LED SEQUENCER

This circuit is the essence of many "chaser" schemes that provide animation in advertising displays, lighting ten LEDs sequentially.

Referring to the first schematic, U1 is a six-section inverting Schmitt trigger, with one section used as a relaxation oscillator. The other five sections of U1 aren't used, and their inputs are grounded. U1 drives the clock input of U2, a decimal counter. Each of the counter's ten outputs drive Darlington current buffers in U3 and U4, which, in turn, drive ten LEDs. The display's advancement rate is adjustable from about 5 to 140Hz with RV1.

The quantity of LEDs may be increased, most conveniently in multiples of ten, as illustrated in the second schematic. The arrangements of twenty and thirty LEDs utilize one common-anode resistor as in the first schematic. The forty-LED arrangement utilizes a series-parallel scheme, with two common-anode resistors, R4 and R5. In all cases, one-in-ten LEDs (or sets of LEDs) will be illuminated. (For example, in the forty LED arrangement, DS1, DS11, DS21, and DS31 all illuminate together.)

The specified LEDs are average-efficiency types that provide ample brightness for indoor applications. Given their typical forward-voltage characteristic of 2 volts, the anode resistors have been selected for a LED current of about 20 milliamperes. Other LEDs with a forward-voltage characteristic of 1.8 to 2.5 volts may be used.

Rectifier CR1 protects the circuit from accidental battery reversal. A 9-volt battery eliminator, such as TrIad type WSU090-0800 (Mouser stock number 553-WSU090-0800), is suggested for economical continuous operation.






Parts Table
(Updated July 3, 2016)

ITEM DESCRIPTION MANUFACTURER

MANUFACTURER
PART NUMBER

DISTRIBUTOR DISTRIBUTOR STOCK NUMBER
B1 9V BATTERY PANASONIC 6LF22XWA MOUSER 658-6LF22XWA
(Optional)9V BATTERY ELIMINATORTRIADWSU090-0800MOUSER553-WSU090-0800
C1 1uF, 35 VOLT RADIAL TANTALUM CAPACITOR KEMET T356A105K035AS MOUSER 80-T356A105K035
C2, C3, C4 0.1uF, 50 VOLT AXIAL CERAMIC CAPACITOR KEMET C420C104K5R5TA MOUSER 80-C420C104K5R
CR1 1 AMPERE, 50 VOLT AXIAL RECTIFIER VISHAY 1N4001GP-E3/54 MOUSER 625-1N4001GP-E3/54
DS1 - DS40 SIZE T1-3/4 DIFFUSED RED LED KINGBRIGHT WP7113ID MOUSER 604-WP7113ID
R1 10K, 1/4 WATT CARBON FILM RESISTOR XICON 291-10K-RC MOUSER 291-10K-RC
R2 270 OHM, 1/4 WATT CARBON FILM RESISTOR XICON 291-270-RC MOUSER 291-270-RC
R3, R4, R5 180 OHM, 1/4 WATT CARBON FILM RESISTOR XICON 291-180-RC MOUSER 291-180-RC
R6 91 OHM, 1/4 WATT CARBON FILM RESISTOR XICON 291-91-RC MOUSER 291-91-RC
RV1 250K TRIMMER POTENTIOMETER BOURNS 3386P-1-254LF MOUSER 652-3386P-1-254LF
S1 SPST SWITCH NKK M2011SS1W01 MOUSER 633-M201101
U1 HEX INVERTING SCHMITT TRIGGER IC, 14 PIN DUAL-INLINE PACKAGE TEXAS INSTRUMENTS CD40106BE MOUSER 595-CD40106BE
U2 DECIMAL COUNTER IC, 16 PIN DUAL-INLINE PACKAGE TEXAS INSTRUMENTS CD4017BE MOUSER 595-CD4017BE
U3, U4 SEVEN-SECTION DARLINGTON DRIVER IC, 16 PIN DUAL-INLINE PACKAGE ST MICROELECTRONICS ULN2004A MOUSER 511-ULN2004A
MISCELLANEOUS ITEMS:

IC SOCKETS
COMPONENT TERMINALS
WIRE
PERFORATED CIRCUIT BOARD
BATTERY CONNECTOR
(OPTIONAL) BATTERY ELIMINATOR JACK
MOUNTING HARDWARE
ENCLOSURE



May 11, 2004

Text and images 2004, 2012, 2016 by Arthur Harrison


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