Engage Your Brain

We expect to release a simple carrier for ST’s new LPS331AP pressure sensor this week. While testing and writing example programs for the sensor, one of our engineers, Kevin, came up with a nice demonstration that calculates and displays the altitude on our Orangutan SVP robot controller. It was a beautiful spring day with great flying weather, so Paul and I took Kevin’s digital altimeter on a flight to Lake Havasu City, Arizona, to see how it compared to the altimeter in a plane. Continued…

I posted toward the end of last year about some new equipment we were adding to our manufacturing operations and said the best stuff was still coming. I and several others at Pololu have since had some more personal deliveries of the crying-all-night sort, which delayed my promised update. I still do not have the performance information I had hoped to have by now, but let’s at least look at what we got: Continued…

I sort of had a meeting with the governor of Nevada this morning. I’m posting some notes about it mostly for others at Pololu, but maybe it will be interesting to other small businesses in Las Vegas. I probably should have been more prepared for the meeting; I still don’t know much about who was there or what exactly happened or what the stakes were, so a lot of my descriptions are kind of vague. Continued…

As we head into what is traditionally a week of heavy discounting, I want to give a little update about some new equipment that will be a foundation for our long-term commitment both to lowering prices and increasing the quality and sophistication of our products. Plus, I figure these kinds of machines are fun for our customers to look at. Continued…

Starting with the move from our dorm to an apartment in Watertown, Massachusetts, Pololu has moved or expanded ten times. The most significant was our move to Las Vegas, which represented a commitment to doing this thing for real. This past Sunday was the 10-year anniversary of arriving in Las Vegas, so I figured I should commemorate it by putting up some old pictures. Continued…

As open-source hardware (OSHW) has become more prominent over the past five years or so, I have heard questions about where I or Pololu stand on the subject. Most recently, I got into a bit of a discussion with Phillip Torrone of Make and Adafruit on one of his blog posts, and his questions and subsequent interview pushed me to try to organize some of my thoughts about OSHW. Because there are many aspects to OSHW, I don’t have a simple conclusion like, “It’s great!” or “It’s the future!” or “Pololu will never release an OSHW product.”. I am skeptical of some of the claims by OSHW proponents and of the significance of the more organized aspects of the OSHW movement. However, what is going on is very significant to me because it affects Pololu’s business and involves issues I care about a lot, such as freedom, creating things, and education. Continued…

This post is an account of the difficulties I have had for the past four months in getting permits to run our equipment at our new location, which we moved to in December of 2011. I am writing this partly as notes for myself and others at Pololu, but the main point of sharing this is to warn and commiserate with other businesses having to deal with such problems and to give other readers some awareness of the real-world ramifications of the regulations much of the public seems all too eager to embrace. I still have a hard time believing we really had to go through all of the hassle and expense, so I am also hoping that some readers might point me to some resources so that I can avoid this in the future. I realize there is speculation and hearsay in my report, but I want to emphasize that my impressions are based on many vendors, contractors, public employees, and manufacturers: in all, I spoke to dozens of people about our experience. I will try to be as specific as practical without unnecessarily exposing individuals who were trying to be helpful to undue scrutiny. Continued…

Five months ago, I wrote that we “just finished a big facility expansion that was taking up a lot of my attention this year, so I have some more time now …” Well, that turned out to be wrong. It’s also been over a year since I started this blog, and so far, I am way behind my target of an article per week. It doesn’t help when I don’t post for four months, but some exciting stuff has happened in that time. Continued…

As I discussed in the introduction to servos, one of the consequences of hobby servos’ intended use is that rotation range is limited to about 180 degrees. In this post, I will talk about two exceptions to this general rule: continuous-rotation servos and multi-turn servos. Each of these products loses some features in return for increased rotational range, so none of them are the ideal actuators many would like them to be. There are some specialty servos developed for robot applications that get around the limitations, but those servos are not as standardized and do not really fit into the hobby servo category, so I am not going into any more detail on those beyond mentioning that they exist. Continued…

The Wixel Shield for Arduino that we released today represents a personal milestone because of what I did not do on it: the shield is the first electronic product made by Pololu that I did not design. That’s not to say I did not have some input on it or that other engineers here did not have substantial contributions to other products, but the Wixel Shield is a first because the basic product concept, the circuit design, and physical implementation (i.e. the PCB layout) were all done by someone else. We also just finished a big facility expansion that was taking up a lot of my attention this year, so I have some more time now to think about our design process and what it takes to go from a new idea to a finished product. Continued…

It is often desirable to control the speed and acceleration of hobby RC servos. Understanding your options can be confusing since there are various speeds involved, many similar terms are used, and the terms are not used consistently by different companies or end users. You might also have an idea of what you want your servo to do without knowing what to call it or how to describe it or how to implement it. To get a good understanding of what is going on, it is helpful to picture the position of your servo in relation to the commands you are sending it. A simple first attempt might look like this: Continued…

