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I got my hands on a few Tower Pro SG90 9G servos but cannot find their schematics or datasheet anywhere (besides that link).

I have the following concerns:

  • Looks like they're rated for 4.8V, but will they tolerate a 5V supply?
  • How do I determine the current they require, in amps, mA, etc.?
  • There's 3 wires: brown, red & yellow-orange, what do each of these guys do?
    • If I had to guess I'd say that red is power, another one is direction, and another one is the position to rotate to
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Regarding the voltage, the Amazon listing for this servo gives the operating voltage range to be 3.0 to 7.2V, so it should accept 5V no problem.

Regarding the current draw, on the user questions section of the same page, one user stated that these servos drew between 750 - 1000mA when fully loaded.

Regarding the wiring, PCB has a great article on servos that says the wiring would go generally how you would think - red is (+), black or brown is (-), and the other wire is signal. It says that Tower servos use red, black, and white wires.

Hope this helps!

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  • $\begingroup$ For anyone who is then subsequently wondering "OK, well then how do I know what signals to fire across the signal wire to drive the servo?!?", read this. $\endgroup$
    – smeeb
    Jun 11 '15 at 1:15
  • $\begingroup$ Yeah, as mentioned in the comments to the question you linked, servos are all relatively generic in that servo manufacturers have done a terrific job of standardizing the physical and electronic interface. In the article I linked in my answer, from PCB heaven, they also state most servos' full range is in the 1-2ms range, and they give common frequencies for analog and digital servos, AND they give a circuit that can be used to drive the servo with no micro controller. It really is worth reading. $\endgroup$
    – Chuck
    Jun 11 '15 at 1:40
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The red one is Vcc+ (positive) generally 5-6V, brown is ground and yellow-orange is the signal, usually a pulse-width modulated signal (PWM). The current depends on the load driven. For no load conditions its usually as low as 500mA when fully loaded may require up to 1A. Good Luck and cheers

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According to this datasheet(1), the red and brown wires are power and ground, while the orange wire is the PWM control (as Vinokanth Velu suggested).

The PWM line expects a pulse every 20ms. If the pulse is 1.5ms wide, the SG90 will move towards the midpoint of its 180 degree travel (position 0). If the pulse is 2ms, then it will move all the way to the right (position 90), while a pulse of 1ms, will move it all the way to the left (position -90).

The deadband determines the minimum move you can specify, 10us (as suggested by this datasheet) would be around 1.8 degrees, 1us (as the manufacturer specifies) would be 0.18 degrees.

As for how much power it will draw, that depends on what you are asking it to do. Holding position with no force will take very little power, swinging from one extreme to the other and back with the full 1.80 kg-cm force would take significantly more.

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There are datasheets out there, but none seem to be manufacturers' original, which make them no more worth than toilet paper. What signal protocol(s) does it accept, does it hold presets, for example.

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    $\begingroup$ Welcome to robotics Rahere, but on Stack exchange answers need to answer the question. Take a look at How to Answer and tour for more information on how stack exchange works. $\endgroup$
    – Mark Booth
    Aug 14 '15 at 11:51

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