Design And Construction Of A Running Message Display LED Circuit

ABSTRACT

 Light emitting diodes are advantageous due to their smaller size, low current consumption and catchy colours they emit. In this work a running message display circuit is designed wherein the letters formed by LED arrangement light up progressively. Once all the letters of the message have been lit up, the circuit gets reset. The circuit is built around Johnson decade counter CD4017BC (IC2). One of the IC CD4017BE’s features is its provision of ten fully decoded outputs, making the IC ideal for use in a whole range of sequencing operations. In the circuit only one of the outputs remains high and the other outputs switch to high state successively on the arrival of each clock pulse.

 Description

Light emitting diodes are advan- tageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of the message have been lit up, the circuit gets reset. The circuit is built around Johnson decade counter CD4017BC (IC2). One of the IC CD4017BE’s features is its provision of ten fully decoded outputs, making the IC ideal for use in a whole range of sequencing operations. In the circuit only one of the outputs remains high and the other outputs switch to high state successively on the arrival of each clock pulse. The timer NE555 (IC1) is wired as a 1Hz astable multivibrator which clocks the IC2 for sequencing operations. On reset, output pin 3 goes high and drives transistor T7 to ‘on’ state. The output of transistor T7 is connected to letter ‘W’ of the LED word array (all LEDs of letter array are connected in parallel) and thus letter ‘W’ is illuminated. On arrival of first clock pulse, pin 3 goes low and pin 2 goes high. Transistor T6 conducts and letter ‘E’ lights up. The preceding letter ‘W’ also remains lighted because of forward biasing of transistor T7 via diode D21. In a similar fashion, on the arrival of each successive pulse, the other letters of the display are also illuminated and finally the complete word becomes visible. On the following clock pulse, pin 6 goes to logic 1 and resets the circuit, and the sequence repeats itself. The frequency of sequencing operations is controlled with the help of potmeter VR1.

 Circut Diagram:

The display can be fixed on a veroboard of suitable size and connected to ground of a common supply (of 6V to 9V) while the anodes of LEDs are to be connected to emitters of transistors T1 through T7 as shown in the circuit. The above circuit is very versatile and can be wired with a large number of LEDs to make an LED fashion jewellery of any design. With two circuits connected in a similar fashion, multiplexing of LEDs can be done to give a moving display effect 1N4148 signal diode

A schematic symbol for a diode

1N4148 diodes in DO-35 glass-encapsulated axial lead package

The 1N4148 is a standard silicon switching signal diode. It is one of the most popular and long-lived switching diodes because of its dependable specifications and low cost. Its name follows the JEDEC nomenclature. The 1N4148 is useful in switching applications up to about 100 MHz with a reverse-recovery time of no more than 4 ns.

Contents

• 1 Overview
• 2 Specifications
• 3 See also
• 4 References
• 5 External links

Overview

As the most common mass-produced switching diode, the 1N4148 replaced the older 1N914. They differ mainly in their leakage current specification, which at 25°C is:

• 1N914: 25 nA at -20 V
• 1N4148: 5 µA at -75 V^[1]

Maximum leakage for both types at 150°C is 50 µA at -20V.

Today manufacturers produce the 1N4148 and sell it as either part number.^[2] It was second-sourced by many manufacturers; Texas Instruments listed their version of the device in an October 1966 data sheet.^[3] These device types have an enduring popularity in low-current applications.^[4][5]

The JEDEC registered part numbers 1N4148 and 1N914 are diodes in an axial package. Diodes with similar properties are available in surface-mount packages.

Through-hole package

• 1N4148 in DO-35 glass axial package.^[6][7][8]

Surface-mount packages

• LL4148 in MiniMELF package.^[9]
• 1N4148W in SOD-123 package.^[10][11][12]
• 1N4148WS in SOD-323 package.^[13][14]
• 1N4148WT in SOD-523 package.^[15][16]

Note: Some surface-mount packages are marked with “T4” text.^[10][11]

Specifications

Absolute maximum ratings (stress ratings, consult datasheet for recommended ratings)^[6]

• V_RRM = 100 V  (maximum repetitive reverse voltage)
• I_O = 200 mA  (average rectified forward current)
• I_F = 300 mA  (DC forward current)
• I_f = 400 mA  (recurring peak forward current)
• I_FSM = 1 A at 1 s pulse width; 4 A at 1 µs pulse width (non-repetitive peak forward surge current)

Electrical and thermal characteristics^[6]

• V_F = 1 V at 10 mA (maximum forward voltage)^[17]
• V_R = 75 V at 5 µA; 100 V at 100 µA (minimum breakdown voltage and reverse leakage current)
• t_rr = 4 ns (maximum reverse-recovery time)
• P_D = 500 mW (maximum power dissipation)

See also

• Diode logic
• 1N400x general purpose diodes
• 1N58xx schottky diodes

References

• 1N914 Datasheet; DO-35 Package; Vishay.
• · Michael Predko (2004). 123 robotics experiments for the evil genius. McGraw-Hill Professional. p. 93. ISBN 978-0-07-141358-9.
• · The Transistor and Diode Data Book, Texas Instruments Incorporated, publication no. CC-413 71243-73-CSS, no date, page 10-34
• · Jonathan Oxer; Hugh Blemings (2009). Practical Arduino: Cool Projects for Open Source Hardware. Apress. p. 10. ISBN 978-1-4302-2477-8. Small “signal” diodes like the venerable 1N4148/1N914 can cope with about 200mA…
• · Michael Gasperi; Philippe E. Hurbain; Philippe Hurbain (2009). Extreme NXT: Extending the Lego Mindstorms NXT to the Next Level (2nd ed.). Apress. p. 211. ISBN 978-1-4302-2453-2. You could use a 1N4002, but the 1N4148 is smaller and more appropriate for the current…
• “1”. The Semiconctor Data Library (Fourth ed.). Motorola Semiconductor Products, Inc. 1973. p. 73.