In this episode of The Engineering Commons, we discuss an electromechanical component commonly used to achieve physical motion; the ubiquitous direct-current (DC) motor.
Carmen admits to getting turned on by electricity… and sugar!
Although differencesbetweenenginesandmotors can be argued, at least one definition claims that an engine converts chemical energy to mechanical energy, while a motor converts electrical energy to mechanical energy.
DC motors are powered with direct current, while AC motors are powered with an alternating current.
Carmen mentions an app note (pdf) on Brushless DC motors by MPS (Monolithic Power Systems).
Although linear motors will not be covered in this episode, their operation is similar to that of rotational motors.
The two major categories for DC motors are brushed and brushless; the two major categories for AC motors are synchronous and induction (asynchronous).
When describing a motor’s mechanical components, the portion that rotates is the rotor, while the portion that remains stationary is the stator.
Brian notes that Nikola Tesla’s induction motor may be his most significant invention.
In induction motors, slip is percentage difference between the rotational speed of the magnetic field and that of the rotating shaft.
In 1832, William Sturgeon produced the first practical DC motor.
An H-bridge is an electronic circuit that allows a DC motor to run forwards or backwards.
In many cases, a pulse-width modulation (PWM) signal can be used to control motor speed. This is accomplished by turning motor power on and off at a high frequency, while maintaining a desired ratio of “on” time to “off” time.
When describing a motor’s electrical components, the portion that carries the current is called the armature, while the portion that generates the magnetic flux is called the field.
An electrical charge passing through a magnetic field is subject to a mechanical force, known as a Lorentz force. A conductor (wire) carrying current through a magnetic field can thus be levitated by this force.
DC motor behavior is described by several motor constants, including the torque constant and the back-EMF constant.
A commutator periodically reverse the flow of current through an external circuit. In a brushed DC motor, this is accomplished mechanically.
Brushes deliver voltage to the commutator, and are often spring loaded against the commutator segments.
In mechanical systems, rotational power is the product of torque and angular velocity.
Brushless DC motors often use Hall effect sensors to detect when power should be switched to a different armature winding.
A stepper motor advances by a fixed rotational angle each time it receives an input pulse.
Enterprising engineers can play music with stepper motors!
Thanks to Les Chatfield for use of the photo titled “At speed!” Opening music by John Trimble, and concluding theme by Paul Stevenson.
We are joined once more by Dave Goldberg, author of A Whole New Engineer, to discuss the critical engineering skills of noticing, listening, and questioning.
Brian takes a 50/50 shot at guessing whether President Lincoln faces left or right on the United States one-cent coin.
For younger listeners, Jeff describes the features of a telephone keypad, once a common element of everyday life. He also waxes nostalgic about telephone directories.
Our guest for this episode is Dave Goldberg, founder and president of ThreeJoy Associates, Inc., who leads us in a discussion of noticing, listening, and questioning (NLQ).
Noticing, in the context of our conversation, is less about recalling fine details, and more about remaining open to alternate interpretations of one’s thoughts, emotions, and sensory inputs.
Dave proposes that the three domains of noticing are language, emotion, and body.
Brian asks if noticing is hindered by pareidolia, the mind’s tendency to assign meaning to random patterns.
Jeff makes a reference to “hippie,” which may be a new term for younger listeners.
Dave explains differences between Level 1 and Level 2 listening.
Asking open-ended questions that begin with “What” can elicit more meaningful responses from others. (Avoid questions starting with “Why,” as they may be interpreted as judgemental.)
Dave can be reached through the website for his consulting firm, ThreeJoy Associates, the website for his book, A Whole New Engineer, or via email: deg511 -=+ at +=- gmail -=+ dot +=- com.
Thanks to Flavio~ for use of the photo titled “Before it Started Barking.” Notice any similarity between the dog’s nose and the ironwork? Opening music by John Trimble, and concluding theme by Paul Stevenson.
Our guest is Dave Vandenbout, an electrical engineer who founded XESS Corporation twenty-three years ago. Dave also has experience as an engineering professor and industrial researcher.
In Episode 103, Ones and Zeros, Dave explained the various types of programmable logic devices available to electronic designers.
Our guest notes that, in his experience, industrial organizations tend to be hierarchical and well-funded, while academic organizations tend to be relatively flat and less well-funded.
In academic circles, an overhead rate is the percentage of research funding that goes directly to the university to pay for supporting services that are not directly related to the research effort.
Jeff notes similarities in the experiences encountered by entrepreneurs and newly-employed professors.
Carmen notes a blog and podcast by Jon Ellis (a.k.a. Prof. Gears) that discusses the ups and downs of life as a tenure-track academic.
On average, Dave found a student’s grade point average (GPA) to be a poor predictor of research performance.
Although once rare in the engineering field, more and more engineering PhDs are taking jobs as postdoctoral researchers (post-docs) in preparation for academic careers.
In the United States, most tenure-track academics start their careers as Assistant Professors.
Tenure is a contractual right, granted by an academic organization, that provides legal protection against dismissal without just cause.
After six years, assistant professors not granted tenure are asked to leave the university (normally after a one year appointment). Those receiving tenure are often promoted to the position of Associate Professor.
Full Professor (or just Professor) is the top academic rank at most universities.
An h-index is a numerical ranking that attempts to measure an academic’s influence and contribution within a research field.
Dave comments that every graduate student wants to be a professor, and every professor wants to be a graduate student.
A recent Science Magazine article notes that only two of five influential cancer studies could be replicated.
Thanks to U.S. Army RDECOM for use of the photo titled “Army scientist bolsters nanomaterials research with Singapore.” Opening music by John Trimble, and concluding theme by Paul Stevenson.
In this episode of The Engineering Commons, we discuss an electromechanical component commonly used to achieve physical motion; the ubiquitous direct-current (DC) motor.
