1. PH4705 & ET4305: Digital Sensors
Simple switches to data words
Switch: micro-switch, reed relay, Hall sensor, optical switch…..
Threshold or Set point detector
Counting, timing, finding the frequency
Sensors that generate data words directly
Complex IC sensors that generate serial data or connect to a bus system

2. PH4705 & ET4305: Digital Sensors
Switch
Input ON/OFF information
mechanical movement
micro-switch,
reed relay operated by a magnet
Hall effect sensor

3. PH4705 & ET4305: Digital Sensors

4. PH4705 & ET4305: Digital Sensors
Switch
Light Beams
LDR-light dependant resistor
Photo-diode
Photo-transistor
Slotted and reflective sensors

5. PH4705 & ET4305: Digital Sensors

6. PH4705 & ET4305: Digital Sensors
Logic Signal input
ON/OFF input
Compatible logic signal (voltage levels, available current)?
Interference and noise?

7. PH4705 & ET4305: Digital Sensors
Threshold or Set Point Detection
Analogue input signal, detect when its value passes through a set point or threshold (in either direction)

8. PH4705 & ET4305: Digital Sensors
Input
Zero crossing detector
Output
Potential
Divider Sets
Threshold
Threshold or Set Point detector
Threshold detector with hysteresis

9. PH4705 & ET4305: Digital Sensors
Counting, timing, finding frequency
The required data derived from switch sensors may be:
number of pulses
time between pulses
width of pulse
frequency of pulses ………..

10. PH4705 & ET4305: Digital Sensors
Data Words
Typical example is this optical coded disc used to detect angular position. Looking along a radius gives an 8-bit word or a resolution of 1/256.
(Looking at the pulse rate of, say, the outside markings will also yield speed.)

11. PH4705 & ET4305: Digital Sensors
Complex IC digital sensor
Sensors system ICs that have signal processing and generate digital data as a serial data streams or connect directly to a microprocessor system data bus.
Examples: CCD digital camera sensor,
SHT75 temperature/humidity module

12. PH4705 & ET4305: Digital Sensors