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How to inject power


godman
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I understand from reading all the posts that at times it is necessary to inject power to lights. How does one inject power into pixels that need to have a power injected?

 

I understand the concept of why power would be needed as lights are added i'm just not exactly sure how to inject the power.

 

Thanks!

 

 

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Now just speaking of RGB strips. At each end usually but even so at the front end there will be at least 3 or 4 wires. Two of these wires are the power wires, both + and -. Now part of the reason for the power injection is that the gauge of the wires is to small and thus a high resistance. And with resistance, voltage will drop. So to get around this a heavier set of wires are used to carry the voltage from the power supply, say about 16 gauge. Running these wires parallel to the strips. Then use a knife to trim off some of the jacket from the 16 gauge wire near where the power leads are for the strips. Do this for each strip. I suggest that you pick up from some place like Home Depot what is called liquid electric tape and paint the solder joints

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I just bought some Smart pixels for Ray (below) and I'm wondering how many pixels I can run (roughly) before I needing to inject power? From what I read its about 50 (1 string) So with these pixels I would just run two (2) 16g wires (+-) from the same power supply to and splice it in at a ceratin length?
 
Below is what I purchased:
 
 
http://www.aliexpress.com/store/product/promotion-WS2811-IP68-led-pixel-module-256scale-gray-IP68-3wire-red-blue-black-DC5V-input-50pcs/701799_469177597.html

http://www.aliexpress.com/store/product/150W-Dual-Output-Switching-Power-Supply-88-264VAC-input-5V-150W-output-CE-and-ROHS-approved/701799_289599852.html

 

Comments-Suggestions welcomed.
 

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https://www.dropbox.com/s/lejhomxm2s540m6/Strip%20wiring%20and%20Power%20injection.pdf

 

Here is a quick and dirty representation of how to inject power, (assuming the left side is the first pixel on the strip or string). Strip or string, the procedure is the same. I forgot to put a legend on the drawing, but it's pretty much self explanatory. Red is hot, Blue is ground and green is data. This is the way I power inject and have had zero problems.

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Thanks Ron, very helpful, Just another quick question.

 

I believe each power supply has 3 separate outputs (+ -), so 1 output to controller and then there are 2 available to inject (per diagram). Let's assume I need to inject after each 50 string of nodes I then can have 2 strings on the first power supply, If I need a total of 5 strings connected I would need another power supply to power the other 3 strings right? I'm assuming I would be able to power 3 strings on the second power  supply (and so on) because I wouldn't need to power up the controller that was used on the first supply?

 

Does that make sense?

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http://www.radioshack.com/product/index.jsp?productId=2103986&filterName=Cable+type&filterValue=Terminal+strip

 

Just use one of these on the Power Supply. Use some 14 gauge or 12 gauge wire to create jumpers on one side and bring the power from the PS to one of the jumpered posts. Then it's just a matter of running wire from the terminal strip to your injection points.

 

This is the way I do it. Not necessarily the right way or the best way, just the way I do.

 

Some are using a PS such as a 24 volt and using step down boards to bring the voltage to the 5v or 12v they need. I haven't done any studying on that way to do it, so I can't help you there, but I know it's been done

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From the picture on that link, it looks like two V+ and two Com terminals.  I seriously doubt those terminals are separate outputs, they are just separate terminals.  They are internally tied together in the power supply.  I don't think that is a "dual output" supply.. dual terminals perhaps.

 

So with that said, as long as you don't exceed the overall rating of the power supply with your load, you can feed as many strings or ends of strings as you want.  Those wire plates on the terminals are rated for two wires each. That would mean you could put four outputs without having to branch connect to more wires.    If you are using all 50 in each string when you go to white you will use about 3 amps.    That supply is rated for just over 12 amps.. It won't handle 5 strings.  You will need a second supply.  Since you will need a second supply, you might as well split the strings up and put two on one supply and three on the other..

 

As for injecting power, if the string draws 3 amps, it won't make any difference if you inject at both ends or the middle or even at just one end.. it will still draw 3 amps.... OK. the exception to that is if you only feed one end.. the voltage drop will cause you to actually draw less current and it could cause you color shifting problems... so either inject at both ends or just in the middle... But assume 3 amps per string total regardless.

 

There are tons of posts on this subject already.. many with pictures or diagrams.. snoop around and you will find a ton of info that has already been posted. 

 

Have some fun! 

 

EDIT:  If you are not going to do much white, (RGB all on at once), you may not have to inject power anywhere but at the feeder end.  Experiment.... The wired pixels actually do much better than the strips for voltage drop.  But surely you can't feed thru to the next strings and expect it to maintain integrity for color or perhaps even signal.  Just gotta try it.

Edited by plasmadrive
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Thanks Plasma. That's a much better explanation than mine. Makes better sense.

 

I was kind of hoping you might chime in and explain about the higher voltage PS and the step down. I'm still not quite sure I understand that completely. If yo have a write-up or how-to, that would be fantastic. Not only will it help me, but I'm sure many others.

