Sensors play an important role in enabling the robot to communicate with its external environment or control its own system.
There are two basic types of digital sensors used in the development of robotic structures: analog and digital.
An analog sensor is designed to generate varying output signal over a wide range of measurements.
A digital sensor includes only two states, 'on' and 'off'. It is more complex and accurate digital sensor compared to the analog sensor.
The output of the digital sensor can exhibit different forms that include a serial interface, parallel interface or synchronous serial interface. A push button switch is one of the simplest forms of a digital sensor, and has two discrete values, 'on' or 'off'.
Digital sensors, unlike analog sensors produce discrete digital pulses according to the change in the environment.
These sensors transmit either zero voltage or maximum voltage instead of sending voltage between zero and maximum like the analog sensor.
If the microcontroller detects a voltage that is above or below the guaranteed levels, the results cannot be determined, and it can just be reported as high or low.
There are other digital sensors which output a series of digital pulses, or binary values. For instance, a digital sensor can output a 10 bit binary value 0000000000 to 1111111111 to notify a change, which means the sensor can produce one of 1024 values to induce a change in its environment.
Discrete signals typically have a stair step appearance when they are graphed on chart. Some digital sensors produce pulse trains of transitions between the 0 v state and the 5 v state. The frequency characteristics or shape of this pulse train provide the sensor's measurement.
The following are some of the major applications of digital sensors in robotic systems:
- They enable robots to be aware of the bumper on the front of the sensor being pushed.
- They serve as a limit switch sensor to check if the robot’s metal arm is in proper alignment.
Products on Market
Given below is the list of digital sensors that are currently being used in robotic systems:
Bumper Switch (2-pack)
The Bumper Switch developed by Vex includes a pair of simple bumper switches and ruggedized bumpers for allowing the switch to be triggered by large impacts without any sustainable damage.
The sensor maintains a digital high signal on its sensor port when the switch is not pushed in. The functionalities of this sensor can be pre-programmed in the VEX microcontroller.
DFRobot Digital Vibration Sensor
The DFRobot Digital Vibration Sensor developed by DFRobot is a digital plug and play sensor block that includes vibration switch digital input module and sensor expansion boards.
This digital sensor device has the capability to sense weak vibration signals that can be realized using shock interaction. The switch to this component is ideal for a small-current circuit or an integrated circuit of the trigger.
Sources and Further Reading