Servo SG90

Hi, I guess several people are using the SG90 servo. The docs I have state supply voltage 5V and signal levels of 5V too. Does it also work with 3.3V from a prop pin?


  • If the logic threshold is below 3.3v then I think it would.
  • If the logic threshold is below 3.3v then I think it would.

    That is what I wanted to know, because it does not work for me.
  • ercoerco Posts: 19,720
    Well now I have to see if I have an SG90 servo. Of course, what's a "real" Tower Pro servo is up or debate. I buy a lot of dollar servos on ebay, and I'm pretty sure some of them have that sticker on them.

    I would think most servos should operate from a 3.3V control signal. What's the supply voltage to your servos, rbehm? Please don't say 3.3V...!
  • ercoerco Posts: 19,720
    edited 2019-07-23 - 21:05:23
    It sure should work. I took a cheapie servo tester running at 5V and split the control signal in half with a voltage divider (two 1K resistors), so it was only getting a 2.5V control signal. Again, mine is a cheap $1 Ebay servo marked "SG90", but it may be a clone (or yours may be a clone).

    Of course the servo was powered by 5V. As I already mentioned, don't expect a servo to run off of a 3.3V supply voltage. Also, servos need a LOT of current, so they need a hefty supply with lots of capacity. Often they are connected directly to the batteries, no regulator in between, provided the voltage is right (3-4 alkaline cells, for instance). A lot of people get burned by using old batteries. Always check your battery voltage, and don't use anything but new alkalines. Cheap "heavy duty" batteries at dollar stores are a joke. "Ideal for low-drain applications" = Stay Away!
    1440 x 2560 - 1M
  • You could use a 3.3V pin to drive a transistor to supply the 5V signal. I would use a 4.7 ohm resistor to protect my pin.
  • rbehmrbehm Posts: 77
    edited 2019-07-24 - 14:01:58
    Ok, with a 2n2222 as a level shifter it works now.
    I am sure I had it working without that a while ago. Even two servos. But now it only works with 5V levels. Yes, I have taken care of adapting for the inverted signals.

    If I get hold of that guy who changed the laws of physics in my lab.
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