At maximum speed, the LEDs don’t appear
to flash, instead they appear to move from one lighted
one to the next, around and around. They rotate
completely for 4 rotations in two seconds, and then turn
off for a one second pause then repeat the sequence. At
a lower speed, the number of rotations before the pause
is less. It will do three rotations, two or even only
one rotation at its slowest speed. A sequence of
rotations starts with LED #2 and end with LED #9.
Battery: Four AA
Minimum speed and brightness
Medium speed and brightness
Minimum speed, maximum brightness 4.1
Maximum speed and brightness 3.8 weeks
Brightness: controlled with Pulse width Modulation, from off to
extremely bright (4000mcd).
Stepper speed: 2
LEDs/sec to 2 revolutions/sec.
Width Modulation frequency: 3.9KHz.
current: 24mA pulses.
voltage drop: 3.2V at 24mA. Blue, green and white Ultra-Bright
LEDs are suitable.
<3V, oscillators do not run.
3V, LEDs are very dim.
4V, LEDs reach almost full brightness.
CD74HC4017N high-speed Cmos IC is rated for a maximum supply
voltage of 7V. It is rated for a maximum continuous output
current of 25mA. In this project, the maximum supply voltage
is 6.4V with brand new battery cells and the 24mA output
current is so brief that the IC runs cool.
MC14584BCP* IC (Motorola) is an ordinary “4XXX series” 3V to
18V Cmos IC, with a very low operating current and low
output current. Its extremely high input resistance allows
this project to use high value resistors for its timers and
oscillators, for low supply current. Its 6 inverters are
Schmitt triggers for simple oscillators and very quick
is a 10 stage Johnson counter/decoder. On the rising edge of
each clock pulse its outputs step one-at-a-time in sequence.
It drives the anode of each conducting LED toward the
pins 1 and 2 is a Schmitt trigger oscillator with C3 and C4
paralleled for a very low frequency. R1 and R2 control its
frequency and the diodes with R3 combine with the capacitors
to produce the 15mS on time for the LEDs.
pins 5 and 6 is the brightness Pulse Width Modulation
oscillator. The pot R7 with the associated diodes and
resistors allow it to change the duty-cycle of its output
for PWM brightness control. It drives the transistor.
pins 3 and 4 is an inverter. It takes the low time (LEDs
off) from the clock oscillator, inverts it to a high and
shuts-off the brightness oscillator through diode D6.
pins 11 and 10 is a sample-and-hold stage. It takes a sample
of the pulse driving LED #9 though D3 and R4 and charges C5
in steps. At maximum speed it takes 4 steps for C5 to charge
to the Schmitt switching threshold voltage. R5 and D5 slowly
discharge C5 for the pause time.
pins 13 and 12 is an inverter that resets the
counter/decoder and shuts-off the clock oscillator through
D4, during the pause time.
pins 9 and 8 is not used and is shut-off by grounding its
is the PWM switching transistor. R9 limits the maximum LED
current to 24mA.
LEDs mount on a Compact-Disc which is glued to a plastic box
with contact cement. The box houses the Veroboard circuit in its
lower main part with the battery holders on its lid.
Multiconductor ribbon cable joins the LEDs to the circuit. The
pots mount on the sides of the box.
turn it down each night, its current is so low an on-off switch
1 IC1 MC14584BCP (Motorola) * Ordinary Cmos hex
Schmitt trigger inverters
1 IC2 CD74HC4017N High-speed Cmos decade counter/decoder
1 T1 2N3904 or 2N4401 NPN transistor
8 D1 to D8 1N4148 or 1N914 Diodes
10 LEDs Blue, green or white Ultra-Bright LEDs with Vf = 3.2V or
less at 20mA
1 R1 100K 1/4W resistor
1 R2 1M Linear-taper potentiometer
1 R3 33K 1/4W resistor
1 R4 2.2M 1/4W resistor
1 R5 22M 1/4W resistor
1 R6 47K 1/4W resistor
1 R7 1M Audio-taper (logarithmic) potentiometer
1 R8 1.8K 1/4W resistor
1 R9 68 ohms 1/4W resistor
1 C1 100uF/16V Electrolytic capacitor
1 C2 0.1uF/50V Ceramic capacitor
2 C4 and C4 1uF/63V Metalized poly capacitor
1 C5 470nF Metalized poly capacitor
2 C6 and C7 1nF Metalized poly capacitor
* A CD74C14 can also be used for IC1 but R4 = 1M,
R5 = 10M, C3 and C5 = 330nF, C4 = 470nF.
A 3V LED Chaser project also works well with these changed parts
but using a CD74HC14N for IC1.
In addition to these changes, R8 = 680 ohms and R9 = 22 ohms. I
built one using low-voltage (1.8V at 20mA) orange Ultra-Bright
LEDs. The orange one looks good beside the green one.
Attachments: 6V LED Ultra-Bright Chaser schematic, Veroboard
layout and 3 pictures.
I wish I knew how to take a slow picture with my son’s digital
camera, so all the LEDs would be lighted, and if I moved it
would make nice lighted smears in the picture.