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I have this power supply:

enter image description here

And this, which has 2 wires coming out:

enter image description here

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  • \$\begingroup\$ Get a power supply that doesn't need a ground wire. 12V 1A power supplies are literally everywhere. Almost as common as 5V 1A. \$\endgroup\$ – Passerby Jan 19 '16 at 17:21
  • \$\begingroup\$ @Passerby but what if I connect those 2 wires without the ground wire to the power supply? \$\endgroup\$ – Giancarlo Jan 19 '16 at 17:27
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It will work but you are bypassing one safety mechanism. In case of a failure, the metal housing of the power supply will be at the mains potential. If someone touches it can be lethal. Don't do it!

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  • \$\begingroup\$ I don't understand what do you mean by failure? can you explain? \$\endgroup\$ – Giancarlo Jan 19 '16 at 17:35
  • \$\begingroup\$ Wire falling off, insulation breakdown, etc. There may be high-voltage devices attached to heatsinks attached to the case. These have very thin insulation layers and if they breakdown the heatsink and case will go live. With a proper earth connection the high current will blow the fuse and remove power, protecting you. Without an earth connection the case will go live, possibly killing you or someone else. You may also find that the device you are powering goes live. As @Hagah says, "Don't do it!". \$\endgroup\$ – Transistor Jan 19 '16 at 17:46
  • \$\begingroup\$ @transistor what if it is encased in a wooden box, I'm basically making a light pad to photograph negatives. \$\endgroup\$ – Giancarlo Jan 19 '16 at 19:21
  • \$\begingroup\$ And what if the insulation breaks down and the low-voltage side goes live? Why not do the right thing and earth the power supply as the manufacturer intended? \$\endgroup\$ – Transistor Jan 19 '16 at 19:32
  • \$\begingroup\$ Nothing to add on the words of @transistor. The wooden box will not help you, there is always the chance that somebody opens it. Buy the right source or use the one you have correctly with good earth connection. \$\endgroup\$ – Hagah Jan 20 '16 at 7:34

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