Author Topic: Power Injection question for 5 volt using a 12 volt power supply with buck  (Read 406 times)

Offline kryptic

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Question 1 : Hello  my question is when using a 12 volt power supply with a buck down converter for getting the power down to 5 volts. Do I have to also use a buck converter on the ground wire from the power supply injecting the ground to the string.
What is the best gauge of injection wire to use for medium size distances.


I have read some posts and the wiki on this topic but it doesn't answer the converting from 12 to 5 volt using a buck converter or step down for the injection process.
I know that the power and ground leads going to the string from the Falcon F4v3  power need to be disconnected from the point of injection. I see where some people leave some of the power and ground wires from the controller power supply connected and then add injection but i am not wanting to risk take at this point.


Question 2: what is a decent size of wire to run for data only to my 4th output its about 70' from string location to the Falcon F4v3 location I will have to run power from an inside power supply through a hole in the structure due to no exterior power boxes.




Offline AAH

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  Your description is a bit cryptic so I'm unsure what you mean by "some people leave some of the power and ground wires". You'll need the input ground to the buck to be connected back to the pixel controller. From the pixel controller you run ground and data out to where the buck converter is. At this point the pixels get connected to that data, the 5V and the ground coming from the buck converter.  Wire gauge is pretty much entirely controlled by current and distance. The number of pixels that you're wanting to power and the distance governs the voltage drop that you will have and that should typically be limited to around 10% at full load. For data only there is "no" current so the wire gauge isn't important. Cat 5 cable with 7 cores as ground and 1 as data is as good as anything for running data only.
 

Offline scamper

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Not 100% sure what you are asking, but if you are asking if you need to run an earth wire to the buck converter and then on to the display, then yes. Voltage is only a potential difference between 2 points.  The ground or earth wire is generally zero volts, so the potential difference between that and the positive wire is what gives you the voltage. This is also why you should connect earth wires from different supplies together as if you had one of the earths "floating' say around 1v and you were using 5v leds, then you have only 4v potential difference across them.


How many pixels are you running off these buck converters? If it is only a few then fine, but if you intend to run a lot, I would look at getting a 5v power supply. The loss involved in dropping the voltage and  also the power you can draw through a buck converter is going to limit the amount of led's you can run.

 

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