I'm building a data acquisition system that needs to power sensors and a high voltage contactor at 24Vdc, 12Vdc, and 5Vdc. After reading another post, it seems it is best to use separate AC-DC power supplies for each output voltage. Therefore, I plan to wire my power supplies to my AC output as seen in my simplified wiring diagram below:

Wiring Diagram

Should I be concerned about how much current is being drawn from my power outlet? Is there anything I could add to make my system safer? I've received mixed comments about using two separate AC outlet connections instead of one to power my power supplies, but I'm aiming to have only one AC power cable if all at possible. Any tips are appreciated!

  • 1
    \$\begingroup\$ Should I be concerned about how much current is being drawn from my power outlet - not with the consumption stated on your diagram. Assuming you have somewhat standard outlets of course. \$\endgroup\$
    – Eugene Sh.
    Sep 14 at 20:20
  • \$\begingroup\$ I live in the US, so a simple search tells me 15A. Have several co-workers telling me otherwise, 10A to be specific. Seems low to me? \$\endgroup\$
    – HighFives
    Sep 14 at 20:24
  • \$\begingroup\$ Do you know how to calculate the overall AC current from 120VAC given your data? From my calculation it will be slightly more than just 1A \$\endgroup\$
    – Eugene Sh.
    Sep 14 at 20:27
  • \$\begingroup\$ use a power bar \$\endgroup\$
    – jsotola
    Sep 14 at 20:29
  • \$\begingroup\$ Is this a rack-mounted station? Companies make Power Distribution Units for this purpose. Years ago, we put outlet strips inside test stations, but that is not per code. \$\endgroup\$
    – Mattman944
    Sep 14 at 20:31

1 Answer 1


The overall power consumption of your devices is about (multiply voltage and current)

15 W + 60 W + 60 W + 48 W = 183 W

There will be additional conversion losses for the power supplies.

Let's assume 240 W of total power consumption.

That will take 2 Amps of current from the 120 V wall outlet.

No matter if the wall outlet gives you 10 or 15 Amps, you will be safe drawing only 2 Amps.

Only one wall plug.

  • \$\begingroup\$ It will also save you headaches/the occasional explosion from connecting two or more independent power supplies' grounds together. \$\endgroup\$
    – vir
    Sep 14 at 20:57
  • \$\begingroup\$ The wattages you calculated are using the power supplies' output voltage/current. Shouldn't we use their input voltage/current values instead? For example, the 5V power supply has current/voltage inputs of 0.55A 115Vac, therefore 143 W. Do you agree? \$\endgroup\$
    – HighFives
    Sep 14 at 23:22
  • \$\begingroup\$ I don't believe that a 3 A 5 V power supply will draw that much power. I assumed about 80% efficiency and rounded to 240 W to compensate for the actual power taken. 143 W in for 15 W out would be the most inefficient power supply I've ever heard of. The value you mentioned is probably the maximum input current – for whatever reason it may be that high. Apart from that – sure, calculate the power actually drawn from the power plug, not the power going to the devices. Edit: BTW 0.55 A 115 Vac is 63 W, not 143 W. \$\endgroup\$
    – ChristophK
    Sep 16 at 17:13

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