NETAJI SUBHAS INSTITUTE OF

TECHNOLOGY

EC-316 Microprocessor Lab Project

RESISTOR TESTER

By: Sahishnu (150/EC/13)

Sandeep Sahu (155/EC/13)

SYNOPSIS

Resistor is another component an Electronics Engineer or an Electrician use in

day to day life. It is the basic component present in every electronic circuit. No

material is ideal. Every material has some value or percentage of error. But

these errors may influence your Electronic Circuit, so it’s very important to

evaluate tolerance of a Resistor while choosing Resistors. This is what we are

doing in this Project. This is an effort to determine the value of the actual

resistance of the known resistor with its tolerance. The user has to place the

resistor in the space provided on the pcb and has to slide the corresponding

button in the dip switch provided at the right corner on the board. If the keys

slides correctly according to value of the resistor then on the lcd the resistance

will be displayed with the tolerance.

ACKNOWLEDGEMENT

Firstly we would like to thank Prof. Dhananjay Gadre for his unconditional

support and thorough guidance without which this project would not have seen

the light of the day. He not only guided us through the project but also played a

vital role in helping us relate the theoretical concepts with their practical

concepts and instilled in us enthusiasm to LEARN BY DOING. This project

was definitely a milestone in our career and we learnt a lot more than just

electronics, values of hard work and team work.

We would also like to thank our friends and classmates especially Vaibhav and

Sachin Demla who worked with us and helped at each and every point of time

we needed help and assistance. From helping us learn EAGLE, guiding to get

PCB ready, helping us through the soldering sessions, getting corrections in

code and also final checks on the project and what not, they were always with

us. It was a really good memorable experience working with all of them.

We would also like to thank all the staff of the Department of Electronics of

Netaji Subhas Institute of Technology for providing us with all the requisites for

completion of this project.

CONTENTS

1) Introduction

2) Project description

I) Hardware implementation

II) 24bit ADC (HX711)

III) Block diagram

IV) Component required

3) Schematic files

I) Full schematic

II) Voltage sense circuit

III) 8155 interface with LCD and DIP SWITCH

4) Working pictures and processes

5) Testing and compensation

6) Gant chart revisited

7) Flow chart

8) Conclusion

9) Bibliography

INTRODUCTION

A resistor is a passive two-terminal electrical component that

implements electrical resistance as a circuit element. All of us have

been came across the same problems that the value of resistor

required for a high precision value are very hard to find. Their actual

value varies from the value that has been obtained by decoding the

band on it. Their tolerance is of range 1%,5%,10%and 20%. The

reason behind their variation is the manufacturing condition. For a

particular batch their tolerance is nearby same. Our project is based

on 8085 ( 8 bit microprocessor ) through which we have interfaced a

lcd ,24bit precision adc (HX711) and other peripherals(

8155,Ram,.ROM and etc.). 24bit adc provides the serial data with the

clock(square) modified to operate at 80us delay and 8085 receives the

data through SID pin. Then through internal coding in 8085 it process

the data and provides the output at the lcd .

PROJECT DESCRIPTION

Hardware implementation

1) To determine the voltage across the known resistor the opamp has been used in

the voltage follower condition and to reduce the gain of 128 in the adc we have

further used an opamp in the non-inverting gain condition whose gain is

1/128.(fig 1)

2) The output of the 2nd opamp has been given as an input to the ADC(HX711).

3) The LCD and dip switch has been interfaced using 8155. This has 3 ports (port

A and port B with 8 data line and port C with 6 data line). Here port A has been

used as an input port for dip switches and port B(8 line ) and port C(MSB line

5,4,3) has been used as an output fort for lcd command and data output.

4) ADC has been provided with the modified clock from the 8155 clock registers

in square wave generating mode with 80us total time period.

5) ADC provides data according to the clock and 8085 receives data through SID

pin.

6) Then 24 bit data has been in complementary form it is converted in to normal

form and various algorithm works on it to provide data at the output to the lcd.

HX711 24 BIT ADC MODULE

HX711 is a precision 24-bit analog to-digital converter (ADC) designed for weigh

scales and industrial control applications to interface directly with a bridge sensor. The

input multiplexer selects either Channel A or B differential input to the low-noise

programmable gain amplifier (PGA). Channel A can be programmed with a gain of 128

or 64, corresponding to a full-scale differential input voltage of ±20mV or ±40mV

respectively, when a 5V supply is connected to AVDD analog power supply pin.

Channel B has a fixed gain of 32. On chip power supply regulator eliminates the need

for an external supply regulator to provide analog power for the ADC and the sensor.

Clock input is flexible. It can be from an external clock source, a crystal, or the on-chip

oscillator that does not require any external component. On-chip power on-reset

circuitry simplifies digital interface initialization. There is no programming needed for

the internal registers. All controls to the HX711 are through the pins.

BLOCK DIAGRAM

COMPONENTS REQUIRED

S. NO. COMPONENTS USED

QUANTITY/

SPEC.

