Optical Shaft Encoder

Represent connected Optical Shaft Encoder and read relative position of motor shaft in ticks

• Library:

• Simulink Coder Support Package for VEX EDR V5 Robot Brain / Sensors

• 

Description

The Optical Shaft Encoder block represents an Optical Shaft Encoder that is connected to the 3-wire ports of VEX EDR V5 Robot Brain, and reads the relative position of the motor shaft in ticks. The value increments for anti-clockwise rotation and decrements for clockwise rotation of the motor shaft.

The tick count also depends on the Reset mode that you selected.

Ports

Input

Rst — Signal that resets the encoder reading

integer (0 = no reset; integer ≥ 1 = reset)

Connect to a signal that resets the Optical Shaft Encoder.

Dependencies

This input appears only when you set the Reset mode parameter to Reset by external signal.

Data Types: double

Output

Tick — Number of ticks read from Optical Shaft Encoder

tick count

The number of ticks that is read from the Optical Shaft Encoder connected to VEX V5 Robot Brain. One rotation corresponds to 360 ticks. The value increments for anti-clockwise rotation and decrements for clockwise rotation of the motor shaft.

Data Types: double

Parameters

Top port — 3-wire port to which the top port of Optical Shaft Encoder is connected

A (default) | C | E | G

Select the 3-wire port of VEX V5 Robot Brain to which the top port of Optical Shaft Encoder is connected. To know the top port, click the What is Top and Bottom Port? button.

After you select the Top port in the block, the consecutive 3-wire port is assumed to be connected to the bottom port of the encoder. For example, if you select A as the Top port, it is assumed that B is connected to the bottom port of the encoder.

Reset mode — Select the reset mode for reading values

Reset at each sample time (default) | No reset | Reset by external signal

Select the reset mode for reading values from the Optical Shaft Encoder.

When you select Reset by external signal, an additional input – Rst – is added to the block, which can be connected to a reset signal.

The different reset modes this block supports are as follows:

• No reset – The measurement value is not reset and the block outputs the total ticks of rotation.

  For example, in the table below at T = 1, the encoder moves a tick count of 20 in anti-clockwise direction and therefore the output is 20. Between T = 1 and T = 2, the encoder moves a tick count of 10.

  Therefore, the tick count is 30 at T = 2 ( 20 from T = 1 and 10 from T = 2). In this reset mode, the output at any time instant is a cumulative sum of the previous count and the current count.

• Reset at each sample time – For each sample period, the block outputs the measurement value and then resets it to 0.

  For example, in the table below, at T = 1, the encoder moves a tick count of 20 in anti-clockwise direction and therefore the output is 20. Between T = 1 and T = 2, the encoder moves a tick count of 10 and therefore the output is 10. In this reset mode, the output is the tick count at a particular time instant.

• Reset by external signal – The measurement value is reset to 0 based on the block input value. When you send a value other than 0 to the block input, the measurement value is reset to 0. For each sample period, the block outputs the measurement value since the last reset.

  For example in the table below, when the external signal is 0, the output is based on ‘No reset’ mode and when the external signal is non-zero, the output is based on ‘Reset at each sample time’ mode.

Sample time — Interval at which the block reads values

0.2 (default) | positive scalar | -1

Enter the time interval at which the block reads values from the Optical Shaft Encoder.

When you set this parameter to -1, Simulink^® determines the best sample time for the block based on the block context within the model. If you select Reset by external signal option in Reset mode parameter, the Sample time parameter is hidden and the value is inherited (Sample time = -1).

Introduced in R2019b