Electronic Research - Designing A Digital Letter Box
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DESIGNING A DIGITAL LETTER BOX D.H.M. Perera 042039
History of Communication
Communication is the method which people
share
their
ideas
and
information.
At early stages, the man communicate through mails using, - runners, - pigeons - by using arrows with letters
History of Com………
The need of letters occurs as a media of communication.
Mailing system - first introduced by Britain - began to deliver the mails to the houses - need of letter boxes occurs to keep letters
Necessity of Digital letter box
Modern world is becoming very busy - People like to do their activities easily and save the time . - people does not like to waist their time for small things
New Digital Letter Box is needed to detect the presence of letters easily
The normal operation of Digital Letter Box
When no letters are present
The normal operation of Digital Letter Box
When letters are present
Block Diagram Of The Designed Circuit Light Source
•
Detect Light/Dark
Light Source
To Display - Two colors LEDs
– A LED or a Bulb can be used
• Detect Light / Dark
– A LDR
• Display
– Two LEDs can be used
A Circuit should be implemented to obtain above operations.
Implementing The Circuit
The circuit was designed using a NE555 IC
Most Common Operations of NE555 are, - Monostable - Astable &
NE555 IC as an Inverting Buffer
Inverting buffer - the output logic state (low/high) is the inverse of the input state
•
Input low (< 1/3 Vs) makes output high, +Vs
•
Input high (> 2/3 Vs) makes output low, 0V
Output remains in its present state, When
the
input
voltage
is
NE555 IC as an Inverting Buffer
Gives the input a high immunity to noise
In other way we can say, •
High Output – Trigger input must go to higher to a lower level.
•
Low Output - The higher output can be returned to a lower by causing the threshold to go from a lower to a higher
NE555 IC as an Inverting Buffer
When, Vin < 1/3 Vsupply - High Output Vin > 2/3 Vsupply - Low output
Voltage Trigger
to
Threshold
X
To Trigger/Threshold
To give the required output, At illumination LED)
X < 1/3
Supply
- High Output (Red
At dark (Green LED)
X > 2/3
Supply
- Low output
&
The designed circuit
The circuit at Letter Box,
The designed circuit
The circuit at house,
Procedure of the Experiment
Main controlling part – voltage divider circuit with LDR •
LDR resistance value at Dark
≈ 4.0 MΩ
•
LDR resistance value at Light
≈ 2.3 kΩ
The Resistance of LDR was observed, •
Using a 6 V bulb / white LED as the light source
History of Communication
Communication is the method which people
share
their
ideas
and
information.
At early stages, the man communicate through mails using, - runners, - pigeons - by using arrows with letters
History of Com………
The need of letters occurs as a media of communication.
Mailing system - first introduced by Britain - began to deliver the mails to the houses - need of letter boxes occurs to keep letters
Necessity of Digital letter box
Modern world is becoming very busy - People like to do their activities easily and save the time . - people does not like to waist their time for small things
New Digital Letter Box is needed to detect the presence of letters easily
The normal operation of Digital Letter Box
When no letters are present
The normal operation of Digital Letter Box
When letters are present
Block Diagram Of The Designed Circuit Light Source
•
Detect Light/Dark
Light Source
To Display - Two colors LEDs
– A LED or a Bulb can be used
• Detect Light / Dark
– A LDR
• Display
– Two LEDs can be used
A Circuit should be implemented to obtain above operations.
Implementing The Circuit
The circuit was designed using a NE555 IC
Most Common Operations of NE555 are, - Monostable - Astable &
NE555 IC as an Inverting Buffer
Inverting buffer - the output logic state (low/high) is the inverse of the input state
•
Input low (< 1/3 Vs) makes output high, +Vs
•
Input high (> 2/3 Vs) makes output low, 0V
Output remains in its present state, When
the
input
voltage
is
NE555 IC as an Inverting Buffer
Gives the input a high immunity to noise
In other way we can say, •
High Output – Trigger input must go to higher to a lower level.
•
Low Output - The higher output can be returned to a lower by causing the threshold to go from a lower to a higher
NE555 IC as an Inverting Buffer
When, Vin < 1/3 Vsupply - High Output Vin > 2/3 Vsupply - Low output
Voltage Trigger
to
Threshold
X
To Trigger/Threshold
To give the required output, At illumination LED)
X < 1/3
Supply
- High Output (Red
At dark (Green LED)
X > 2/3
Supply
- Low output
&
The designed circuit
The circuit at Letter Box,
The designed circuit
The circuit at house,
Procedure of the Experiment
Main controlling part – voltage divider circuit with LDR •
LDR resistance value at Dark
≈ 4.0 MΩ
•
LDR resistance value at Light
≈ 2.3 kΩ
The Resistance of LDR was observed, •
Using a 6 V bulb / white LED as the light source
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