I'm testing my arduino with servos, and my sg90 works fine for testing purpouses.

I would like to use something stronger, and my father (that in the 80s used to work with RC autos) gave me this old but promising servo.

enter image description here

I know I can't supply power with arduino if I want it to survive august, and I know all the servos work around 4.8-6v.

The problem is I can't really find any datasheet for this servo, and I would like to know at least the current drain to dimension my external power supply (or how can I misure it. All the wires are black, making it even harder).


This appears to be a scan of an old catalog.

It lists the SM-351, and says it uses 100mA.

That appears to be in French. I can't read French, but the designations are pretty easy to puzzle out.

As for the connections, they seem to be pretty standard.

Have a look here for examples. Ignore the colors, and look at where the wires are in the connector. Postive is in the middle, ground is one of the others. Also, you can just buy the fitting connector with wires - they are color coded.

Regarding the low current consumption:

The servo might be intended for use with a higher voltage. The catalog unfortunately doesn't list the operating voltage.

@Hayman found a picture that implies that the SM351 runs on 4.8V like most common servos.

  • \$\begingroup\$ Seems strange to me for the 100mA! Classic sg90 drain a maximum of 250mA and they really seem plastic toys when compared to these! I'll give it a try and see! Thanks for the clear answer man. \$\endgroup\$ – lateralus Aug 23 '16 at 10:59
  • \$\begingroup\$ Are you sure this isn't a 12V device? This could explain the "low" 100mA drain. \$\endgroup\$ – user72833 Aug 23 '16 at 11:52
  • \$\begingroup\$ @Tibo: That would explain it. Unfortunately, that catalog doesn't list the operating voltage. \$\endgroup\$ – JRE Aug 23 '16 at 11:57
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    \$\begingroup\$ @Tibo I had a look around and found this picture. Looks like it's powered by 4 x AA \$\endgroup\$ – Doodle Aug 23 '16 at 12:16
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    \$\begingroup\$ That is probably a nominal current. Loaded/stall current would be much higher. A decent power supply beyond on-hand AA cells may cost more than the servo is worth. \$\endgroup\$ – Chris Stratton Aug 23 '16 at 13:23

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