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Topic: Powering Portable Led Strips (Read 2119 times) previous topic - next topic

snoche

Hi guys,

I am new to this world of arduino and this is my first post, I finally realized I need professional advices hehe, sorry if I say something stupid, still learning.

I am making a cylindrical car and I have attached 180 leds WS212B.
The leds alone uses 50W (10.8A) and I will need 4 motors too and some sensor too.

I have been looking a lot about powering this but I am still very confused.  :smiley-confuse:

Which of this makes more sense for you to use as a power supply?

- A Lipoly 3.7 battery with a step up module to 5v,
- 4 battery NiMh (4,8v). This will give me enought current for the leds?
- 2 LiFePO A123 batteries (6.6v) and use them to power Arduino directly and a step down or a diode to power the leds.

Do you think I should have different power supply for arduino and the leds?
What is better to use a step up module or step down? or I should avoid them at all?

Could you guys recommend me too a good charger for Lipo, LiFePO?



Thank you very much,
David







INTP

Check your math or check your plans. No way should you even be thinking about a 3.7V lipo giving you 10+Amps.

Grumpy_Mike

You can't get a step up regulator to give you 10A, well not one you could afford. It also means you are drawing over 10A on the input from your battery. The whole project sounds unrealistic.

PaulRB

#3
Sep 25, 2016, 10:19 am Last Edit: Sep 25, 2016, 10:38 am by PaulRB
That 10.8A is the maximum when all leds in the strip are at full brightness white. But, for example, if only one led in three is on at any instant, showing red, green or blue at 33% brightness, the total current will be 10.8 x 1/3 x 1/3 x 1/3 = 0.4A. So by using flashing patterns, using reduced brightness etc. you can greatly reduce the demand on your batteries.

There is a potential problem with this idea. What happens when your strip is first powered up? My strips default to all off. But I hear that some strips do not, and might use a significant current when powered up, until your sketch takes control. There is also the danger that an error in your sketch could lead to the strip drawing too much current and damaging some of your components. If you use the FastLED library, you can set an overall brightness level of, say, 10% for testing. When you know your code is producing the correct flashing patters & colours, then you can turn up the brightness.

snoche

I should mention I have 4 strips of 45 leds each, and I have tested with a power supply at 5v, it drains about 1.5A, I am not sure why I kind drain more Amperes at 5V, probably is a limitation of my cheap power supply (60v-5A).

If I put all the leds on with high brightness and all white I can see the dimmer going to yellowish at the last leds.

My connection is in progressive and I only power the first row, probably I should power the 4 strips in parallel?

Paul, this is absolutely a good idea, yes I am using FastLed and I was thinking to lower the brightness and probably my best bet will be to only have some leds on in a normal state, like some rotating Leds or something, I don't need to have all them lite at once and I don't need them to be very bright as is only for indication, I may lite them all when is detecting collisions or something but could be a couple of seconds and flashing, I think I will not use more than 2-3 amperes realistically, but I was calculating the maximums, some dimmer for me is acceptable too.

I have also tested powering them with 3 AAA batteries, and they work with some dimmer, so I don't think is such an unrealistic project if I found a good way to power the strips.

What I am looking for is the best way to power it, maybe 2 Lipo batteries? space and weight is not a problem for this project.


"You can't get a step up regulator to give you 10A, "
I could not drain 10A from Lipo batteries?

how about If I use 2 or 3 LiFePO batteries and step down? this will be better and safer? I have read you can get lot of Amperes from them.

Or will be even better a 12v battery and a step down?














Grumpy_Mike

Quote
I should mention I have 4 strips of 45 leds each, and I have tested with a power supply at 5v, it drains about 1.5A,
That is just 8.3mA per LED. How did you test this? Most multimeters can not measure pulsing current very accurately.

Quote
I have also tested powering them with 3 AAA batteries, and they work with some dimmer,
What voltage were you getting out of your battery both under load and free of load.

A buck converter is normally more efficient than a step up.

I see you are backing off from your original specification, the more you do the more realistic is your project.

snoche

Hi, I have tested it with a power supply and with 3 AAA batteries.

When I use the power supply, it drains 1 - 1.5 Amperes, I am not sure why it doesn't drain more for the power supply. Is what it says on the led display, I have also tested with a multimeter Unit-T UT61E.

