# Drive a SMD 505012v led strip with a Li-on Battery



## fortunados (Mar 4, 2013)

Hello All
As the title says. I am planning to drive two pieces of a led strip SMD5050 12v with a single li-ion battery a 18650 2200 mAh battery, or maybe two. Echa strip 3 leds only, I think is the minimum you can cut out the strip.

.I have thought a lot and I have to options, 

1.- remove the resistors from the strips and change them for a smaller ones line 10 Ohms in order to get light out of 4v the is the normal voltage of the li-ion battery.

2.- Use a step up voltage converter from 4v to 12, something like This.

I have also a space problem because I am planning to put all the system inside a 2,2 cm diameter tube. That would be 0.87 inches diameter tube I believe.

I wonder which would be the most energy efficient option in order to get the maximum from the battery.

I have looked around a lot but it seems the not many people has changed the resistors from the stripes. I guess It should not be difficult although there are smd resistors.

Any help or suggestions would be very apprecciated.

Thanks a lot.


----------



## Optical Inferno (Mar 4, 2013)

What is your application? If you would explain a little more, others may be able to offer their opinion. I wouldn't remove the resistors as they are related not to just the current through the system, but also the parallel/series layout of the LEDs.


----------



## fortunados (Mar 4, 2013)

I am planning to use it as lights in a handlebar for a bike

2 short strips SMD 5050 of 3 leds each one, both of them feeded by one 18650 battery, all inside the handlebar with a switch.

The problem is that those strips have to be feeded by 12V adn the battery voltage is from 4,1 to 3,7 volts, so I have the two options, change the resistors in the strip or use the booster dc dc step up convertor.

I wonder wich option is the most effective for the battery lasting, I mean which option will get me more time from the battery.

thanks a lot


----------



## Ken_McE (Mar 4, 2013)

As a practical matter, I believe it would be pure hell to try and cut the leads to those resistors and then create new leads to go around them. :sick2: 

Any chance you could get three of those 4 volt batteries, hook them up in series?


----------



## fortunados (Mar 5, 2013)

Well, I believe that there wouldn't be physical space to put them, I think that the maximum that I could acommodate would be two batteries, but this would be plan b.

The mayor difficult would be to integrate the leds in the handlebar to make it nice and neat, Its rather difficult to put the leds in a so tight tube, you can work on from outside only, but thats a physical problem. 

This is the idea but with smd5050 and 18650 battery, all inside.






I think that I saw one of those strips for sell withouth components ( leds and resistors ) to solder them. Another approach could be buy one of those, solder the leds and the appropiate resistors.

Maybe I could use one of those flashlight drivers to drive the current to the strip

¿What do you think?

Thanks a lot


----------



## Optical Inferno (Mar 5, 2013)

Is there a reason why you want to use an off the shelf strip instead of your own design. If you were to re-design something yourself, you could hook all the LEDs in parallel thus maintaining a forward voltage ~3.0-3.2V and use one battery with a current limiting setup.

Interesting design, but I question the amount of useful light that would be available as SMD5050 LEDs usually put out about 90-100lms with fairly low efficacy. Also, how are you going to cool them? They won't last very long on their own.


----------



## Ken_McE (Mar 5, 2013)

Optical Inferno said:


> I question the amount of useful light that would be available as SMD5050 LEDs usually put out about 90-100lms with fairly low efficacy.



I assumed that they were to let other people see him coming, not to light anything up.



> Also, how are you going to cool them? They won't last very long on their own.



I thought the handlebar tube would suffice. 5050s don't make that much heat, and it is naturally diffused.


----------



## Ken_McE (Mar 5, 2013)

fortunados said:


> Well, I believe that there wouldn't be physical space to put them, I think that the maximum that I could acommodate would be two batteries



What if you put one inside the left end of the handlebars, two inside the right, ran a wire to connect them? That wire would also be the on/off switch.



> This is the idea but with smd5050 and 18650 battery, all inside.



You are setting an impressively high standard. If you can do this, it will be very elegant.



