Engage Your Brain (Page 7)

A blog by Pololu president Jan Malášek. For more information, please read the first post.

Servo control interface in detail

Posted by Jan on 9 February 2011
Servo control interface in detail

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…

Electrical characteristics of servos and introduction to the servo control interface

Posted by Jan on 3 February 2011
Electrical characteristics of servos and introduction to the servo control interface

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…

Servo, servo motor, servomotor (definitely not server)

Posted by Jan on 28 January 2011
Servo, servo motor, servomotor (definitely not server)

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…

Why we don't have comments on our product pages

Posted by Jan on 25 January 2011
Why we don't have comments on our product pages

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…

Gettin' all up in your servos

Posted by Jan on 21 January 2011
Gettin' all up in your servos

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…

Introduction to servos

Posted by Jan on 14 January 2011
Introduction to servos

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…

Introduction to an introduction to servos

Posted by Jan on 7 January 2011
Introduction to an introduction to servos

My last post about force and torque got kind of long, prompting some suggestions that I break it up into two separate posts. I didn’t do it because my sentiments about units and the common confusion of weight and mass applied to both topics. I want to move on to a thorough discussion of hobby servos, which is broad enough of a topic that it definitely merits a breakdown into multiple posts. That got me thinking about the order in which to present the material. So, this post is mostly about organizing and presenting information and not really about servos. Continued…

Force and torque

Posted by Jan on 31 December 2010
Force and torque

I got a few private requests for more information about torque after my post on units, and since torque is relevant to the next few posts I want to make about servos, I’ll try to explain torque a bit more today. Torque is intimately connected to force, so we’ll start with a review of Newton’s laws of motion. You should know some basic calculus to really understand these concepts, but getting into that is beyond the scope of this post; I hope I hit the right level of simplification to provide some useful knowledge to those who have some basic intuitive mechanical sense but have not taken, or have forgotten, basic physics courses. Continued…

More LEDs

Posted by Jan on 23 December 2010
More LEDs

With Christmas just a few days away, and having just discussed a single LED circuit and simple parallel circuits, I’d like to make a few comments about using multiple LEDs. I’m still talking about basic LEDs, and not too many of them; for specialized LEDs or large arrays, there are all kinds of chips designed just for that. Continued…

Parallel circuits

Posted by Jan on 17 December 2010
Parallel circuits

If you have a limited or informal electronics education, parallel circuits might be the kind of topic you glossed over or have forgotten about. After all, parallel circuits sounds like boring theory, and you want to get to the fun stuff. But, banging your head over a simple system that you think should just work isn’t much fun, and you can save yourself a lot of grief with a bit of awareness about the potential differences between a schematic and a physical circuit. Also, I’m a proponent of learning fundamentals and trying to really understand things, so we’ll start with a bit of the basic theory. Continued…

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