Electronics for Artists - Chapter 9 (sensors)

This is a break down about sensors:

A sensor is a type of switch that can activate something.

Sensor types:
1. Heat
2. Light
3. Sound
4. Position
5. Movement
6. Direction of movement
7. Speed of movement

Terms:
1. WIRED OR: sensors (with switch outputs) connect with a signal giving sensor that operates a switch.

2. Open switch: there is no connection to the ciruit until something is detected.

3. Closed switch: there is no connection until something is detected (the connection is interupted).

PIRs (passive infrared):

- they have a typical range of 6m
- they can sense a large area
- sensor can be altered to sense a smaller area if lens is painted (test with paper before painting because it is irreversable)

- type 1: used for turning on lights and can have timers. They can increase power outputs.
- type 2: used for burglar alarms and are versitile because they can be hooked up to anything.

Temperature:

- variable resistance types:

- non-precision thermistors (temperature sensitive resistors)
- positive temperature coefficient: resistance increases with temperature.
- negative temperature coeffient: resistance decreases with temperature.

Light:

1. Light dependant resistors: changes resistance with amount of light falling on it.
2. Photovoltaic cell: produces voltage according to light seen.

Infrared light beam:

have a range of approximately 10m

types:
1. pulse (turns of and off quickly).
2. light sensor that detects a break in the beam.

LEDs are the best because they increase intensity and they have a narrow angle (which is easier to control).

note: incandescent lamp and sunlight produce infrared light that can interfere

Sound:

types of frequency:
1. audible (range of 20Hz to 16KHz)
2. infrasound (lower frequency)
3. ultrasound (higher frequency)

- sound can travel through both air and materials

mic types:

1. air vibration mics (regular mics)
2. piezoelectric sensors (contact mics)

vibration :

- found in car alarm systems
- operate on a pulse system and turn on and off depending on frequency of vibration
- contact mics can be used as a vibration sensor

Proximity and touch:

types:
1. PIRs
2. Ultrasonic radar
3. Infrared
4. Capacitive

-Capacitive sensor:
- can detect a small or large area
- a cheap and easy to use
- can be made from metal material (as long as grounded)
-operate through a reed switch