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I have a generic 5V 10A switching power supply with screw terminals, that looks kind-of like this:

Power supply

Is it safe to use the output from here to drive the Pi by cutting a USB cable and connecting the power wires to the terminals? I am already using this power supply to power a set of LED lights (similar to these) and I want to avoid needing an extra power supply just for the RPi if I can help it.

Is there anything in particular that I need to be careful about when doing this, other than accidentally crossing the wires?

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I have used a 12v version of this and then used a linear regulator to drop it down to 5v.

It worked fine for driving the Pi but because it is a switched mode power supply the output is quite "noisy" and even putting it through the linear regulator I still had the noise. I was using the Pi to switch camera outputs and the resulting picture had lots of lines of interference on it.

  • I'm curious about the noise you mention. My DC power supply experience is limited and I was having a tough time assessing why my 5v switch mode PS seemed to be affecting my 3D printer connected to my RP3. Any time I'd send a Gcode command to the Arduino (running Marlin), the USB connection would reset and I'd have to restart the RP for it to properly connect again. I was trying to filter out irregular voltage, but I ended up creating another problem, it would seem. – Erutan409 Nov 2 '17 at 21:02
  • The average voltage will be fine but the noise I was seeing was related to the switching frequency of the power supply (say 60kHz). Because it had such a fast edge to it, my grounding/filtering wasn't adequate and because it wasn't synchronized to the video camera I got the interference.For the digital case you have it might be more down to the ability of the power supply to supply the necessary current under demand. – Kev Scott Nov 10 '18 at 18:44
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Kind of overkill, but as long as it is 5v it should work. And skip the USB hack. Power through the GPIO connections.

See: Safest way to power a hungry Wifi adapter and the Pi from a single 5V source

and

Suitable power supply for DC power through GPIO

Edit: The USB hack will work. I just think the GPIO pins are easier to connect to.

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