIon batteries?

I'm building a couple of lights for my camcorder, using 50Led bike lights from DX. I got 2 pairs of 2 LiIon cells from a laptop battery that should've given me 7.2V at 3800mAh. Batteries show 7.8V fully charged. I connected a single 50Led light using one of the 800mA controllers from DX:
3.6V~9V 800mA Regulated IC Circuit Board

I got decent light output for about 2Hrs and change, the voltage at the light was a solid 3.3-3.4V, but then it started dropping rather quickly, down to about 3V after 2.5Hrs, at which point I just turned it off. I guess I should've measured current instead... Anyway, with 2 lights (on two separate boards, of course) I'd get just over an hour of usable light, bummer... These ain't new batteries, so maybe that's the problem? I also noticed that the board gets quite hot.

The reason for 7.2V instead of a single 3.6V is that the 4.2V charger I have is only rated for 800mA, while my 8.4V camcorder charger is 1.5A.

So, if I can connect two AMC7135 in series, this may solve my problem of having to rig a new charger.

TIA - ardo.

P.S. Amazing forum, I wish I knew about it sooner!

 

[Gunner12]

Well, the two batteries are probably 3800 mAh in parallel and 1900 mAh in series. Each battery should be about 3.7v and 1900 mAh. I'm not if using two regulators in series will work. I don't think it would work. My 18650 charger charges at a even lower current, 500 mAh IIRC. I pop in a battery at night, go to sleep and in the morning the battery is charged.

Why 50 5mm LEDs? I understand if you already had that bike light. A single Cree P4(Q5 being the brightest right now) heat-sinked and driven at that current should produce more light(the bare emitter creates a pure flood beam pattern, if you use a reflector, like this one, more throw), smaller size, and better color rendition then 50 5mm LEDs.

Welcome to CPF!

 

[TigerhawkT3]

Nope, you can't drive electronic circuits in series. I tried that last year with MagLEDs, and they fried.

 

[ardo]

Thanks for your help. I did buy 2 50Led lights specifically for this project since I was under impression that most high-power leds are good for spot beam, not for flood. Obviously, I have a long way to learn... I'll go over stickies a few more times, but I'd appreciate if you could point me to a similar (i.e. lighting for video) project that you may have come across. Many thanks.

TigerhawkT3, thanks for the info on serial connections. You just saved me from frying any modules of my own.

 

[kenster]

7135

https://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=2958

 

[TorchBoy]

If you have that many volts under load, won't the lithium cells in parallel do the job very nicely with one triple-AMC7135 board?

As for 5mm vs Crees, the Crees are either total flood or tight spot. It doesn't seem to be easy finding anything in between, where the 5mm LED array is.

I will say, though, that the Crees make more light for the power than typical 5mm LEDs, especially in anywhere near affordable large arrays, so a Cree is still worth considering. One of the caving guys uses a simple reflector made of a cone of reflective plastic potato chip/crisp packet.

I use these optics to get a nice tight beam - much better beam than 5mm LEDs if you want distance. I'm toying with leaving out the optic itself and lining the empty optic holder with foil to get a wider beam.

 

[ardo]

Thanks, I think I'll get the 10-pack AMC7135 from DX, and try it with 3.6V in parallel, this should work better than my 800ma board at 7.2V, I think it does more heating than lighting at such a high voltage.

I smashed a couple of dead Par50 halogens and glued the lens to the front of the 50Led light. It fits pretty well and gives me a more uniform flood. I also put a 1/4CTO filter in front of the LEDs to correct their blue tint.

I still would like to try a Cree or an SSC, however, I'd have to make sure that I'm not blinding people with this thing. A ping-pong ball diffuser, maybe? It will probably melt... I'm not sure how a reflector would help, unless I turn the Cree towards the reflector.

As for 5mm vs Crees, the Crees are either total flood or tight spot. It doesn't seem to be easy finding anything in between, where the 5mm LED array is.

A 'total flood' sounds interesting, but how do I know which one I'm getting? Sorry, I'm a total noob...

I did forget one more thing: if I connect my LiIon batteries in parallel, won't l need a more powerful charger? I have a couple of 800mA chargers, could I wire those in parallel? Would a 1.6A charger work well charging 4 or 6 batteries? Many thanks - ardo.

 

[Gunner12]

...It will probably melt... I'm not sure how a reflector would help, unless I turn the Cree towards the reflector...
A 'total flood' sounds interesting, but how do I know which one I'm getting? ...

All Cree XR-E LEDs are the same in regards to emitting pattern. The different bins, P4, Q2, Q3, Q4, Q5, all signify the efficiency, with the Q5 being the best available.

A Cree has a very good flood without a reflector. Think of a smooth light without any spot at all, smoother then the 50 LED light you have now, and probably also better color rendering, though it might no throw as far as the 50 LED. The LED might be hard to stare into(all that light from a 1mm x 1mm square) but unless you are looking at the emitter, this should not be a problem.

With a reflector, the size of the spot and the amount of spill depends on the reflector. Something like the Tiablo reflector has the potential to project light 200 meters with a narrow beam while the Draco reflector will give you a smooth Surefire L4 like flood with a very wide beam and a "wall of light".

With good heat-sinking, the LED should not produce enough heat to melt plastic.

 

[TorchBoy]

I still would like to try a Cree or an SSC, however, I'd have to make sure that I'm not blinding people with this thing. A ping-pong ball diffuser, maybe? It will probably melt... I'm not sure how a reflector would help, unless I turn the Cree towards the reflector.

A 'total flood' sounds interesting, but how do I know which one I'm getting? Sorry, I'm a total noob...

Like Gunner12 indicated, they put out a lot of light from a very small area. A ping pong ball diffuser sounds like it could be a good idea, but perhaps a bit too opaque, too absorbant.

The LED doesn't put much heat out to the front but the base of the emitter and the star heatsink it's mounted on can get quite hot at higher currents.

"Total flood" may be the wrong way to describe it but the flood it provides is fantastic in certain situations, like as the boot light in my car (a station wagon), or for area lighting etc. For video work it would be too wide, as a lot of that light would be wasted out the sides, and video cameras only point in one direction. I'll have to try just putting a magnifying glass in front of one.

 

[Gunner12]

I'm thinking maybe the Draco Reflector for a good flood and a small size. That should give a "wall of light" according to the Draco beam-shots I've seen.

I'm not sure about the batteries and I don't think wiring chargers in parallel would be a good idea.

 

[ardo]

Guys, thanks so much for all your help!

Yesterday I tried to figure out how to charge my batteries. I have a 800mA 'smart' charger from an old Samsung phone. I opened up a matching battery, removed the protection board, and soldered it to a parallel pair of 18650s. The pack took over 5 Hrs to charge, but the charge time is not that critical to me.

Here's the question, though: I have 2 more of these Samsung batteries, so I could make 2 more packs with one protection board for 2 cells. Could I then have 3 pairs of 18650s charged by a single charger in parallel? It will probably take a whole day to charge with a 800mA charger, but will it work?

I also wired up my 50Led light to a fully charged double cell, and am quite happy with the amount of light I'm getting. Next, I'm going to wire it with a protected 2-cell pack & make sure the board does not limit discharge current too much, I want it to be about 1A. If all is working fine, I'll then order the AMC7135 boards, and hold off the Cree project until I sort out other issues - lighting is only one of them, I also need good sound for my videos. I also like the fact that a 50Led light is not too bright for people to look at.

Is there a single inexpensive charger that could deliver, say, 2.5A to a 6-cell pack?

Again, thanks for your help! I've been glued to this forum ever since I found it last week, and I still have so much to learn!