RBG "dumb" strips - how many can be connected together

[mattpatt]

I'm putting dumb strips on my house and just received them from China. Curious what the general consensus is on connecting dumb strips together. I was hoping to run two strips per RGB channel on my LOR DC controller. Is that possible? I noticed on the package that is says that it must not exceed 5 meters when used in a DC circuit.

Thanks,

Matt

Edited August 31, 2012 by mattpatt

[CLD Kevin]

I'm personally used (2) 5m strips per RGB channel (3). Now if you going to run them in series I heard different stories. Some can and others see the 2nd strip dimmer. I guess it all depends on the power source, cable size, distance, ect. All these things plays a role. I have run (2) 5m strips in series and didn't have any problems. But again, I had a strong power source, good size cable and short distance.

May be best to split the power/signal between the 2 strips than run in series. This would be your best option to make sure there is no problems.

Edited August 31, 2012 by CLD Kevin

[Shubb]

Instead of running the 2 ribbons in series, can you connect them in the middle?

That way each ribbon see's full incoming 12v.

[TJ Hvasta]

Thats what I'm planning too, dont feed it at the end, in series, feed it in the middle of the two strips.. the strips I got say 1.2A @ 12, I'm thinking that RGB, (all three lit), so abt .4a-ish per color (as a guide) for load planning. two strips/channel, all on, is abt 2.5a. Just plan accordingly with/for your power supply.

[MtDew4me]

Perhaps I am confused about something.....

I have 5m 12v strips with 30 RGB 5050 LEDs per meter. The specs from Ray Wu show 7.2W per meter. Therefore 7.2W/12V=0.6A/m or 0.6*5=3A for the strip. I assume that's at white (ie: all colors on at 100%). Therefore, that's approximately 1A, plus or minus depending on the color, per color/channle per strip. If you power 2 strips, you'd need 2A per channel which I thought would push the LOR DC controller to it's 2A per channel limit.

link to my strips: http://www.aliexpress.com/product-fm/329544925-5m-one-roll-5050-SMD-30LEDs-m-led-strip-waterproof-by-silicon-tubing-and-coating-RGB-wholesalers.html

Where am I going wrong in my understanding?

Edited August 31, 2012 by MtDew4me

[TJ Hvasta]

hmm, you didn't mention you had Ray's strips, just ones from China which are "generally" 1-2a/strip.. the ones I have are 1.2a per strip.. or .4a/color.. your mileage may vary.. I think I remember 2amp/channel without heatsinks. And these being hot tabs, you would need isolating kits to bolt on sinks. I dont recall what the limit was per "sink'ed" channel tho.. would have to read the manual.

[mattpatt]

Thanks everyone. Feeding the two strips in the middle sounds like a plan. The way my house is setup. I have 3 channels setup for the roof line with two strips each then a 1 channel front window with 1.5 strips and a 1 channel outline of the garage with two strips. That will max out my LOR DC controller. I was worried that I might have to buy another controller, power supply, enclosure, etc. All my strips came in yesterday. Need to building the controller so I can start playing.

Matt

[Santas Helper]

hmm, you didn't mention you had Ray's strips, just ones from China which are "generally" 1-2a/strip.. the ones I have are 1.2a per strip.. or .4a/color.. your mileage may vary.. I think I remember 2amp/channel without heatsinks. And these being hot tabs, you would need isolating kits to bolt on sinks. I dont recall what the limit was per "sink'ed" channel tho.. would have to read the manual.

Here is from the manual for the LOR DC controller. As long as you don't go over channel capacity, bank capacity or board capacity you should be fine.

CMB16D-QC

Specifications

Individual Channel Capacity

4 amps – No Heat Sinks

8 amps – Regular Heat Sinks

Individual Bank Capacity 20 amps

Board Capacity 40 amps

Edited August 31, 2012 by Santas Helper

[TJ Hvasta]

Thanks Tom, the current numbers were escaping my memory, but the limits are good as I'll have two boards to split 160' of strips across..

