I just started my first PCB and I have a question. I want to use two servos (SG90s) and a 5 V regulator powered from a 7.4 V battery.

After all my calculations the temperature that is dissipated is 160°C, but that's the thing I can not understand. My first prototype that I made was done using the same servos and an Arduino Nano, and I didn't have any problem with overheating or something like that. Are my calculations bad or will my LM1117 be fried?

This is my configuration:

enter image description here

My calculations:

enter image description here

  • 2
    \$\begingroup\$ How did you arrive at 160 degrees? How much power do you expect the servos to draw? \$\endgroup\$
    – JRE
    Commented Aug 13, 2022 at 21:05
  • 1
    \$\begingroup\$ You can't calculate temperature without having some information on heatsinking, so, where did you get 160 °C from? \$\endgroup\$
    – Hearth
    Commented Aug 13, 2022 at 22:00
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    \$\begingroup\$ We don't know how you ended up with 160 degrees C. It would help to see what formulas you used and what values you plugged in to come up with 160. \$\endgroup\$
    – Justme
    Commented Aug 13, 2022 at 22:09
  • \$\begingroup\$ Hi! I will post my calculations here. imgur.com/fI6Xbjv In fact i want to use those SG90S servos to move a 3D printed device using a PID. Link for SG90S: smart-prototyping.com/MG90S-9g-metal-gear-digital-servo.html \$\endgroup\$
    – GMW
    Commented Aug 14, 2022 at 8:20

1 Answer 1


Those wee RC servos don't draw anything like 550mA on a continuous basis under normal conditions. If they did, they'd quickly burn up. They can, however, draw more than 550mA when stalled or when starting. From this website:

enter image description here

So if they're lightly loading and running 10% of the time, the average current might be more like 15mA than 550mA.


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