How to run two strips in parallel

[venicenerd]

Hi guys,

I am completely new to programmable RGBW strips and need your help in making sure that my first project will be a success.

I am installing two runs of this RGBW strip in recessed channels along my opposing sites of my ceiling. The run, however, won't be continuous. Each side has an interruption that I will need to bridged with a data cable. Have a look at my drawing:



I am planning to use this power supply.

I would like to run these two strips in parallel. So the left and right strip should always mirror each other. Like twins.  

I have a couple of questions:

1) What is the best way to connect the two data cable runs to the Arduino? Option 1 (each run connects separately to the controller) or option 2 (the two runs are connected as one run)? I really haven't understood this part at all and would love your advise.

2) Will my power connection work? I read in the RGBW strip description that I shouldn't go further than 16' feet without supplying power again. So the way I have it set up is that the first part of 13'2 and the send part of 7'3 (for both sides) will each be connected directly to the power supply.

3) What kind of cable to I need to bridge the data connection between the two parts?

4) Since I need to cut the strip to length for each part of my run I won't be able to connect via the supplied GIFT data connectors. Do I just solder these cables directly onto the strip? Do I buy more GIFT data connectors? How is this done?

Right now I'm just trying to figure out as quickly as possible how to connect these strips to power and data since my drywall will go up next week and I need to get all the cables in place. Once that is done I can figure out the next part on actually building an Arduino and figuring out the software side. I just need to get all the cables in place before the drywall goes up.

I would really appreciate your help!

[Grumpy_Mike]

Send the power to both ends of the strip.
Just wire the data line to both strips to a single wire on the Arduino. Use a separate resistor for each strip and a separate capacitor on each strip.

Have a look at my drawing:

https://imgur.com/EYQ2HAY

No that site wants to infect my computer with all sorts of tracking software so we like you to post images like you have direct to the site.

For a wiring guide see https://learn.adafruit.com/adafruit-neopixel-uberguide/basic-connections

As to power supply current capacity allow 60 mA per LED.

3) What kind of cable to I need to bridge the data connection between the two parts?

Use flat ribbon cable, avoid twisted pair wires.

Do I just solder these cables directly onto the strip?

It is up to you but I would.

[venicenerd]

Thank you! Quick follow up:

"Send the power to both ends of the strip.
Just wire the data line to both strips to a single wire on the Arduino. Use a separate resistor for each strip and a separate capacitor on each strip."

Can I do that as I have shown in my drawing (where I basically supply power at the start of each of the two parts) or do I need to supply power at the beginning of part 1 and then end of part 2? Or does it not matter?

[Grumpy_Mike]

It is better if you supply power to both ends of the strip rather than thinking that power applied to the start of the second strip after the gap is the same as power applied to the end of the strip before the gap. It would also be good to fit a capacitor before the second strip as well.

The idea is to reduce the resistance inherent in the PCB's Power track of the strip.

[Paul__B]

No that site wants to infect my computer with all sorts of tracking software so we like you to post images like you have direct to the site.

No there is no need to upload the picture to the Arduino site itself.  What we want is just the link to the image itself.  Let's stop mucking about and see it properly:

Now, these strips are 60 LEDs per metre.  That is 3.6 Amps per metre.  I figure you need to provide power in parallel every two metres at least so that no part is more than 3.6 Amps away from the power feed at full intensity,  Actually, it is RGBW - unless I have missed something that amounts to 4.8 Amps per metre at full intensity.  So yes, feed the power in parallel every two metres, including both ends.

Are you going to power the Arduino from the same power supply?  Might as well if it is regulated 5 V since that is the right voltage for the Arduino - presumably a Nano.

Well, everywhere you run data, it must be data and ground  Waste of time deploying lots of connectors because they only introduce potential points of failure.  Solder the connection to the strips - the power from the power feeder cables taps into the strip without cutting as it has to feed into both directions.

All wiring, power or data, must be in pairs or as a triple where the data is included.  Since you are powering the Arduino from the system - there is no reason to do otherwise - you bring the power back from the start of the two strips (Option 1) with the data cable, not separately.  Remember - every cable for data includes at least the ground wire.  And keep the power feeders along the strip as far as possible; avoid making open loops.

As Mike points out, where there is any significant length of data cable between to separate sections, you want a 470 Ohm resistor in series with the data line at the input to the next strip, and preferably a 100µF capacitor across the power.

[venicenerd]

Thanks for all the feedback, guys! I have read the tutorials you sent my way and revised my drawing accordingly:



Does that look about right now? I have included the transistors and capacitors in there as well. Do you think it is okay to just run one 10Gauge power cable alongside my strip and the just splice in as shown? Otherwise I'm going to have to run a ton of cable if I always need to go directly back to the Power Source.

Thanks!

[Grumpy_Mike]

Does that look about right now?

Looks fine to me.

I have included the transistors resistors and capacitors in there as well.

Not sure how thick 10 gage is, is that AWG or SWG?

[venicenerd]

Not sure how thick 10 gage is, is that AWG or SWG?

I have ordered this cable for the power:
https://www.amazon.com/gp/product/B074S12G91/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

I would like to run just one power cable parallel to each strip so that I can tap in here and there for more power. Do you think this is good? Or can I get away with a thinner cable? The total power run is about 25' for each strip.

[Grumpy_Mike]

I would like to run just one power cable parallel to each strip so that I can tap in here and there for more power. Do you think this is good?

Yes. This is enormous compared to the strip's PCB track.

Or can I get away with a thinner cable?

I am sure you can. I would say you could get away with 14 AWG.