[Santas Helper]

Thanks Tom, the current numbers were escaping my memory, but the limits are good as I'll have two boards to split 160' of strips across..

TJ, will the 160' of strips be on the same channel on your sequence editor doing the same thing? If so, I'll have a similar scenerio as I boarder my house roof line with these and was curious how yours would be connected up power wise to the controllers.

[Max-Paul]

Hi Guys,

Not doing RGB strips yet, but interested and read what ya'll are doing. Two threads lately have me confussed. First we have this one here where you all are saying that the ray wu strips draw 1.2 amps with all LEDs lit. And by strips I presume you are talking the whole 5 meters? Yet in the other thread TJ offers up a link to the strips and I have here a quote that says it is 1.2 amps per meter or 6 amps for the whole strip.

"Working Current/meter: 1.2A

Output power: 36W /5 Meter"

So is this a typo from the ebay listing? Or is it .4 amps X 5 = 2 amps per color for each strip? So putting two strips in series (actually parallel electrically) will raise the current draw on each channel to the max of 4 amps. I do not know how much underrating LOR did on those specs that Tom posted. Would consider taking the extra steps and install the heat sink?

[CLD Kevin]

Brandon....and this applies to all. Dont pay attention to what the package states. We would all like to believe it to be true and accurate, but unfortunately they are not. It would be best to take your own reading via multimeter. My strips are 1.75A all on even the package stated it was something like 3A.

Powering from the middle or between is the best way to get the max length per channel. Since there is no perfect answer for every setup, best to test yourself.

[Max-Paul]

Who's Brandon? Kevin.

[Santas Helper]

Who's Brandon? Kevin.

I believe it's Matt's secret middle name.

It's actually MtDew's name.

Edited September 1, 2012 by Santas Helper

[TJ Hvasta]

Thanks Kevin, always good to get the true info from the guy who knows!!

MP, yes, I did misread it too after I posted, 1.2A/m, and I have 5 sections of roof to do, and 3 sections of vertical house lines, so 8 total, across two (if I get the one that got fried by the AC controller fixed) DC controllers, so I'm thinking I'll be ok on the current requirements ladder.. 50m x 1.2-ish divided by two boards.. I think about 16-ish amps per bank.. And thats if they're all on, which I'm not planning on white (rgb on) being one of my color choices..

Tom, with the two boards, each eave(rafter) will either have two strips(6channels) or two strips per channel, havent decided yet. 10 strips (7 eave sections & 3 vertical runs) / 32channels.. or 4 eaves & 3 vertical sections / 32channels.. I still have to "wire it up" in the visualizer and see which looks better.. running 7 seperate segments allows a "bit" of a chase, sort of.. but this is the forst year, so I'm flexible.

Edited September 1, 2012 by TJ Hvasta

[Ken Benedict]

Keep in mind that there are two basic kinds of "dumb" strips; 30 LEDs per meter and 60 LEDs per meter and the current draw is different.

Sometimes they are rated at 150 LEDs per strip or 300 LEDs per strip. Assuming 5 meter strips;

The 150 LED versions draw 1.75-2.00 amps total with all LEDs on.

The 300 LED versions draw 2.8-3.2 amps total with all LEDs on.

There is some variance between strips.

Calculate your load accordingly and go a little over on the power supply rating, for insurance.

It does not matter if the strips are RGB or single color; current draw is pretty much the same.

PS: There is a hard to find strip rated at 144 LEDs per meter, but they don't seem to be as popular or accessible as the others.

Edited September 4, 2012 by Ken Benedict

[edvas69]

The reason why the calculated current drawn and the measured current drawn differ is mainly due to voltage drop.