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Thanks Plasma. That's a much better explanation than mine. Makes better sense.

 

I was kind of hoping you might chime in and explain about the higher voltage PS and the step down. I'm still not quite sure I understand that completely. If yo have a write-up or how-to, that would be fantastic. Not only will it help me, but I'm sure many others.

Hey Ron,

 

The way the higher voltage thing works is like this.  Lets assume your lighting load is 24 watts (just to pick a value).....  at 24v that is 1 amp, at 12v that is 2 amps and at 5v that is 4.8 amps.   The thing that causes the voltage drop is the current draw x resistance (of the wire).  So given the same wire, the voltage drop at 24 volts is 1/2 of what it would be at 12v and so on.  (That is why the power company uses higher voltages for power delivery, less loss in the wire). 

 

Using the Plasma Icicles as an example, I ran a single 24v supply for the main house.  I ran all 5v pixels and used DC-DC converters to feed the center of every pair of 1m pixel strips.  That 2m of pixel strips (1m each side of the feed) draws about 3.3 amps.  At 5v x 3.3 amps that is 16.5 watts.  At 24v that is about 0.68amps. 4.8 times less voltage drop due to wire resistance because the current is 4.8 times less.  (I am not accounting for the minor draw of the converters themselves for this example).  If you assume a wire resistance of .3 ohms for whatever length you use, (an arbitrary value)...... using a 5v supply, you would get a 1v drop across the wire. That is a 20% drop in voltage from supply to load.  However at 24v with that same .3 ohms resistance in the wire, at 0.68 amps you get 0.18v drop.  That is a 0.75% drop in voltage.   Both are delivering about 16.5 watts

 

Since the DC-DC converter is a regulator, it take the 24v and drops it to 5v and regulates it at that 5v level.  It really doesn't matter if it has 24v or 8v, the convertor would still give me 5v out as long as it had enough "head room" to regulate.  That means that the voltage drop across the 24v wire length just doesn't matter to the converter because I sized the wire to allow for no more than a 3% drop, (but it could have been a 50% drop and still worked).

 

The other added benefit was that with a 24v 10amp supply, I was able to use #14 wire for the entire run on the main house.  #14 wire is good for 15amps according to the NEC.  The power supply protected the wire.  The DC-DC converters protected their outputs against a short circuit at every drop point since they current limit out at 5 amps (the ones I used).  My entire string was protected without using any fuses.  I didn't have to up size the wire to accommodate for voltage drop even at 65' since the converters didn't care about that drop.  My pixels were all very white when they were called to be that way.. There was 5v at every pixel strip junction pair all the time. 

 

Sorry for the long explanation but I hope it helped.  Any questions??? please just ask...

Edited by plasmadrive
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Ok. I think I'm getting a better understanding of it all. Since I'm going to use 10 sets of the Plasma Icicles from diyledexpress.com, I just might have to give this a try. Thanks for taking the time to explain it.

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You are welcome.  Hope I didn't complicate more than I needed to..  I don't understand why everyone isn't using DC-DC converters and smaller wire.. would eliminate half the problems some people are having..

Edited by plasmadrive
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@Plasma, are you saying its better to use a 24 volt power supply with a DC-DC converter and then the converter will automatically deliver the correct power across the my 5v pixels?

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@Plasma, are you saying its better to use a 24 volt power supply with a DC-DC converter and then the converter will automatically deliver the correct power across the my 5v pixels?

Every situation is different, but if you have any real distance that you need to run wire from the supply to the pixels, then yes.  The converter will deliver 5v right at it's output,  so you want the converter as close to the pixels as you can practically get it.  The voltage drop across the strings or strips is still there and you should make your system accordingly. 

 

The good part about doing it this way is that you can use a 24v supply with the appropriate available power and run much smaller wire to the converters that what you would have had to do to try and maintain that 5v. Then you just tap off where ever you need the 5v and put a converter.

 

BTW, I sent Ray an email about the power supply ad because the numbers didn't add up right... it said both 12v and 5v.  He has corrected it and it now says 12v @ 150watts.   That is plenty of power for all your pixels if you run converters.

 

In your case you have about 15amps worth of pixels at 5v all on. That is about 75 watts.  I don't know how far you have to run wire, but you could use that 12v supply and 5v some DC-DC converters and you would have no power issues.  Use the right size wire for the feeder from the supply and you will be happy with the results. 

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I do have one more question. Do you have a link or a recommendation for the DC-DC converters? 

I have resolved my issues with the company that made the ones I use so I would recommend them now.  ProDCtoDC.com  I use the potted ones since they are waterproof. 

