Intro to Sensors
Limit Switches
A limit switch is a device that detects the presence, absence, or position of an object by opening or closing an electrical circuit when a physical force is applied to its actuator (like a lever or button).
The Thifty Bot sells a normally closed version of this called the Thrifty Hall Effect, which is a contactless magnet-based limit switch that is omnidirectional with an LED for user feedback. For more info, see the product page here.
Uses:
Position Sensing: Detects when the system reaches the end of its range.
Safety: Stops motors if the system they control moves into an unsafe position.
Protection: Prevents parts from moving too far and getting damaged.
Quadrature Encoders
Quadrature encoders are sensors that measure the position, speed, and direction of a rotating object using two signals that are 90 degrees apart.
How They Work:
Signal Generation: The rotating shaft produces two square waves.
Direction Detection: The order of the signals shows which way the shaft is turning.
Position Counting: Counts the pulses of the signals to determine position.
Resolution: More pulses per revolution mean more accurate measurements.
Absolute Encoders
Absolute encoders provide a unique position value for each shaft angle, ensuring that the exact position is always known, even after a power cycle.
PWM Index Pin Absolute Encoders
These encoders use Pulse Width Modulation (PWM) to convey position information. The position is encoded in the width of the pulses generated by the index pin.
How They Work:
Signal Generation: The encoder generates pulses with varying widths corresponding to the shaft's position.
Position Detection: The width of the PWM signal is measured to determine the exact position of the shaft.
Uses:
Precise Positioning: Ideal for applications requiring accurate and repeatable positioning. Think about controlling a swerve module's rotation or an arm's position.
Analog Absolute Encoders
These encoders provide position feedback as a continuous analog signal, typically a voltage or current that varies linearly with the position.
The Thrifty Bot sells one of these, and more info can be found at the product page here.
How They Work:
Signal Generation: The encoder produces a continuous analog signal (in the Nova's case, 0-3.3V) proportional to the shaft position.
Position Detection: The control system reads the analog signal to determine the exact position.
Continuous Feedback: Provides smooth and continuous position information.
Uses:
Precise Positioning: Ideal for applications requiring accurate and repeatable positioning. Think about controlling a swerve module's rotation or an arm's position.
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