Let's Make Robots!

Holy Servo's Batman!

So I guess today is Day 1 of my impending doom.  I ordered my Diecimila (or however the heck you spell it) along with a solderless breadboard for it.  I also went ahead and bought myself a servo at Hobby Town USA since it is just down the road from my house.  I got the HS-311 Standard Servo.  I have no clue if this is a good, average, or crappy servo.  I figured it would do for learning processes and if it isn't applicible to a bot to start with, who's to say I can't find a use for it eventually.  So basically the point of this post is two-fold.


1) I want to make sure I actually know something, so i labeled the parts that came with it, as you can see in the image.  I believe they are labeled right, as I went off of assumptions and hunches.  If I am wrong anywhere, lemme know.


2) I need to start to understand what all this gibbereish on the back of the pack means, so I am turning to some people who can answer it for me, since my google searches were fruitless.


Specifications of the HS-311

  • One Resin Bushing
  • Hitec Custom I.C.
  • Operating Speed: 0.19sec/60° AT 4.8Volt
  • Output Torque: 3.0kg-cm(42oz-in) AT 4.8Volt
  • Weight: 43g(1.5oz)
  • Size: 40 X 20 X 37mm(1.57 X 0.78 X 1.43)"

Now obviously I don't need help with the Weight and Size, I just included them to be complete.  I am going to go ahead and put here what I think the entries mean, and you all can correct me as you see fit.


  • One Resin Bushing - I have no clue, seriously.
  • Hitech Custom I.C. - See above...
  • Operating Speed - I think that this means that at 4.8 Volts it can make a 60° rotation in 0.19 seconds
  • Output Torque - Following my above logic, then that would mean that at 4.8 Volts it can push (if set up to do so) something up to 42 oz.
So yeah, That's what I think...anyone willing to learn me better?
Servo's Labeled Right At Least!435.42 KB

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well, what exactly do you plan do do with the servo...cause for the most part.  I don't think the speed or anything will really matter in the end as well. I just say this due to the fact that I have at least 7 different servos of various types and sizes and the only thing that matters is if it's a continuous rotation or not....

Torque will matter if you plan on moving heavy stuff or if it's going to have a lot of resistance...which, if you're just rotating the direction of a sensor is pointing....really won't matter. 

Currently, that's about the extent of what I want it to do, although until I get the sensor, I think it might be moving coins and random lightweight things I put on it, just so I have something to do.  Eventually I plan on using a similar servo (maybe even this one, depending) to make a remote controlled Airsoft Turret for my mom to take into the office for pranks and such (oddly enough).

about torque

Output Torque: 3.0kg-cm(42oz-in) AT 4.8Volt means that this device can hold or even move a weight of up to 3 kg when suspended from a 1 cm arm (measured from the center of the shaft to the suspension point). Appearantly that converts to a weight of 42 oz dangling from a 1 inch arm.

Think you've heard this before? Well probably you did. A lever also has an arm and a load. So a 42oz-in lever/servo could also lift 21 oz from a 2 inch arm. Or 84 oz from a half inch arm. Etcetera.

Of course servos are not always about lifting stuff. Sometimes the force is from friction in a wheel, or from accelerating a mass. Too many people still think of force as "weight". But real scientists (sounds pedantic huh?) use the Newton as the unit for force.

Basicly your servo can provide a 30 Newton force x a .01 meter arm. Your torque would be written as .3 Nm.

  • resin bushing - the top part of the servo case where the output is and you attach the horn to is made of resin, slick and tough. Some servos will have nylon, some will have a ball bearing, some might have 2 ball bearings
  • custom IC - there used to be only a couple of ICs that had the feedback circuit and compared it to the input pulse to drive the motor. Hitec has their own ASIC (application specific IC) used in their servos, as other companies probably do too
  • operating speed - you got it, the time to move 60 degrees. servos are usually rated for 6 volts too, and some folks drive them even higher voltages. About 7.2 is my limit.
  • ouput torque - as has been stated, the 42 oz-in, means 42 oz at one inch away from the center of the output gear
Cool, it's good to know that I am actually learning this stuff and not just really good at BSing my way through it.