With all lights full brighness is about 2.5v in the first led and 2.3v in the last led. With the FastLed demoscene about 2.4v to 2.3v.

Some measurements whit a power supply at 5.0v
Full red brighness
First Led > 2.953v
Last Led > 2.528v

Full Wite brighness
First Led > 2.734v    1.1A
Last Led > 2.317v    0.003A

I have connected the 4 rows to the 5v and ground in parallel and it works better now, at least I got less dimmer in the lights.


Why I can not drain more Amperes from my power supply (60v,5A)?, is it because this power supply could be limited for the 5A with higher Voltage?

Does anyone has a recommendation of a power supply (portable) I should buy for 5v and high Appears?






Grumpy_Mike

What size is your bulk smoothing capacitor across the supply, in fact do you have one? That might explain why the power supply is giving up because the current is being chopped and the bulk capacitors inside the power supply are not going to be able to cope with this by themselves. I also assume you have a resistor in the data line out to the first LED.

snoche

Sorry for the delay, for some reason the emails from the forum went to the spam folder.

I am not sure about the smoothing capacitor, I connect the output from the power supply directly to the inputs of the led strip without any resistor or capacitor, and the data line out directly to the Arduino.


Grumpy_Mike

That might explain why you are having problems then.

snoche

Should I add a capacitor between the power supply and the led strip? if yes, which size you recommend me?

And a resistor to the data in? which size?

Should I connect the end of the strip to the ground and voltage too? or it doesn't matter.

I also have now 2 battery samsung 18650 30Q, which should allow me to drain 15A a step down regulator for my test. I hope it works.

Thank you.

Grumpy_Mike

Quote
Should I add a capacitor between the power supply and the led strip?
No.
You should add the capacitor between the + and the - of the strip.
Quote
which size you recommend me?
At least 1000 uF

Quote
And a resistor to the data in? which size?
About 470R but not too critical around that value.

Quote
Should I connect the end of the strip to the ground and voltage too? or it doesn't matter.
I would connect the power connectors at the end of the strip to the power connectors at the start of the strip. That will improve the circuit.

Quote
which should allow me to drain 15A a step down regulator
That is a very big step down regulator.

snoche

Thanks Mike I will try to add those components and check the intensity again.

The step down is not that big, the 2 batteries give me a total of 7.4 v and I have adjusted the output of the step down to 5v, as I understand is not that match heat generated isn´t?

This is the step down I will be using

https://es.aliexpress.com/store/product/Mini360-DC-DC-Buck-Converter-Step-Down-Module-4-75V-23V-to-1V-17V-17x11x3-8mm/1022067_32582982343.html?spm=2114.12010408.1000016.1.1UiITi&isOrigTitle=true


snoche

#13
Oct 28, 2016, 05:39 pm Last Edit: Oct 28, 2016, 05:54 pm by snoche
I made some new test and I added a capacitor of 470uF (is the biggest I have here) and a resistor of 470.

I couldn't see any difference in the numbers adding them, I guess is just for protection.

I also tested the 18650 batteries, they are awesome and I got full white and measured a 6.1 amperes. Some cable melt and I replaced with proper 22 gauge ones.

I test it again with the power supply setting maxim voltage to 5v and to 5amps but I got only 1.2 amperes of draining and yellow lights, I measured the real voltage in the strip and it was only 2.5, If I raise the power supply voltage to about 8-9v (the real one in the multimeter, 3.1v) and I got a the desired white colours, it also increase my amperes.

Raising the power supply to the maximum values it can handle 60V, 5A It only displays 12v in the power supply display and 3.3v real voltage in the strip of the power supply, but the cables become too hot.

I don´t understand why this happen, it doesn't looks very safe too me do have to raise the limit of 5v in the power supply.

Does anyone have an idea why is this happening? is this just a cheap crap power supply?

BTW: this is the power supply I am using.
http://www.satkit.com/b2c/index.php?page=pp_producto.php&md=0&ref=KPS6005DA

INTP

You need to give details of your power supply. Make, model, etc.
Voltage drops under load, that's normal, but dropping that much suggests incorrect wiring or insufficient power supply.


18650 cells will typically have a 2C rating, meaning they can provide an amperage of 2 times the capacity. E.g., a 3400mAh 18650 rated 2C can provide 6.8A max. This is highly dependent on the actual capacity of your 18650, which you cannot trust labels for if you're not using a name brand oem cell.

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