The 5050 LEDs used in strip are 60mA each total, that means they are 20mA per colour, now that is the designed specification of the 5050 LEDs

So when we calculate that over 1 meter for the common 30 LED/Metre strip at 12vdc with 3 LEDs in series per section we end up with 0.2 amp per metre per colour

So 10 sections per metre x 0.02amps = 0.2 amps

0.2 amps per metre x 5 metres = 1 amp per colour

So the common return should see 3 amps when all LEDs are 100%

So why is the measured reading different. There are a few reasons for this and its to do with the relationship of voltage, resistance and current (Ohms Law)

The resistor value used can reduce the current used by the LEDs, some vendors will use this method due to using lower quality LEDs, so they under drive them to extend their life.

and

With voltage drop you will see current draw drop as well. The voltage drop will be seen within the strip itself and also with the cable supplying the strip

So if we had a strip where the first section was seeing 12vdc and the current limiting resistor was 600 ohms then we will see:

Volts x Resistance = current

12v x 600ohms = 0.02 amps (20mA)

so as you see a 600ohm resistor should be a close fit for running at 12vdc for the 5050 LEDs to be driven at 20mA

Now if the end of the strip is seeing 10 volts then the current drawn will be less

10v x 600ohms = 0.01667 amps (16.7mA)

So this will explain why we see different results to what is calculated. I always design my system for the calculated load and not the measured load as this is the safest way that gives you some head room.

Edited September 4, 2012 by edvas69

[edvas69]

Please note for some reason i have written the actual calculation of Ohms law incorrect but i calculated the correct result, DOH!

but i cant edit the the post so ill put the correct calculation here

12v/600ohms = 20mA

and

10v/600Ohms = 16.7mA

so in summary Ohms law is

Voltage = current x resistance

Current = voltage / resistance

Resistance = voltage / current

and a couple of commonly used extras

Power (watts) = Volts x current

Voltage = power / current

Current = power / volts

Edited September 4, 2012 by edvas69

[Ken Benedict]

For those people running multiple RGB strips end-to-end, you should use an RGB Amplifier, to boost the signal and inject more power to avoid a power loss at the end of the strip.

Sample: http://www.ebay.com/itm/Mini-Red-12V-12A-Signal-Amplifier-RGB-5050-3528-SMD-LED-Strips-Lights-/160812487229?pt=LH_DefaultDomain_0&hash=item25712bd23d

This is assuming that all the strips will be the same color at the same time.

For individual strip control, run an RGB line back to the DC controller of your choice.

For individual pixel control, like a 6803 (CCR) or 2811 or whatever type you use, you would need a pixel controller at the start of the string.

The LOR CCR/CCP/CCF products already have amazing controllers that come with the strips.

Keep in mind that even with pixel control, the math is the same for current loads for your strips.

Most strips are 12 volts, but there are 5 volt versions and 24 volt versions out there also.

Keep this in mind when connecting to your power supply, or you will let the Secret Smoke out of your precious lighting strips; hard to put back in.

[edvas69]

Now with the above calculation showing how voltage affects the current drawn we can now also explain why constant current control is better for LEDs (especially high power LEDs) than voltage control.

The LEDs in a dumb strip are controlled by voltage, so what happens is the voltage plays an important part here when it comes to the current drawn by the LED. The LED circuit current limiting resistor is set so this value doesnt change. So with voltage control, any fluctuations in voltage (voltage drop) effect the current put through the LED and thus effect the light output. Nearly all our dumb strip used in the hobby is controlled in this manner.

But due to the fact that the human eye does not see linear and the light output from an LED is linear by nature, then we do not see these light output differences very easily between an under driven and a over driven LED especially with anything that is drawing above 15mA

Now with intelligent strip each LED circuit/section now has its own LED driver, The LED driver controls current instead of voltage. the same current will be maintained as long as the voltage supplied does not go below that of the LED circuit voltage, so for an LED that is rated at 3.1 volts with 3 LEDs in series, then the voltage must go below 9.3 volts before the supplied current to the LED circuit starts to lower. This is why constant current is the prefered choice when it comes to driving LEDs as it is much more stable and will not overdrive the LEDs if the voltage is slightly higher or will not under drive them if the voltage is a bit lower. There are some intelligent strip and strings that use constant voltage as the driver for the LEDs like the 180x series used in the 12vdc pixel string but thats a different subject as to why.

Edited September 4, 2012 by edvas69