In this last article about generating pulses for hobby servo control, I will present what I think is the best solution to controlling many servos or controlling some servos while still leaving enough processing time to do other tasks. It’s not that easy to make this approach work well, so my recommendation in most cases is just to get one of our servo controllers, which use this technique. Continued…

So far, I have discussed a very simple circuit and a very simple microcontroller approach to generate the control pulses needed to control hobby servos. For some applications, those methods are sufficient, but we often want either to control many servos or to do something in addition to controlling servos, and that is when the limitations of the simple approaches and the demands of the servo interface become more apparent. In this post, I will move on to some more sophisticated techniques to generate servo control pulses. Continued…

Today, I want to discuss the microcontroller equivalent of the simple servo control circuit I presented last time. As I mentioned then, the circuit is about as simple as it can be, yet it requires eight components to arrive at a sub-optimal servo control waveform. Some of its deficiencies, such as the slow rise time of the pulses, can be addressed by slightly more advanced circuits that might implement an astable multivibrator using an integrated circuit such as the famous 555 timer. In terms of part count, the 555-based servo controller might be a bit better than the two-transistor approach, but the 555 has many transistors inside it. As long as we are comfortable categorizing a component with many transistors inside it as a single part, we might as well skip the 555 and go straight to a low pin-count microcontroller, which has thousands of transistors inside it and which will allow us to make a far superior, single-component servo controller. Continued…

For the last several posts, I have been writing about how hobby servos work and demonstrating the operation of devices made for controlling servos, such as RC receivers and serial servo controllers. That should have given you a good idea of the kinds of control signals we must create if we are to control servos with our own hardware. Today, I am moving on to the subject of controlling servos ourselves, and I will begin with a simple hardware approach. Continued…

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…

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…

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…

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…

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…

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…

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…

The simple LED circuit from last time is a great first circuit for everyone interested in electronics because it is so forgiving. If you connect something backwards, you probably won’t break anything, and otherwise, it should just work. However, that forgiving nature of the circuit can beguile newcomers into thinking everything is that simple, and though there are many web pages out there discussing the circuit, they usually do not address the abstractions and simplifications that are in play and why we can use them in this instance. So, that’s the topic for this post. Continued…

One of the simplest circuits you can build is an LED powered by a battery. Unfortunately, many people who think they know some electronics (and even multiple job interviewees with supposed electrical engineering degrees) cannot actually draw the schematic for the simple circuit or calculate the appropriate component values. Can you? Continued…

We should consider the general concept of abstraction in robotics a bit before moving on to more specific topics. Abstraction comes up a lot in computer science and programming, so I think people in that field are exposed to it early and often. Just about any program will have at least some user-made abstractions in it, be it a data structure or a subroutine, so programmers tend to be aware that the abstractions are just whatever they choose to make them and that they are not necessarily statements of absolute fact. In other introductory engineering contexts, at least in my experience, there is less of an explicit acknowledgment of the abstractions being used. Continued…

At the risk of sounding like I’m telling you to eat your vegetables, I’m going to zoom out one more step from the last post about units and talk even more generally about the importance of names. Whatever you think of Juliet’s famous answer, the reality is that if you want to get someone a rose, or even just to talk about a rose, you need to know what it’s called. Naming things is a very powerful human skill that allows us not only to better communicate our thoughts but to better form our thoughts in the first place. Continued…

How many volts of current are there in a bolt of lightning? That’s the kind of stupid question your local news anchor might ask while bantering with the weather guy. Perhaps your favorite cringe-inducing unit abuse is someone thinking light-years measure time or a model rocket enthusiast telling you that a newton-second is a little longer than a regular second. Of course, I made the same class of mistake when looking for a 1-amp battery, which I described in my previous post about battery capacity. That article addressed a specific instance of a general problem: not knowing or understanding units, which allow us to talk about and measure physical properties that we must understand whether we’re designing robots or baking cakes. Continued…

My earliest electronics projects and my first robot were powered by regular alkaline batteries, and I didn’t think about current or the capacity of those batteries. The batteries were prominently labeled “1.5V”, and I was happy in my understanding that putting four in a battery holder got me to 6 volts; when the motors slowed down, it was time for new batteries. When I began designing my second robot, I found some 12V, 1A motors (what a “1-amp motor” might mean is a topic for another post) and promptly wasted many hours dragging parents and teachers to Radio Shack and car parts stores looking for a 12V, 1A battery. Continued…

My name is Jan Malášek, which is a Czech name, so the “J” is pronounced as an English “Y” (if you care, we can go over the last name in person, or you can consult your local Czech person). I grew up on the Big Island of Hawaii, spent five years in school in Massachusetts, and then moved to Las Vegas, Nevada to work on Pololu. I recently turned 30, and I’m still not the millionaire I had hoped to become at age 23 and then by age 25. Hitting 30 means it has been twenty years since I got started with electronics and ten years since I routed the first circuit board that said “Pololu” on it. Continued…