Distance Flashcards
Most popular distance sensor?
Ultrasonic distance sensor
Two common ways to measure distance?
Sound echoes and light reflection
What can an ultrasonic sensor provide?
Exact distance from sensor to person
How does Infra red (IR) sensor work?
It detects the heat radiated by living things, can not measure exact distance
What’s the difference between active and passive infrared sensor?
Active IR sensor: it sends out invisible light and see if it is reflected back; it can tell whether an object is closer than a certain distance; some rare cases gives exact distance reflected from ir light
Passive IR sensor: measures heat radiated from infra red light
How are long distances measure?
Long distance range finders use laser beam to measure distance
Factors speed in which light is reflected back
Expensive
How does ultrasonic sensor work? What are its three pins?
Works by measuring distance it takes for sound signal to echo back
Signal, Ground, 5V power
At what temperature does sound travel faster and why?
Warm temperatures, air particles already vibrating with heat
What affects speed of sound (r)? Provide formula
Temperature; v= (331.3+ 0.606*T) m/s
What’s the name of ultrasonic sensor with four pins?
HC-SR04; different pin to send out pulse and listen for echo
Advantages and disadvantages of picking IR over ultrasonic sensor?
+: Soft objects absorb the sound waves sent out by ultrasonic sensor so not enough echo to detect object while IR is able to detect the object
-: can’t measure distance
How to make Piezo beeper?
Using piezoelectric crystal that changes shape when voltage is applied to it; using alternating current (AC) or on-off square wave will cause it to vibrate which vibrates the air causing sound
How to create a square wave in arduino?
By turning off and on the digital pin using digital write
Square wave varies between HIGH 5v and LOW 0v
