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This is a spectacular but completely
useless project. It lights Ultra-Bright LEDs in a
sequence and each LED flashes brightly very briefly. The
LEDs light-up going around and around since they are
mounted in a circle (on a CD), then they pause before
chasing again. The very brief flash of each LED (15ms)
and the pauses (1 second) reduce the average current so
the battery should last a long time.
For user convenience, this project has a
stepper speed control and a brightness control. At
slower speeds and/or reduced brightness, the batterys
life is extended considerably.
At full brightness, the LEDs flash
extremely brightly. More than one of this project
grouped together occasionally synchronize, lighting the
whole room for a moment.
At maximum speed, the LEDs dont 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.
Click here to view Circuit
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Battery: Four AA alkaline cells.
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Battery life:
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Minimum speed and brightness 2.3 years
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Medium speed and brightness 1 year
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Minimum speed, maximum brightness 4.1
months
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Maximum speed and brightness 3.8 weeks
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Brightness: controlled with Pulse width
Modulation, from off to extremely bright (4000mcd).
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Stepper speed: 2 LEDs/sec to 2
revolutions/sec.
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Pulse Width Modulation frequency:
3.9KHz.
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LED current: 24mA pulses.
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LED voltage drop: 3.2V at 24mA. Blue,
green and white Ultra-Bright LEDs are suitable.
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Minimum battery voltage:
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<3V, oscillators do not run.
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3V, LEDs are very dim.
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4V, LEDs reach almost full brightness.
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Radio interference: none.
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The 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.
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The 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 switching.
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IC2 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 positive
supply.
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IC1 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.
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IC1 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.
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IC1 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.
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IC1 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.
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IC1 pins 13 and 12 is an inverter that
resets the counter/decoder and shuts-off the clock
oscillator through D4, during the pause time.
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IC1 pins 9 and 8 is not used and is
shut-off by grounding its input.
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T1 is the PWM switching transistor. R9
limits the maximum LED current to 24mA.
The 10 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.
If you turn it down each night, its
current is so low an on-off switch isnt needed.
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.
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