Optical encoder board

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The optical encoder board is an electronic schematic that holds optical sensor. The sensor is of type "Transmissive Optical Sensor with Phototransistor Output", e.g.: Vishay Semiconductors TCST1103, TCST1202 or TCST1300.

Optical encoder used in current schematic - is an incremental encoder with two sensors, which optical axes are allocated 90 degrees out of phase to detect the direction of rotation - this is so called quadrature scheme (refer to: http://en.wikipedia.org/wiki/Rotary_encoder#Incremental_rotary_encoder). In cases, where there is a need in determining zero point (for camera rotation, or controlling wheel direction) there is one additional sensor, scanning the second (outer) track, which contains only one line, indicating initial position (zero point).

Because it was hard to find a sensor, which is initially designed to determine direction, it was decided to use only simple and wide spread sensors with only one output.

Contents

Variations

Version 2

This version is based on Honeywell HOA0901-011 sensor, which provides means for plain low-effort quadrature encoding reader.

File:HOA0901-11.pdf
File:HOA0901-11 appnote.pdf

Version 1

Board Type1 (Motion Primary)

Encoder can read one track of encoding disk (external or internal). Output signal is amplified on-board, and other signals from nearby Type2 boards if any is also amplified by the same circuit. All amplified signals are then retransmitted to motor control circuit.

Schematic capture

Encoder can read one track of encoding disk (external or internal). Signal is amplified.

PCB Layout

Large PCB (Type 1) of the motion encoder, with buffering IC (74HC14):

Encoder can read one track of encoding disk (external or internal). Signal is amplified.

Device photo

Device photo of the optical encoder Type1

Board Type2 (Motion Secondary)

Encoder can read one track of encoding disk (external or internal). Output signal then flows to nearby Type1 board, amplified/filtered, and retransmitted by wires to motion control circuit. There may be one or two Type2 boards around one Type1 board, depending on the purpose (one board is used for quadrature encoding, another scans zero point track, which gives some initial position, from which it starts angle counting).

Schematic capture

Encoder can read one track of encoding disk (external or internal)

PCB Layout

Small sensor PCB (Type 2) of the motion encoder, without buffering:

Encoder can read one track of encoding disk (external or internal)

Device photo

Device photo of the optical encoder Type2

CamV Encoder (Pitch)

Optical encoder board for vertical camera positioning. PCB with four mounting holes and three sensors (CamV) and with buffering IC (74HC14).

Encoder can read vertical camera position incrementally (by scanning index track), report direction (by providing quadrature-coded signal pair) and zero point (separate index and zero tracks).

Schematic capture

Encoder can read vertical camera position incrementally, and report direction and zero point.

PCB Layout

Encoder can read vertical camera position incrementally, and report direction and zero point.

Device photo

Device photo of the vertical camera encoder board.

See also

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