When you must track motion, you’ll need a shaft encoder, or rotary encoder. Most of these sensors use a circular disk placed between an LED light source and a phototransistor light detector. Depending on the type of encoder you need, the disk can produce X pulses per revolution or a binary-coded output.An incremental encoder produces a quadrature output that indicates rotation direction and produces a series of pulses you can count. In some cases, this type of encoder includes an index output that produces a short pulse once per revolution. An absolute encoder supplies information in coded form that tells you the shaft’s actual position. You can specify the type of code–usually binary of gray code. Read more at www.ecnmag.com/rotary-encoders-take-the-shaft.aspx. In addition to determining position, you can use an encoder’s output to measure rotation speed.While looking for an incremental shaft encoder I discovered one that uses a capacitance sensor to detect position. This type of sensor can help reduce power in equipment–6 mA at 5V down to 3.2 mA at 3V. You can find brief descriptions of the AMT-102 and -103 encoders at the www.amtencoder.com web site. The parent company, CUI, uses a custom ASIC to sense capacitance changes in an RF circuit and to convert that information into position increments.
According to the AMT site: …electronics use a 5-MHz signal modulated with a 10-kHz signal for sensing the position of the rotor by measuring the phase between the receiver low-frequency modulation and the transmitter low-frequency modulation. The sensor output has a small lag time as shaft rotations accelerate or decelerate.The AMT sensors let users change DIP-switch settings to choose one of 16 resolution that can range from a high of 2048 pulses per revolution (PPR) at 7500 RPM down to as low as 48 PPR at 30,000 RPM. You don’t have that flexibility with an optical encoder. You can buy the AMT-102 and -103 sensors from Digi-Key for $US 29.95 each, (part numbers 102-1307-ND and 102-1308-ND respectively) so it doesn’t cost much to give them a try. Each encoder comes with a variety of shaft adapters that range from 2 to 8 mm in diameter and include 1/8-, 3/16-, and 1/4-inch sizes.
When you visit the AMT Web site, be sure to read the inventor’s biography. It’s nice to see that information and more companies should tell engineers about their creative colleagues. –Jon Titus
Advertised as the "Most Powerful Tablet Under $100," the Kindle Fire HD 6 was too tempting for the team at iFixit to pass up. Join us to find out if inexpensive means cheap, irreparable, or just down right economical. It's teardown time!
The increased adoption of wireless technology for mission-critical applications has revved up the global market for dynamic electronic general purpose (GP) test equipment. As the link between cloud networks and devices -- smartphones, tablets, and notebooks -- results in more complex devices under test, the demand for radio frequency test equipment is starting to intensify.
Much of the research on lithium-ion batteries is focused on how to make the batteries charge more quickly and last longer than they currently do, work that would significantly improve the experience of mobile device users, as well EV and hybrid car drivers. Researchers in Singapore have come up with what seems like the best solution so far -- a battery that can recharge itself in mere minutes and has a potential lifespan of 20 years.
Some humanoid walking robots are also good at running, balancing, and coordinated movements in group settings. Several of our sports robots have won regional or worldwide acclaim in the RoboCup soccer World Cup, or FIRST Robotics competitions. Others include the world's first hockey-playing robot and a trash-talking Scrabble player.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.