Last time, I gave a basic introduction to the simple pulse interface for sending commands to servos. In this post, I want to explore some of the details and ramifications of the servo interface in a bit more depth. I’ll be using the Mini Maestro 12-channel servo controller, which offers a lot of servo control flexibility, and a current probe with my oscilloscope to illustrate servos’ responses. Continued…

This excellent guide from C.I.r.E. (Club de Informática, robótica y Electrónica) shows in detail how to build a fast (> 2 m/s) line-following robot from scratch, and it makes use of a number of Pololu products.

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This project by Kazuhiro Ouchi (in Japanese) shows a 3pi robot with an ARM mbed controlled by Bluetooth keyboard.

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So far, I have been talking about servos largely from the perspective of their typical use. While I hope I have provided a decent foundation about their intended use and some idea of what is inside a servo, these are things you could learn from hobby stores and taking apart a few servos. Today, I want to move on to a discussion of the electrical characteristics of servos, with the control interface as the primary topic. From the servo manufacturers’ perspective, the control signal can be an internal detail, so discussing it means we are moving on to a realm that is less officially documented. I will try to keep things general and back up my claims a bit where practical, but some details might not apply to all servos. Continued…

We found this robot pictured on the Adafruit forums driving through some snow. It was made with a TReX, a 4WD Wild Thumper, and a Boarduino.

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Now that the cat’s out of the bag about RC servos having motors inside (it was a very transparent bag), it’s appropriate to emphasize that servos are not “servo motors” and that “servo” is not short for “servomotor”. Servo is short for “servomechanism”, whereas servo motors are motors intended to be used in servos. It’s important to understand the distinction because we should care about names and communicating well; making the distinction between the terms will also help emphasize why servos are so special. Continued…

A customer recently wrote: “I think you really need to add comments from users under each product (like sparkfun does). Makes it easy to review good/bad about a project and ask a question not in docs.” I rejected the idea when some of our developers pushed for comments on our web site a few years ago, and upon reconsideration, I am still firm in my opposition. Continued…

Having introduced servos and their role in a typical hobby radio control application, I will now focus on the servo itself: its parts, what is inside, and a bit of how it works. We will look at a few different servos along the way to better understand what servos have in common and how they differ. Continued…

Hobby servos are small, modular actuators developed by the radio control (RC) hobby industry for remote manipulation of everything from miniature boat rudders and car steering linkages to model airplane flaps and toy parachutist release mechanisms. The RC market is large and competitive, which has led to a proliferation of servos that have been optimized for characteristics including size, speed, torque, and price. This modularity, variety, ubiquity and cost-effectiveness of servos make them attractive generic actuators for small robots and other electromechanical systems. Continued…

Two ShiftBrites controlled by Mini Maestros power a flashlight capable of displaying one million colors with many interesting modes of operation. For more details, see Reed Kimble’s forum post: My Absurd Project – The One-Million-Color Flashlight!.

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