Ladder Logic to decode direction from an Optical Encoder

April 15, 2014

I set up a QR145 optical encoder on a Direct Logic DL06 PLC with some simple ladder logic to determine direction based on the A and B incremental inputs. below is a video of the optical encoder in action: In the PLC I used (DL06), the inputs are filtered, which...

Optical Encoder Incremental Signal Measurement

March 26, 2014

While most of us are familiar with how to measure something in mechanical degrees, incremental optical encoder signals are measured in electrical degrees. 360 electrical degrees is the period in which a signal completes one high to low transition.  This can be in any sort of waveform, but for encoders...

How to time Optical Encoder commutation channels to a BLDC motor

March 17, 2014

Optical Encoder Brushless DC Motor timing using Back EMF The optical encoders we work with have a set of three Commutation tracks (U,V,W) which correspond to the three phases of the motor (R,S,T). Alignment of the Optical encoder commutation signals to a BLDC motor could be thought of as being...

Why Use an Optical Quadrature Encoder for a Motor Encoder?

February 22, 2014

What is the purpose of an Optical Quadrature Encoder on the back of a motor? Incremental Optical Encoders will often provide commutation “Hall signals” for timing of the BLDC windings, but I am going to forgo that discussion and turn instead to the Incremental Encoder channels, specifically A and B...

Understanding Options on the QDH20 Industrial Rotary Encoder.

November 20, 2013

The QDH20 is an IP66 sealed encoder made for the rugged duty of an industrial application.  Due to the huge array of configuration options, this optical encoder has over 200,000  possible ways that it can be configured. While this is certainly an advantage to an end user that may be...

Better Edge Determination for Rotary Encoders.

September 14, 2013

A standard edge sensing scheme for optical rotary encoders is to square up the raw analog sine wave by comparing it against a given voltage.   If your analog signal has a 2Vpp amplitude, the value at which you switch off of, creating the edges of your square waves, could be...

E-mail on Creating a Post Quad Encoder signal

August 13, 2013

Below is an e-mail response I sent to someone who was asking about how to calculate the sampling rate they needed to 4X encoder signals.  4Xing or “Post Quad” is a way to use the fundamental A and B encoder pulses to get a higher line count. I wasn’t sure...

Reduce electrical noise in rotary incremental encoders with termination resistors

June 10, 2013

Since most electronics are set up to have high input impedance, in some situations the addition of a loading or “termination” resistor can help to reduce interference from electrical noise. This can be of particular help when implementing an incremental encoder where there is a long cable run.  If the...

Interlaced Sensor Technology in Rotary Incremental Encoders.

May 13, 2013

. If you search the web for a rotary encoder tutorial on incremental encoder construction, the simplest two channel A & B style encoders talk about a light source and a single photo receptive element for each channel.  The light beam of this optical pair is then interrupted by the...

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