The 8051 Microcontroller and Embedded

Department of Computer Science and Information EngineeringNational Cheng Kung University

21

INTERFACING TO ADC AND SENSORSTesting ADC804(cont’) HANEL

5V 10kPOT

VCCRDCLK RWRCLK inD0Vin (+)D1D2Vin (-)D3D4/2VrefD5CSD6D7D GNDINTRA GND

8051 ADC804P2.5P2.6P1.0 P1.7P2.7

10k 150 pF

8051 Connection to ADC804 with Self-Clocking

Department of Computer Science and Information EngineeringNational Cheng Kung University

22

INTERFACING TO ADC AND SENSORSADC804 Clock from 8051 XTAL2 HANEL

5V CLK inCLK R10kVin (+)POTVin (-)V/2refCS A GND

VCCP2.5RDP2.6WRP1.0D0D1D2D3D4D5D6D7P1.7GNDINTRP2.7

XTAL1XTAL2

QD Q DQ Q

8051

ADC804

74LS74

The frequency of crystal is too high, we use two D flip-flops to divide the frequency by 4
8051 Connection to ADC804 with Clock from XTAL2 of 8051

Department of Computer Science and Information EngineeringNational Cheng Kung University

23

‰INTERFACING TO ADC AND SENSORSInterfacing Temperature Sensor HANEL

A thermistor

responds to temperature

change by changing resistance, but its response is not linear‰The complexity associated with writing software for such nonlinear devices has led many manufacturers to market the linear temperature sensor

1.700

75

0.817

100

3.893

50

10.000

25

29.490

0

Tf (K ohms)

Temperature (C) From William Kleitz, digital Electronics

Department of Computer Science and Information EngineeringNational Cheng Kung University

24

INTERFACING TO ADC AND SENSORS HANEL

LM34 and LM35 Temperature Sensors

‰The sensors of the LM34/LM35 series are precision integrated-circuit temperature sensors whose output voltage is linearly proportional to the Fahrenheit/Celsius temperature¾The LM34/LM35 requires no external calibration since it is inherently calibrated¾It outputs 10 mV for each degree of Fahrenheit/Celsius temperature