Welcome to the Pololu Blog, where we provide updates about what we and our customers are doing and thinking about. This blog used to be Pololu president Jan Malášek’s Engage Your Brain blog; you can view just those posts here.
This video shows a heavily-modified 3pi that uses distance sensors and encoders along with a flood-fill algorithm to find the shortest path through a walled Micromouse maze. The robot is described in more detail in this forum post.
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…
This small hexapod using the Micro Maestro is controlled remotely using a Bluetooth module. Very detailed build information is available in this blog post.
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…
Groovin’ Grover is a marionette manipulated by four hobby servos and a Pololu Maestro servo controller. You can control each of Grover’s limbs independently and make him walk, wave, and – most entertainingly – make him dance. Groovin’ Grover is easy to assemble and wire up. This Instructable explains how to build your own Groovin’ Grover.
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.
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…
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