I've been researching various websites on all of my questions and have found answers to many of them but I am also finding conflicting answers for some of them. I've read that electricity is something that is very dangerous when you are in contact with the main and that is what I think I am doing so I wanted to verify my setup and have all my questions answered so I can be safe while handling these.

My setup basically starts with an old wire that I found around the house. This is a standard 3 prong US plug which I'm assuming was from some laptop charger. What I've read online is that I want to cut the end off (the part circled in purple) and it'll have 3 wires which I will connect to the power supply. (If there are any cheap, fast, and safe alternatives that allow me to not cut the end off please let me know)


This is the power supply I've ordered. From what I've read I am assuming that when I cut the end off the wire I will reveal 3 wires, black, white, and green. Black goes into the L, white goes in N, and green goes into ground which is the one next to N with the lines. Now I can plug it in to test if it works and everything should be safe and I can unplug and cover that entire section with some black electrical tape.

Power supply

After hooking up the wires I can hook the power supply to the arduino and LED strip. I read that I needed a common ground, but I don't know what that really means. I'm assuming I do since everything goes to the power supply which is grounded through the 3rd prong on the wire, but if I'm wrong please let me know. This is the arduino nano I am using. I'm going to use one of the V+ ports from the power supply and have a 20AWG wire run it to the 5v pin and then the V- is going to have a 20AWG wire ran to the GND pin. These will be soldered into place and then covered with electrical tape. Then there will be a 20AWG wire going from the D3 pin to the DATA pin of the WS2812 LED strip. Now from the power supply there are still unused V+ and V-. I will put a 20AWG wire into the V+ and it will be soldered into the 5v+ copper part of the LED strip and and GND of the LED strip will be connected to the V- of the power supply that is unused. Then I will wrap this with electrical tape.

enter image description here

Thank you for reading this and please let me know if this setup is safe. Also let me know if this has a common ground. If it does, does that mean V- and GND are essentially the same? Also is it safe for the arduino and my computer to plug the arduino into my computer via USB to upload code while its being powered by the power supply?

Sorry for the lengthy question, but thanks in advance for any answers!

  • \$\begingroup\$ Two things. 1. Common ground means that the ground or negative side of each board is connected together and to the V- terminal of the PS. It has nothing to do with the AC ground or earth connection. 2. You may or may not find the wires in the AC cord are color coded as you expect as it is not designed for someone to take apart. You may need to buy a cord which ends in separate wires. \$\endgroup\$
    – DoxyLover
    Commented Dec 31, 2018 at 10:36

1 Answer 1


Sounds OK.

Things to pay attention to

  • Neat connections
  • EMI noise from floating 0V sources
  • Comm. Errors
  • strain relief for AC cord ( plastic clamp to nearest frame screw)

How confident are you in attaching twisted stranded wire around closely spaced screws to avoid stray strands shorting out after getting neglected or yanked?

Normally they use crimp lugs for AC input or you can solder tin the wire enough to wick a bit under the insulation then bend into a curl CW under screwhead. Crimp lugs are cheap but simple skill requires crimping both insulation and wire so it is not exposed and survives a 2kg pull test easily.

enter image description here

Murphy's Law

Sometimes floating SMPS DC output that have common mode noise may cause USB serial port comm errors from noise leakage on USB to an earth grounded tower YET not to an earth grounded laptop since both are floating. But it also depends they come from different AC outlets. That's what I discovered visiting the ECE lab at U of T. One fix is to add a cap of 1nf to 10nF between EARTH GND and V-= 0V to bypass some SMPS CM noise issues that leak thru to the DC side..

  • \$\begingroup\$ I'm very sorry but I'm new to electronics. I was wondering what you meant with this line "Normally they use crimp lugs for AC input or you can solder tin the wire enough to wick a bit under the insulation then bend into a curl CW under screwhead." I'm new so I'm not super comfortable with anything but from what I saw when I googled twisted stranded wire, it just seems like you twist the wire together which seems relatively easy. Thank you so much for your help! \$\endgroup\$
    – Deflector
    Commented Dec 31, 2018 at 1:27
  • \$\begingroup\$ What line?..... \$\endgroup\$ Commented Dec 31, 2018 at 1:28
  • \$\begingroup\$ Sorry, I pressed enter to make a new line and it posted, I've edited the previous comment I believe. \$\endgroup\$
    – Deflector
    Commented Dec 31, 2018 at 1:30
  • \$\begingroup\$ I didn't want to assume the easy connection might have an "oops" on the wire twist with loose strands, with no strain relief, so there are better ways thespruce.com/tinning-stranded-electrical-wires-1152893 \$\endgroup\$ Commented Dec 31, 2018 at 1:59

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