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@ Plasma, I'm a little confused about my power supplies (link above), according to your email to ray you pointed out that they are 12v 150W and not 5V 150 watt? Is there a way of looking at the power supply to tell? The only sticker I see on the supply says:
 
S-150-5
Input 100-120VAC  3.2A
         200-240VAC 1.6A
                           50/60 Hz
Output +5V-------30A
 
I just want to make sure I know what they are. Also on the site ProDCtoDC.com, can you supply a part number or URL so I can make sure I am looking at the right converter?

 

Thanks!

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Ron, your such an artsy fartsy fellow. :P:D great art work to explain.

 

Plasma, I was just about to question your support for the DC to DC converters. But I see that you and the company worked together to improve their product.

 

As for me, I like to keep things simple (KISS). But if I ever do get into a project like yours. I might find myself having to go that way with the DC to DC. Glad to hear your endorsement of their revised product.

Edited by Max-Paul
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@ Plasma, I'm a little confused about my power supplies (link above), according to your email to ray you pointed out that they are 12v 150W and not 5V 150 watt? Is there a way of looking at the power supply to tell? The only sticker I see on the supply says:

 

S-150-5

Input 100-120VAC  3.2A

         200-240VAC 1.6A

                           50/60 Hz

Output +5V-------30A

 

I just want to make sure I know what they are. Also on the site ProDCtoDC.com, can you supply a part number or URL so I can make sure I am looking at the right converter?

 

Thanks!

It seems your supply is indeed 5v at 30 amps and not 12v at 12.5 amps.

 

You won't be able to use DC-DC converters with that supply, at least not the normal buck type ones. 

 

I looked at Ray's ad again and it still has specs for two different voltages.. 5 and 12.. But yours is 5v from the info you just posted. 

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Ron, your such an artsy fartsy fellow. :P:D great art work to explain.

 

Plasma, I was just about to question your support for the DC to DC converters. But I see that you and the company worked together to improve their product.

 

As for me, I like to keep things simple (KISS). But if I ever do get into a project like yours. I might find myself having to go that way with the DC to DC. Glad to hear your endorsement of their revised product.

Hey Sir Max,

 

It turns out they said they never received the pictures and video I sent them.. (In China, could be true).  So I sent them yet another email since I have been trying to post my opinion of their product on their web site ratings.. they answered me (surprised) saying they don't really have a web master and that the rating doesn't work.. they also say started asking about the situation.   I sent them the video again and this time they got it.  Showed it to their engineer who promptly figured out what I have been trying to tell them.  They apologized all over the place and said now they understood what I was trying to tell them... they also told me the fix.  I appears there is a sheet of insulator that goes down before potting and it seems to be moving during the potting process.  They have fixed the issue according to the eng. 

 

I have had no issue (save one) with any of the ones that are working, and they hold very tight spec, only the ones that were internally grounded caused me grief. So the design is sound, just the process needed fixing.. I hope my frustrations will help more of us in the long term..  So now I do recommend the product. 

 

Try the converters Max, you will love the result and how easy it makes the pixel power wiring.. I am now making mini trees that are 5v and every one gets its own converter..I will string a single pair of wires with 24v and tap off where ever I need it.   I have about 50 of the 24v water proof UL listed power supplies left so I am set for Low Voltage power, I just need to order more converters now. 

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@plasma, I still need to get more power supplies and the ones I bought form Ray can be used elsewhere in my display, Do you have a power supply you recommend and the Dc-Dc-converter? URL's to these products would be great

 

Thanks!

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Plasma,

 

I have never played with DC to DC converters. And in this case I believe you called it buck down? Ok lets say I have 3 strips of 5V rated at 6A each with all 3 LED turned on at same time. Mind you I am pulling numbers out of the air. OK so that would be 18A at 5V. So my 24V supply would need 18A also or would it be something less?

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Sir Max,

 

Yes, buck converters are very common.  They usually have a range of input voltages.  The ones I use are 9-35v if I remember correctly. 

 

5v x 18 amps = 90 watts as you already know.  So you would need a 24v supply that was able to output about 90 watts or roughly 3.75amps.. You do need to add a bit for conversion loss, but only about 5-7% I think.  I would guesstimate off the top of my head that a 100 watt supply would work fine. 

 

So the wire size needed from the 24v supply would be pretty small as you can see.  The less voltage you drop in the 24v line the less total power that is burned up in heat.. but unless you used something really small that has a lot of resistance, it would be fairly insignificant..   I am thinking #16 up to 50' from the 24v supply... I used #14 on the Plasma Icicles and it fed the entire house from a 240 watt supply.  I had about 15-20 converters on that supply..

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Prof. Plasma,

 

I have yet to feel the flats of a saber on my shoulders. But thanks for knighting me. ;)

 

So, if I am reading this right. These DC to DC converters, not only convert the voltage. But they also convert the amps along with the voltage. I know that this is what transformers do with an A.C. voltage. But was not aware of any device that does this with D.C. voltages. Are these converters an inverter and converter in one? Another way of saying this, is, is there a D.C. chopper that is then transformed and converted back to DC voltage.

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