Servos

Installation

Don't forget to use the rubber grommets and the brass eyelets (ferrules) that come with the servo packs! After that, mount these however you like and rest easy knowing that vibrations can no longer hurt you (hopefully). Vibrations will eventually destroy the servo so it is good idea to mount it correctly. And obviously vibrations to the mounting area will cause vibrations over your entire part as well. Everybody knows vibrations makes everything so it is good to avoid that.

1. Make sure flange portion of the ferrule (the larger flat area) faces down and not up. In other words, the flange should face the backside of the servo.
2. When putting screws in, make sure the screws just touch the flange, do not over tighten it. The servo should be able to wiggle between the rubber.
3. Make sure any other part of the servo does not touch anything else, as that causes vibrations and will ruin your beautiful setup.

Power

Powering a single servo is pretty easy, but things get harder if there are multiple servos. The main issue is current, servos draw a lot of current when it peaks, and a single power supply is usually unable to handle this. Therefore you need an external power supply with enough current to power all of the servos combined. And everythnig must connect to the ground line along with the controller (all together).

For the current, you should consider the stall current (current of motor under maximum load or locked) and not idle current which is the current when it is not moving. Generally

• micro servos (9g size): stall current of ~0.8-1.2 A, idle current of ~0.1 A
• standard servos (20-30g size): stall current of ~1.5-2.5 A, idle current of ~0.2 A
• high-torque or large servos: stall current of around 3-6 A

You would want some extra current of course, like with all things in life. 20% or more margin of safety should be plenty. For the power supply, a LiPo battery is generally good when paired with a UBEC (Universal Battery Elimination Circuit) for voltage regulation (this is required or the high voltage will destroy the servos). Can also use an AC-DC switching power supply, but make sure to add short-circuit and overload protection.

Make sure the servos get power from the same point (star connection) and not daisy chaining. A power distribution board (PDB) helps a lot with this: battery to PDB to every servo. Make sure to use an external power supply and not the 5V power supply out of a microcontroller, since the current is too small (0.5-1 A).

You can use capacitors to suppress voltage spikes, since servos are motors which are inductors. Inductive loads thus create voltage spikes and sags, which can stabilized with capacitors. You can use

• a large capacitor across the positive and negative terminals of the PDB.
• a smaller capacitor close to each servo's power pins

This is optional, but is really helpful, especially when using a battery pack to power servos.