LED Sequencer Circuit

Descrete Multistage Light Sequencer Circuit
The drawing below illustrates a multistage light sequencer using
descrete parts and no integrated circuits. The idea is not new
and I hear a similar circuit was developed about 40 years ago
using germanium transistors. The idea is to connect the lights so
that as one turns off it causes the next to turn on, and so forth.
This is accomplished with a large capacitor between each stage
that charges when a stage turns off and supplies base current to
the next transistor, thus turning it on. Any number of stages can
be used and the drawing below illustrates 3 small Christmas lights
running at about 5 volts and 200mA. The circuit may need to be
manually started when power is applied. To start it, connect a
momentary short across any one of the capacitors and then
remove the short. You could use a manual push button to do this.

16 Stage LED Sequencer Circuit
The circuit below uses a hex Schmitt Trigger inverter (74HC14)

and two 8 bit Serial-In/Parallel-Out shift registers (74HCT164 or

74HC164) to sequence 16 LEDs. The circuit can be expanded to

greater lengths by cascading additional shift registers and

connecting the 8th output (pin 13) to the data input (pin 1) of the

succeeding stage. A Schmitt trigger oscillator (74HC14 pin 1 and 2)

produces the clock signal for the shift registers, the rate being

approximately 1/RC. Two additional Schmitt Trigger stages are

used to reset and load the registers when power is turned on.

60 Light Sequencer Circuit using a Matrix

The circuit below illustrates using a 10x10 matrix to sequence up

to 100 LEDs with just three ICs and 20 transistors. The two 4017

decade counters control the 10 rows and 10 columns so that one

LED is selected depending on the output of the decade counters.

The LED circuit is drawn showing 25 LEDs and 10 transistors but

can be expanded up to a 100 by using sucessive stages of the

4017 counters.

more

LED sequencer
The model 4017 integrated circuit is a CMOS counter with ten

output terminals. One of these ten terminals will be in a "high"

state at any given time, with all others being "low," giving a

"one-of-ten" output sequence. If low-to-high voltage pulses are

applied to the "clock" (Clk) terminal of the 4017, it will increment

its count, forcing the next output into a "high" state. With a 555

timer connected as an astable multivibrator (oscillator) of low

frequency, the 4017 will cycle through its ten-count sequence,

lighting up each LED, one at a time, and "recycling" back to the

first LED. The result is a visually pleasing sequence of flashing

lights. Feel free to experiment with resistor and capacitor values

on the 555 timer to create different flash rates

more