Sensor interfacing in 8051
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The document discusses various techniques for interfacing microcontrollers to sensors, including analog interfaces using analog-to-digital converters to read sensor output voltages and convert them to digital values. It provides examples of interfacing microcontrollers to temperature sensors like the LM34 and LM35, whose output voltage varies linearly with temperature, and to ADC0848 and ADC0804 analog-to-digital converters. The document also includes code to read temperature sensor values using an ADC0848 converter and display the results on an 8051 microcontroller's port pins.
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Sensor interfacing in 8051
- 2. Microcontroller to Sensor Interfacing Techniques GROUP MEMBERS IRFAN AHMAD MUHAMMAD JUNAID MUHAMMAD ISHAQ ALAM NASIR
- 3. Micro-controllers are useful to the extent that they communicate with other devices, such as sensors, motors, switches, keypads, displays, memory and even other micro-controllers Many microcontroller designs typically mix multiple interfacing methods. In a very simplistic form, a microcontroller system can be viewed as a system that reads from (monitors) inputs, performs processing and writes to ( controls ) outputs.
- 4. Input Devices Microcontroller Output Devices
- 10. Thermistors
- 11. LM34 and LM35 Temperature Sensors The sensors of the LM34/LM35 series are good integrated-circuit temperature sensors whose output voltage is linearly proportional to the Fahrenheit/Celsius temperature The LM34/LM35 requires no external calibration since it is inherently calibrated It outputs 10 mV for each degree of Fahrenheit/Celsius temperature
- 14. 8051 Connection to ADC0848 and Temperature Sensor ADC0804 is a very commonly used 8-bit analog to digital convertor. It is a single channel IC, i.e., it can take only one analog signal as input. The digital outputs vary from 0 to a maximum of 255. The step size can be adjusted by setting the reference voltage at pin9. When this pin is not connected, the default reference voltage is the operating voltage, i.e., Vcc. The step size at 5V is 19.53mV (5V/255), i.e., for every 19.53mV rise in the analog input, the output varies by 1 unit. To set a particular voltage level as the reference value, this pin is connected to half the voltage. For example, to set a refer ence of 4V (Vref), pin9 is connected to 2V (Vref/2), thereby reducing the step size to 15.62mV (4V/255).
- 15. QUESTION? Q1 Q2
- 16. ADC808 has 8 analog inputs It allows us to monitor up to 8 different transducers using only a single chip The chip has 8-bit data output just like the ADC804 The 8 analog input channels are multiplexed and selected according to table below using three address pins, A, B, and C
- 17. 8051 Connection to ADC804 and Temperature Sensor
- 18. Getting Data From the Analog World
- 19. Noise considerations Many sensors, such as thermocouples, generate a relatively small voltage so noise is always an issue. The most common source of noise is the utility power lines (50 Hz or 60 Hz). Typically, the bandwidth for temperature sensors is much lower than 50 or 60 Hz so a simple low-pass
- 20. FOR GROUNDING
- 21. Program:Code to read temp from ASC0848,convert it to decimal,and put it on P0 with some delay?. #include<reg51.h> bit RD=P2^5; Sbit WR=P2^6; sbit E=P2^7; Sfr MYDATA=P1; Void ConvertAndDisplay(unsigne d char value); Void MSDelay(unsigned int value); Void main() { MYDATA =0xFF; E=1; RD=1; WR=1; While(1) { WR=0; WR=1; While(INTR==1); RD=0; Value=MYDATA; ConvertAndDisplay(value); RD=1; } } Id ConvertAndDisplay(unsigned char value) { Unsigned char x,d1,d2,d3; X=value/10; d1=value%10; d2=X/10; d3=X/10; P0=d1; MSDelay(250); P0=d2; MSDelay(250); P0=d3; MSDelay(250); } Void MSDelay(unsigned int value) { unsigned char x,y; For(x=0;x<value;x++) For(y=0;y<1275;y++); }