> Thanks a lot



De nada.


----------



## fortunados (Mar 6, 2013)

You are right, It's more to be seen that to see.

I also thought about that the wind speed and the handlebar should be more than enought to cool them. I thouth that they cannot generate too much heat if they come in a strip.

I am thinking as per your suggestions that maybe would be better and approach from the side of stand alone leds hooked in parallel with a resistor around 8-10 Ohms each.

That would be much more neat, I don't think that shoule be much difficult to solder, It could be used with one or two batteries only ( I thinks that it's more than enough and I try to avoid innecesary weight with more batteries) with a switcher in the bar end plug could be nice.

Thanks for all the ideas and help.

The major difficul would be to comple a maximum integration of the leds in the handlebar, and this is one of those things that you are taking with you to bed everyday until any good idea appears.

Right now my best choice is to look for any through-hole nice bezel or plastic diffuser or something like that that in the other side would help to concentrate the ligth a little bit and would protect them a little bit.

Thanks again.


----------



## WeLight (Mar 8, 2013)

You can purchase 3volt ribbon if your looking for a low voltage based solution


----------



## fortunados (Mar 10, 2013)

Do you mean 3v led strip ?

Actually my last approach is that I am using 6 white 5mm in paralel with a resistor each.

I have tested them with a 47 ohm resistor each and I got 17 ours out of single 1860 battery and stopped the test with a voltage of 2,9 v remaining.

I am looking for a constant current 120ma driver for this and remove the resistors in order to maximize the battery performance and to get a constant not dimming lighting depending of the voltage.

I was surfing the web for 2-3 days and there are not many options, just one or two things like this circuit that looks like a configurable costant current low power driver.

I really would like to have one of these small smallflashlight drives that allow two modes or more. There are thousans but the problem is that the minimum current is 350mA that it's the 7135 allows, Ilooks like is not possible to reduce the current changing the resistors.

I have seen some back-boost circuits like this one BUT it looks like it is not limiting the current, just the voltage and the current in the specs it's maximum allowed so it looks like this would not perform the task, am I right?

To sum up i need a constant current 120mA to drive 6 paraled leds which can work out of a single liion 18650 battery and doesn't seems to be many out there.

Once again thanks for your time.


----------



## WeLight (Mar 10, 2013)

Yes 5m rolls that operate at 3VDC


----------



## CuriousOne (Mar 15, 2013)

If you can do soldering, you can assemble a special driver, using an IC, which is dedicated for backlight led driving in portable applications. For example ON Semiconductors CAT4240. I have tested this driver with single cell Li-ion battery, and it will light up up to 3 strings of 3 leds in your config.


----------



## fortunados (Mar 16, 2013)

CuriousOne said:


> If you can do soldering, you can assemble a special driver, using an IC, which is dedicated for backlight led driving in portable applications. For example ON Semiconductors CAT4240. I have tested this driver with single cell Li-ion battery, and it will light up up to 3 strings of 3 leds in your config.



This is what I was looking for, something like a flashlight driver to avoid all the trouble that could be easy modify by changing the resistors to provide my 120mA current but there is no luck or they are outrageous expensive.

I was looking as well for IC to drive the leds as you said, I can solder, but the point is that It's quite difficult to put all this stuff inside a 18mm tube so I was looking for as less attached components IC as possible, more than 3 or 4 I think that would be difficult. 

I found LT3090, LT3491, LT3465, MP3302 and LM3914.

I am going to have a look at that CAT4240, It looks like it needs 5 or 6 anex components.

Thanks a lot.


----------



## Julian Holtz (Mar 25, 2013)

The best solution would indeed be a switching regulator which boosts the voltage to 12V, as mentioned in your first posting. It would also conveniently fit in your tube.

Even this one would fit, if you remove some of the components on the trimmer side, carefully trace the traces and solder them elswhere, perhaps connected with wires.


http://www.ebay.de/itm/Hotsell-LM25...970?pt=LH_DefaultDomain_0&hash=item1c2fea5a42


----------

