WEEK 7

with 

BISMILLAHIRRAHMANIRRAHIM

INTRODUCTION

In this week, i am analyzing the characteristic from previous week, where in here, i am doing some practical observation and calculation. All the characteristic's behavior with the theory i had referred to my supervisor to ask her explanation. Aided by her, i gain the details all about my circuit work. All the note i add in my log book/ note. Some  pictures of the result i put here to show how i am taking the result.

 THE ANALYSE

In this analyse, the calculation, observation and practical had been made. But not all of the circuit i can made in practical as my equipment are limitation.

COMPARATOR

Below the diagram of the output waveform and the circuit of comparator

The Vol and Voh is taken from data sheet. the data sheet is too large to put in this site
Vref is the Voltage referance where it need to constant in voltage divider while Vin is the Voltage input come from Voltage divider from LDR.
To increase the sensitive value of the circuit, at Vref i put the variable resistor which it can be change the value of  voltage divider.

calculation in log book

MONOSTABLE

Below the diagram of the output waveform and the circuit of monostable

The duration of the pulse is called the time period (T) and this is determined by resistor R1 and capacitor C1

time period , T = 1.1xR1xC1

The maximum reliable time period is about 10 minutes as the capacitor charge to 63% so it bit longer than time sonstant (R1xC1) which time taken charge to 63%

choose C1 first (there are relatively few values available)
choose R1 to give the time period i needed. R1 should be in range 1k ohm to 1M ohm, so the fixed  resistor can of at least 1k ohm in series if R1 is variables
 electrolytic capacitor values are not accurate, errors of at least 20% are common
electrolytic capacitors leak charge which substantially increase the time period if im using high value resistor

ASTABLE

Below the diagram of the output waveform and the circuit of astable

The time period (T) of the square wave is the time for one complete circuit cycle, but usually better to consider frequency (f) which the number of the cycle per second.

for the timer

T= 0.7 x(R1 +2R2) xC1

for the frequency

f= 1.4/ ((R1 +2R2)xC1)

the times periods can be split into two parts T = Tm + Ts

Tm = mark time (output high)

Ts = space time (output low)

choosing  R1, R2 and C1

R1 and R2 should be in the range 1k ohm and 1M ohm. its the best choose C1 first because capacitors are available in just a few values

choose C1 to suit the frequency range i require (by refer the table below)

choose R2 to give frequency (f) i require. Assume that R1 is much smaller than R2 (so that Tm and Ts are almost equal), the use the formula to calculate it

R2 =0.7/fC1

LDR (LIGHT DEPENDENCE RESISTANCE)

Electrical characteristic (table below)

Here the result from my own experiment of LDR by using 12V battery

SCHEMITT TRIGGER

the Schemitt trigger only use a couple transistor as a switch. but in this project i just try two transistor only