Cypress PSoC CY8CKIT-048, Manual

Page: 23 / 54

PSoC Analog Coprocessor Pioneer Kit Guide, Doc. # 002-11190 Rev. *B 23
Kit Operation
3.1.2 Analog Sensors
Analog sensors generally come in five different types, depending on their output electrical signal:
voltage, current, resistance, capacitance, or inductance. Each sensor type requires a specific AFE
design as shown in
Table 3-1 . The PSoC Analog Coprocessor provides resources to build all of
these AFEs, thus reducing the BOM cost and PCB size. The PSoC Analog Coprocessor contains
opamp, comparators, programmable gain amplifiers (PGA), programmable reference block (PRB)
and analog multiplexers (AMUX), which are the building blocks of different type of AFEs.
The remaining part of this section contains details of interfacing the PSoC Analog Coprocessor with
each of the sensors mentioned in
Table 3-1 . For example, Interfacing with a PIR Motion Sensor on
page 23 explains how to use opamps inside the PSoC Analog Coprocessor to implement a voltage
amplifier circuit.
3.1.2.1 Interfacing with a PIR Motion Sensor
The PIR motion sensor is based on the pyroelectric effect, where certain materials generate a
voltage when exposed to infrared radiation. This radiation is the portion of the electromagnetic
spectrum that falls between microwaves and visible light. Infrared radiation has wavelengths longer
than the visible light but shorter than microwaves. Humans at normal body temperature radiate
strongest in the infrared range at an approximate wavelength of 10 µm.
The PIR motion sensor uses infrared-sensitive materials as the sensing elements. It is packaged
with a field-effect transistor (FET) in the Source Follower mode, as
Figure 3-6 shows. An FET is
required to buffer the high-impedance output of the sensor element. When the sensor element is
exposed to infrared radiation, a voltage is generated across the element.
Figure 3-6. PIR Motion Sensor – Single-Element
Table 3-1. AFE Requirements for Different Sensors
Analog Sensor Output Signal AFE Sensor Part
PIR motion sensor (Refer to Interfacing
with a PIR Motion Sensor on page 23 )
Voltage Voltage amplifier Zilog ZRE200GE
Ambient light sensor (Refer to
Interfacing with an Ambient Light
Sensor on page 26
)
Current
Transimpedance
amplifier
Vishay TEMD6200FX01
Thermistor (Refer to Interfacing with a
Thermistor on page 27 )
Resistance
Programmable
voltage reference EPCOS (TDK)
B57164K103J
Inductive proximity sensor (Refer to
Interfacing with an Inductive Proximity
Sensor on page 28
)
Inductance
HPF-Down Mixer-
Rectifier
N/A (PCB trace)
Humidity sensor (Refer to Interfacing
with a Humidity Sensor on page 29 )
Capacitance
Charge transfer
circuit
HPP801A031