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...

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...

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

We see that this sampling rate essentially correctly "maps" the waveform, introducing some phase shift error. Depending on where sampling occurs this error may be as high as just under 90 electrical degrees, but does not directly give you 4X the frequency.

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