[Paul__B]

That cable certainly looks adequate for the job; I cannot really get a sense for it just from the picture.  But for that length of cable at 5 V, you certainly need it to be substantial since you do not really want even half a Volt of drop.

And yes, it should be run as far as possible together with the LED strip, not separate branches.  And it should tap in halfway along the longer section of LEDs as well.

Your diagram is almost correct.  It does not emphasise however that the data line is always paired with the ground.  So the power run - 5 V and ground - to the Arduino should not be a separate run; it should run from the start of the LED strip back to the Arduino as one bundle with the data line.  This 5 V line is not carrying any substantial current so it does not need to be such heavy cable however if you run it back from only one LED strip (as you only need it from one) then the ground travelling with the data from the Arduino to both LED strips should be reasonably heavy as you do not want voltage drops due to the current drawn by the LED strips.

Also note - the capacitors need to be at the LED strips as that is where they are needed, not at the power supply which already has an output capacitor.

[venicenerd]

I am sure you can. I would say you could get away with 14 AWG.

I found this Volatage drop calculator. Not sure, though, what I should enter for load current...

Your diagram is almost correct.  It does not emphasise however that the data line is always paired with the ground.  So the power run - 5 V and ground - to the Arduino should not be a separate run; it should run from the start of the LED strip back to the Arduino as one bundle with the data line.  This 5 V line is not carrying any substantial current so it does not need to be such heavy cable however if you run it back from only one LED strip (as you only need it from one) then the ground travelling with the data from the Arduino to both LED strips should be reasonably heavy as you do not want voltage drops due to the current drawn by the LED strips.

There's a lot to process in that paragraph. Do you mean something like this?



Or did I misunderstand?

Also, I read in a couple of tutorials that you should supply power every 6.5' - 9.8'. So I should be pretty solid with supplying power at the beginning and end of my 13'2 run as well as the beginning of my 7'3 run, correct? It will be challenging to make multiple connections since all of this will happen in a very tight, recessed, channel. So unless I absolutely MUST make more power drops I would like to avoid it.

[Grumpy_Mike]

Not sure, though, what I should enter for load current.

Allow 60mA per LED.

[Paul__B]

There's a lot to process in that paragraph. Do you mean something like this?

Well, not quite.

You show separate wires connecting the ground of the power supply to the Arduino and the data to the strips.  You need to  always run the data and ground wire together.  Since the data wire goes from the Arduino to the strip, the ground must go with it as a pair from the Arduino to the strip.  Since you have a data wire to each of two strips, then a ground must go with each data wire as a pair from the Arduino to each strip.

Now you want 5 V power for the Arduino.  This means that you need to run the 5 V line as a triplet from the start of  one strip back to the Arduino along with the ground - and necessarily, the data wire also.  Ground and data always travel together, and Ground and 5 V always travel together.  Three is not a crowd.  

Also, I read in a couple of tutorials that you should supply power every 6.5' - 9.8'. So I should be pretty solid with supplying power at the beginning and end of my 13'2 run as well as the beginning of my 7'3 run, correct?

No.  If you read in tutorials that you should supply power every 6.5' - 9.8, then 7'3 is in that specified range and so "every" 6.5' - 9'8 means at two points 7'3 apart, which means the beginning and end of that strip.

And since 13'2 is twice that length, then "every" 6.5' - 9'8 clearly means the first end, 7'3 into that strip and the other end.

It will be challenging to make multiple connections since all of this will happen in a very tight, recessed, channel. So unless I absolutely MUST make more power drops I would like to avoid it.

It should not be difficult.  It means baring the 5 V and ground at that point for a few mm, soldering a jumper the few mm to each of the two pads on the adjacent strip, and ensuring there is insulation between the two wires.  A wedge of plastic or PCB substrate material, and covered in epoxy.


Why all this talk about keeping the wires together?  It's called a transmission line.  We are talking about radio frequencies here, similar to those used on your AM radio.  Wires that are not kept together are called antennae, used to transmit and receive - in this case, RF interference and impulse surges.

[PaulRB]

I read in a couple of tutorials that you should supply power every 6.5' - 9.8'.

Yes, but how many LEDs per metre on the strips in those tutorials? 30 LEDs per metre is the most common, but you are using 60 leds per metre strips, so twice the current for a given length.

I also noticed on your later diagrams that you are using the same Arduino pin for both strips. You also said that you only wanted simple colour changes and fixed colours. If that's always going to be true, then ok. The two sides will always show identical colours/patterns, and your Arduino sketch will be set up with half the actual number of LEDs than there really are. But in case you later change your mind and want to have full control over all LEDs in the two strips, then you either need to use two Arduino pins, or chain the second strip to the first like in your original diagrams (with another 470R resistor).

[venicenerd]

Well, not quite.

You show separate wires connecting the ground of the power supply to the Arduino and the data to the strips.  You need to  always run the data and ground wire together.  Since the data wire goes from the Arduino to the strip, the ground must go with it as a pair from the Arduino to the strip.  Since you have a data wire to each of two strips, then a ground must go with each data wire as a pair from the Arduino to each strip.

Now you want 5 V power for the Arduino.  This means that you need to run the 5 V line as a triplet from the start of  one strip back to the Arduino along with the ground - and necessarily, the data wire also.  Ground and data always travel together, and Ground and 5 V always travel together.  Three is not a crowd.  

I think my head is about to explode. I really don't know why I cannot understand this. I'm sure it's not that complicated but my head can not wrap itself around whatever you are saying. Do you happen to have Adobe Illustrator installed on your computer? Maybe you have a moment to "correct" my drawing?

I was looking at this image while creating my illustration:


I thought I had done the same?