WATER LEVEL CONTROLLER
USING 555 TIMER
By,
Department of TCE/ECE
JNNCE , Shimoga
OBJECTIVE:
•
Automatic Control of AC Motor
Thus Preventing overflow from
Over Head Tank.
OVERVIEW :
AC
MOTOR
OVER HEAD TANK
M
Upper
CIRCUIT BOARD
Lower
GND
CIRCUIT BOARD BLOCK DIAGRAM:
Input From OHT
555 TIMER
IC
DRIVER
RELAY
CIRCUIT DIAGRAM:
ABOUT THE 555 TIMER IC
• Introduced in 1972 by Hans Camenzind
at Signetics Corporation. Low cost , stable , low power.
• Manufactured 1 billion units / year .
• 8 pin mini DIP-8 pack.
• Includes 25 Transistors ,2 diodes and 15 resistors
in silicon chip.
• Used in timer , pulse generation and Oscillator applications .
Pin Details:
1 – GND : Ground, low level (0 V)
2 – TRIGGER : Detects 1/3Vcc, Output high. Pin 2
controls over Pin 6.
3 - OUTPUT :This output is driven to approximately
1.7V below +V cc or GND
4- RESET
:A timing interval may be reset by driving
this input to GND
5 – CONTROL : Control access to the internal
voltage divider (by default, 2/3 VCC).
6 – THRESHOLD : The interval ends when the voltage at
THRESHOLD is greater than at CONTROL.
7 - DISCHARGE : Open collector output; may discharge
a capacitor between intervals.
8- VCC
: Positive supply voltage.( 3 to 15V)
Specifications of NE555:
1) Supply Voltage : 3 to 15 V
2) Supply Current : 3 to 15 mA
3) Output Current : 200mA (MaX)
4) Power Consumption : 225 mW @ 15V
Modes of Operation:
1) Astable
: Free Running mode, used as oscillator ,
provide time delay, adjust duty cycle.
2) Monostable : "one-shot" pulse generator.
Applications include timers,
bounce free switches.
3) Bistable
: Basic flip-flop , Schmitt trigger.
CIRCUIT DIAGRAM:
555 ANALYSIS :
+
-
+
-
TRUTH TABLE : (SR FLIP FLOP)
SET(S)
RESET(R)
Action
0
0
HOLD
STATE
0
1
RESET(0)
1
0
SET(1)
1
1
NOT
ALLOWED
WATER CONTROLLER TRUTH TABLE :
Pin 2
Pin 6
Output
Low
Low
High
Low
High
No change
High
Low
Not Valid
High
High
Low
+
-
+
-
*When Water Below LOWER LEVEL :
Comparator 1 = high
Comparator 2 = Low
SR FLIP FLOP = SET (1) , Q bar ( OUTPUT ) = Low (DRIVES THE
RELAY)
*When Water Level Reaches UPPER LEVEL:
Comparator 1= Low
Comparator 2= High
SR FLIP FLOP = RESET (0) , Q bar (OUTPUT) =High ( RELAY OFF)
WORKING ANALYSIS:
MOTOR SWITCHES “ON”
MOTOR SWITCHES “OFF”
RELAY : An Electromagnetic Switch
Relay Open :
Common - Normally
closed (NC)
Relay Closed :
Common – Normally
open (NO)
LIST OF COMPONENTS REQUIRED:
COMPONENTS
PARTICULARS
QUANTITY
IC
NE555
1
IC-BASE
8 PIN
1
RESISTORS
1M ,10K
2,2
CAPACITORS
1uF , 0.01uF
1,1
DIODE
1N4007
1
TRANSISTOR
BC548,SL100
1,1
GENERAL PCB
2*3 INCH
1
DC JACK
FEMALE
1
12V ADAPTER
SMPS
1
PCB RELAY
12 V
1
An Astable Circuit has no stable state - hence the name "astable".
The output continually switches state between high and low
without any intervention from the user, called a 'square' wave.
This type of circuit could be used to give a mechanism intermittent
motion by switching a motor on and off at regular intervals. It can
also be used to flash lamps and LEDs, and is useful as a 'clock' pulse
for other digital ICs and circuits.
A Monostable Circuit produces one pulse of a set length in
response to a trigger input such as a push button. The output of
the circuit stays in the low state until there is a trigger input, hence
the name "monostable" meaning "one stable state
A Bistable Mode or a Schmitt Trigger, has two stable states, high
and low. Taking the Trigger input low makes the output of the
circuit go into the high state. Taking the Reset input low makes the
output of the circuit go into the low state. A push button would be
placed at each end of the track so that when one is hit by the train,
it will either trigger or reset the bistable.