1. 8085 MPU 1

2. SRAM(62256) 1

3. EEPROM(28256) 1

4. Latch(74573) 1

5. 3X8 Active Low Decoder(74138) 2

6. NOR Gate IC(7402) 1

7. LED(3MM, red, green) 2

8. Resistors 85,100,150,1k,10k,128k

9. Electrolytic Capacitors 10uF,100uF

10. Ceramic Capacitors 22pF,0.01uF

11. Quartz crystal 6Mhz

12. Dip Switches 8 1

13. LCD 1

14. 8155 1

15. HX711 24 bit ADC 1

SCHEMATIC FILES

1) Full schematic

2) voltage sensing ckt

3) 24bit ADC(HX711) interface

4) Power supply and IC

5) 8155 interface with lcd and dip switch

Working pictures and processes

TESTING AND COMPENSATION

1) Testing ADC HX711 using Arduino uno for its 24 bit serial output data

using voltage sensing circuit developed. This process went fine and able to

receive data.

2) Testing 8085 peripheral IC 8155 for the output and input ports with LCD

and DIP SWITCHES. LCD worked perfectly.

3) Written codes for SID/Sod and uploaded it on ROM through ROM

programmer provided by CEDT lab. The SID/SOD worked perfectly.

4) Written codes for LCD , Dip Switches and HX711 on JUBIN 8085 simulator

IDE. Lcd AND Dip switches worked fine but not able to receive data from

hx711 (ADC).

5) Tested the connections and double checked the schematic but nothing

worked out for ADC

6) Written code for Binary to BCD conversion, LCD display 24*24bit

multiplication , 24 bit by 24 bit division, remainder calculation and

tolerance worked perfectly with if the data was provided by us in the

memory specified where 24bit ADC data has to be stored.

GANTT CHART REVISITED

PROJECT ACTIVITY ACTUAL

COMPLETION ANTICIPATED COMPLETION

Introduction to 8085 7-Jan-16 7-Jan-16

Familiarity with pin diagram and

function 10-Jan-16 10-Jan-16

Deciding partners 4-Jan-16 4-Jan-16

Go through projects on internet 14-Jan-16 10-Jan-16

Develop the concept of our project 12-Jan-16 12-Jan-16

Get approval 4-feb-16 4-feb-16

Studying of 8085- interfacing and

hardware 10-Feb-16 15-Feb-16

Review of CAD software EAGLE 1-feb-16 10-feb-16

Schematic development 5-Mar-16 25-Feb-16

Routing and development of PCB 25-Mar-16 8-Mar-16

Soldering the components 27-Apr-16 15-Apr-16

Learn assembly language programming 25-Mar-16 27-Mar-16

Develop the assembly language code 3-Jun-16 25-Apr-16

Integration of software and hardware 1-Jun-16 1-May-16

Testing and validation 3-Jun-16 3-May-16

Documentation 2-Jun-16 20-Apr-16

FLOW CHART A

A

CONCLUSION

During this project we have worked a lot to make this happened. This is one of

the projects that can remain in our heart for long. We have gone through various

difficulties and overcome them either ourselves or with the help of our friends

and especially by Prof. Gadre. We thank sir for giving us such an opportunity.

The various difficulties that rose were, unable to get the serial data from the 24

bit ADC and conversion of 24 data from complementary form to normalised

form so that other algorithm could be applied on that data and hence to obtain

the final result.

The working of this project was totally dependent on the mutual understanding

between us we have to agree on the same fact so we can proceed further on our

project. It took little time but finally project has come to the existence. We hope

that our work will be utilized by some other juniors to make out with the

difficulties that we were unable to resolve.

And hopes that our project works fine on the day and forever.

BIBLIOGRAPHY

TEXTBOOKS: 1. Microprocessor Architecture, Programming, and Applications with the 8085 Author: Ramesh Gaonkar Publisher: Penram International Publishing (India) Pvt. Ltd Edition: 5th edition ISBN: 9788187972099

DATASHEETS PROVIDED BY PROF. GADRE https://drive.google.com/folderview?id=0ByFqcybodzN8LS1PRTliN1lSdUU&usp=sharing

PROJECT LINK ON DRIVE

https://drive.google.com/folderview?id=0B841_wY-dWHJYk5nQkNsUm9xbEU&usp=sharing

RESOURCES LINKS

http://www.sunrom.com/p/loadcell-sensor-24-bit-adc-hx711

https://www.classle.net/#!/classle/content-page/divide-16-bit-number-8-bit-number-

microprocessor-8085/

http://microprocessorforyou.blogspot.in/2011/12/memory-interfacing-in-8085.html

http://www.slideshare.net/shashank03/8085-architecture-memory-interfacing1

http://www.sunrom.com/c/products

https://books.google.co.in/books?id=AVRvAwAAQBAJ&pg=PA27&lpg=PA27&dq

=interfacing+lcd+with+8085&source=bl&ots=80VIH1HyK6&sig=i7tmg-

R6sFXb2kjChVL4tm0w6xk&hl=en&sa=X&ved=0ahUKEwiC0qzJibTLAhUIGo4KH

U8MDM44PBDoAQgaMAA#v=onepage&q=interfacing%20lcd%20with%208085&f

=false